This document provides an overview of Nuclear Magnetic Resonance Spectroscopy (NMR). It discusses key topics such as nuclear spin, magnetic moments, precession, resonance frequency, absorption lines, relaxation times, and factors that influence line broadening. The document is intended to introduce students to the basic theory, principles, and applications of NMR spectroscopy.
This document provides an overview of instrument validation and calibration techniques. It discusses the definitions of calibration and validation, highlighting that calibration demonstrates an instrument produces results within specified limits compared to a reference standard, while validation establishes that an analytical procedure meets requirements for intended use. The need for regular calibration of instruments is explained, including after installation, time periods, shocks, or questionable observations. Methods for calibrating an infrared spectrophotometer are presented, including verifying wave numbers and resolution performance against tolerance limits. Applications of infrared spectroscopy like structure determination and identification are also mentioned.
Spin-spin splitting is a term that describes the magnetic interactions between neighbouring, non-equivalent NMR-active nuclei which will cause splitting of NMR signal. This splitting occurs because of the interaction between neighboring hydrogen nuclei, and results in multiplets rather than single peaks in the NMR spectrum. The number of peaks in the multiplet is predicted by the "n+1" rule, where n is the number of neighboring equivalent protons. Common splitting patterns include doublets, triplets and quartets.
The document discusses atomic absorption spectroscopy. It begins with an introduction describing how atomic absorption spectroscopy measures the concentration of an element by measuring the amount of light absorbed at a characteristic wavelength when it passes through atoms of that element. It then describes the principle, instrumentation, applications, and sources of interference in atomic absorption spectroscopy. The key sources of interference discussed are non-spectral interferences such as matrix, chemical, and ionization interferences and spectral interferences such as background absorption.
NMR spectroscopy(double resonance, C 13 NMR, applications)Siddharth Vernekar
Nuclear magnetic double resonance (NDMR) involves applying two radiofrequency signals during an NMR experiment. This allows decoupling of signals from different nuclei, resulting in simplified spectra. NDMR techniques include varying the magnetic field or radiofrequency while keeping the other constant. 13C NMR is useful in organic structure elucidation since 13C is spin active unlike 12C. NMR spectroscopy determines structure by analyzing how nuclei reorient in an external magnetic field and the energy changes involved. Its primary applications are structure determination, qualitative and quantitative analysis of mixtures, and studying phenomena like hydrogen bonding and molecular interactions.
This document discusses nuclear magnetic resonance (NMR) spectroscopy. It begins by describing the basic components of an NMR spectrometer, including a magnet, sample holder, radio frequency generator, detector, and reader. It then discusses the importance of using deuterated solvents like CDCl3 in NMR to minimize background signals. The document also explains the two main nuclear relaxation processes in NMR - spin-lattice and spin-spin relaxation. Additional sections cover factors that influence chemical shifts like electronegativity and anisotropic effects. Finally, the document provides examples of the number of NMR signals expected for different compounds based on equivalent and non-equivalent protons.
1. Spin-spin splitting occurs when nonequivalent protons on the same carbon or adjacent carbons interact with each other magnetically. This causes peaks in NMR spectra to split into multiplets.
2. The number of peaks in a multiplet is determined by the "n+1" rule, where n is the number of protons on adjacent carbons. For example, two adjacent protons cause a doublet, three adjacent protons cause a triplet.
3. The intensities of peaks within multiplets follow Pascal's triangle, such as a triplet having peak intensities of 1:2:1. This is because of the different magnetic environments felt by the absorbing proton due to the alignments of adjacent protons.
Mass spectrometry deals with studying charged molecules and fragment ions produced from a sample exposed to ionizing conditions. It provides the relative intensity spectrum based on ions' mass to charge ratio, allowing identification of unknown compounds. The document discusses the basic principles, advantages, disadvantages, instrumentation, applications, and analysis techniques of mass spectrometry.
Calibration - UV VIS Spectrophotometer, HPLC, Gas Chromatograph, IR spectroph...SELINA SRAVANTHI
Calibration of analytical instruments is important to ensure accurate measurements. It involves comparing instruments to more precise reference standards. Calibrating UV-Vis spectrophotometers involves checking wavelength accuracy using holmium filters, absorbance accuracy using potassium dichromate, stray light levels, resolution, and linearity. Calibrating IR spectrometers involves checking wavenumber accuracy using polystyrene, resolution, transmittance levels, linearity, and reproducibility. Calibrating fluorimeters involves setting excitation/emission wavelengths and adjusting the concentration readout using standards. Calibrating HPLCs involves checking flow rate accuracy and gradient performance using solvent mixtures.
This document provides an overview of instrument validation and calibration techniques. It discusses the definitions of calibration and validation, highlighting that calibration demonstrates an instrument produces results within specified limits compared to a reference standard, while validation establishes that an analytical procedure meets requirements for intended use. The need for regular calibration of instruments is explained, including after installation, time periods, shocks, or questionable observations. Methods for calibrating an infrared spectrophotometer are presented, including verifying wave numbers and resolution performance against tolerance limits. Applications of infrared spectroscopy like structure determination and identification are also mentioned.
Spin-spin splitting is a term that describes the magnetic interactions between neighbouring, non-equivalent NMR-active nuclei which will cause splitting of NMR signal. This splitting occurs because of the interaction between neighboring hydrogen nuclei, and results in multiplets rather than single peaks in the NMR spectrum. The number of peaks in the multiplet is predicted by the "n+1" rule, where n is the number of neighboring equivalent protons. Common splitting patterns include doublets, triplets and quartets.
The document discusses atomic absorption spectroscopy. It begins with an introduction describing how atomic absorption spectroscopy measures the concentration of an element by measuring the amount of light absorbed at a characteristic wavelength when it passes through atoms of that element. It then describes the principle, instrumentation, applications, and sources of interference in atomic absorption spectroscopy. The key sources of interference discussed are non-spectral interferences such as matrix, chemical, and ionization interferences and spectral interferences such as background absorption.
NMR spectroscopy(double resonance, C 13 NMR, applications)Siddharth Vernekar
Nuclear magnetic double resonance (NDMR) involves applying two radiofrequency signals during an NMR experiment. This allows decoupling of signals from different nuclei, resulting in simplified spectra. NDMR techniques include varying the magnetic field or radiofrequency while keeping the other constant. 13C NMR is useful in organic structure elucidation since 13C is spin active unlike 12C. NMR spectroscopy determines structure by analyzing how nuclei reorient in an external magnetic field and the energy changes involved. Its primary applications are structure determination, qualitative and quantitative analysis of mixtures, and studying phenomena like hydrogen bonding and molecular interactions.
This document discusses nuclear magnetic resonance (NMR) spectroscopy. It begins by describing the basic components of an NMR spectrometer, including a magnet, sample holder, radio frequency generator, detector, and reader. It then discusses the importance of using deuterated solvents like CDCl3 in NMR to minimize background signals. The document also explains the two main nuclear relaxation processes in NMR - spin-lattice and spin-spin relaxation. Additional sections cover factors that influence chemical shifts like electronegativity and anisotropic effects. Finally, the document provides examples of the number of NMR signals expected for different compounds based on equivalent and non-equivalent protons.
1. Spin-spin splitting occurs when nonequivalent protons on the same carbon or adjacent carbons interact with each other magnetically. This causes peaks in NMR spectra to split into multiplets.
2. The number of peaks in a multiplet is determined by the "n+1" rule, where n is the number of protons on adjacent carbons. For example, two adjacent protons cause a doublet, three adjacent protons cause a triplet.
3. The intensities of peaks within multiplets follow Pascal's triangle, such as a triplet having peak intensities of 1:2:1. This is because of the different magnetic environments felt by the absorbing proton due to the alignments of adjacent protons.
Mass spectrometry deals with studying charged molecules and fragment ions produced from a sample exposed to ionizing conditions. It provides the relative intensity spectrum based on ions' mass to charge ratio, allowing identification of unknown compounds. The document discusses the basic principles, advantages, disadvantages, instrumentation, applications, and analysis techniques of mass spectrometry.
Calibration - UV VIS Spectrophotometer, HPLC, Gas Chromatograph, IR spectroph...SELINA SRAVANTHI
Calibration of analytical instruments is important to ensure accurate measurements. It involves comparing instruments to more precise reference standards. Calibrating UV-Vis spectrophotometers involves checking wavelength accuracy using holmium filters, absorbance accuracy using potassium dichromate, stray light levels, resolution, and linearity. Calibrating IR spectrometers involves checking wavenumber accuracy using polystyrene, resolution, transmittance levels, linearity, and reproducibility. Calibrating fluorimeters involves setting excitation/emission wavelengths and adjusting the concentration readout using standards. Calibrating HPLCs involves checking flow rate accuracy and gradient performance using solvent mixtures.
The versatile instrument is used to isolate unknown compounds from a HPTLC/TLC plate and transfer them into a mass spectrometer for identification or structure elucidation.
This document discusses various topics related to UV-visible spectroscopy including:
1. Choice of solvents and their effects on UV-visible spectra. Polar solvents can cause red or blue shifts in absorption maxima depending on the solute.
2. Applications of UV-visible spectroscopy like quantitative analysis of single and multiple component samples and qualitative analysis through structural elucidation, detection of functional groups, and identification of compounds.
3. Difference spectroscopy, where the difference in absorbance between two samples is measured to improve selectivity in the presence of interfering absorbers.
Quenching is a process that decreases fluorescence intensity of a substance. It can occur due to various factors like pH, temperature, viscosity, and complex formation. There are different types of quenching, including concentration quenching where intensity decreases with higher concentration, and chemical quenching affected by pH, oxygen, halides, heavy metals, and electron withdrawing groups. Quenching can also be static, where a non-fluorescent complex forms, or collisional from factors increasing collision frequency. Key factors affecting quenching are pH, oxygen, temperature, halides, heavy metals, and electron withdrawing groups.
The document discusses infrared (IR) spectroscopy, which analyzes the interaction of infrared radiation with matter. IR spectroscopy can provide information about a compound's chemical structure and molecular structure by measuring its absorption of IR radiation. It is widely used to analyze organic materials and some inorganic molecules. The document then describes various components of IR instrumentation, including IR radiation sources like the Nernst glower and globar, monochromators that separate wavelengths, sample cells and techniques, and detectors like thermocouples, bolometers, and thermistors that measure the radiation absorbed.
This document discusses various ionization techniques used in mass spectrometry. It begins with an introduction to mass spectrometry and its basic principles. It then describes several ionization sources including gas phase sources like electron impact ionization and chemical ionization, and desorption sources like electrospray ionization, matrix-assisted laser desorption/ionization, and fast atom bombardment. The document proceeds to provide more detailed explanations of specific ionization techniques like electrospray ionization, atmospheric pressure chemical ionization, atmospheric pressure photoionization, matrix-assisted laser desorption ionization, and fast atom bombardment. It concludes with references used in the document.
Nuclear magnetic resonance spectroscopy involves subjecting atomic nuclei to magnetic fields and measuring the electromagnetic radiation absorbed and emitted. Fourier transform NMR provides increased sensitivity by combining multiple free induction decay signals measured in the time domain. A Fourier transform converts these signals to an NMR spectrum in the frequency domain. The Michelson interferometer induces interference of light waves by splitting and recombining beams that traveled different path lengths, allowing observation of interference patterns related to the wavelength of light.
Quadrupole and Time of Flight Mass analysers.Gagangowda58
Description about important mass analysers Quadrupole and TOF: Principle, Construction and Working, Advantages and Disadvantages and their Applications.
1. 1H NMR spectroscopy is a technique used to analyze compounds by detecting hydrogen nuclei in a magnetic field. It provides information about functional groups, number of nuclei, and structure of compounds.
2. The principle involves hydrogen nuclei absorbing radio frequencies matching their Larmor frequency in an applied magnetic field. This absorption is measured to produce an NMR spectrum.
3. Factors like electronegativity, magnetic anisotropy, and spin-spin coupling influence the chemical shifts observed on the NMR spectrum, allowing identification of functional groups and structure elucidation.
PRINCIPLES of FT-NMR & 13C NMR
Fourier Transform
FOURIER TRANSFORM NMR SPECTROSCOPY
THEORY OF FT-NMR
13C NMR SPECTROSCOPY
Principle
Why C13-NMR is required though we have H1-NMR?
CHARACTERISTIC FEATURES OF 13 C NMR
Chemical Shifts
NUCLEAR OVERHAUSER ENHANCEMENT
Short-Comings of 13C-NMR Spectra
Instrumentation IR Spectroscopy: DetectorsVrushali Tambe
This document discusses various types of detectors used in infrared (IR) spectroscopy. It describes the ideal properties of detectors and compares quantum and thermal detectors. Quantum detectors like photoconductors respond to individual photons, while thermal detectors respond to average power. Common thermal detectors include thermocouples, bolometers, thermistors, Golay cells, and pyroelectric detectors. Photoconductors are the main quantum detectors used for IR as other phototransducers require more energy. The document also provides details on the working principles of various thermal detectors and photoconducting transducers.
There are four main techniques used to prepare solid samples for IR spectroscopy: dissolving solids in solution, solid films, mull technique, and pressed pellet technique. The mull technique involves grinding the solid sample with a mulling agent like mineral oil or nujol to form a paste between IR windows. The pressed pellet technique uses potassium bromide to form a compressed pellet, avoiding interference from a mulling agent. Liquids can be analyzed directly in liquid sample cells of appropriate thickness.
Spectrofluorimetry is a technique that measures fluorescence emitted from molecules. It involves exciting molecules with UV or visible light which causes electrons to transition to an excited state. The molecule then relaxes and emits light of a longer wavelength. Factors like concentration, quantum yield, path length, pH, temperature and presence of quenchers affect the intensity of fluorescence. Spectrofluorimeters are used to collect excitation and emission spectra of molecules to identify them.
This document discusses nepheloturbidometry, which uses light scattering measurements to determine the concentration of suspended particles in liquids. It can be used for both low concentrations (nephelometry) and high concentrations (turbidometry) by measuring either scattered light or transmitted light. A nepheloturbidimeter has detectors to measure both scattered light at 90 degrees and transmitted light at 180 degrees, allowing it to analyze suspensions of unknown concentration. Factors like particle properties, light source, sample cells, and detectors can affect light scattering measurements. Nepheloturbidimetry has various applications like analyzing water clarity, determining carbon dioxide, and quantifying ions at low levels.
This document provides calibration procedures for various instruments used in pharmaceutical analysis. It describes calibrating a UV-Vis spectrophotometer using holmium perchlorate and potassium dichromate primary standards to control wavelength and absorbance. It also provides procedures to calibrate using potassium chloride and toluene solutions. Regular calibration is important to ensure instruments produce accurate results, and should be performed when time periods elapse, operating hours change, a new instrument is used, or observations seem questionable.
This document provides an overview of NMR spectroscopy. It begins by explaining the fundamental principles, including that NMR spectroscopy detects the absorption of radio waves by atomic nuclei placed in a magnetic field. It then discusses various aspects of interpreting NMR spectra such as chemical shifts, spin-spin coupling and integrals. The document also covers NMR techniques including Fourier transformation, 2D NMR, and relaxation processes. In summary, the document serves as an introduction to NMR spectroscopy and the principles behind analyzing NMR spectral data.
Flame photometry is a technique used to analyze metals in solutions. It works by measuring the intensity of light emitted from a flame when a metal salt solution is introduced. Each metal emits a characteristic wavelength of light that can be used to identify the metal qualitatively, and the intensity is proportional to the concentration quantitatively. The sample is nebulized and introduced into a flame, where it is vaporized, dissociated into atoms, and the atoms are excited by the flame's thermal energy to emit photons. Interferences can occur from overlapping emission lines, ionization, or chemical reactions. The instrumentation includes components for sample delivery, a burner to produce the flame, mirrors to direct the light, and a detector to measure
Nuclear Magnetic Double Resonance (Decoupling).pptxRushikeshTidake
This document discusses nuclear magnetic double resonance (decoupling) in NMR spectroscopy. It explains that decoupling involves irradiating a proton to prevent coupling with neighboring protons, simplifying complex spectra. Decoupling causes multiplets to collapse into doublets or singlets, making spectra easier to interpret. It provides an example using ethanol, noting how decoupling removes signals by exchanging protons for deuterium. The document also discusses how decoupling averages spins to zero to remove spin-spin interactions and simplify coupled signals.
Nuclear magnetic resonance (NMR) spectroscopy uses powerful magnets and radiofrequency energy to characterize organic molecules. NMR spectrometers consist of a magnet to align nuclear spins, a radiofrequency source to excite spins, and a detector to measure the energy absorbed. The main components are the magnet, probe, and electronics for excitation and detection. NMR provides information about carbon-hydrogen frameworks by measuring the energy required for nuclei to change spin orientation in the magnetic field.
Nmr nuclear magnetic resonance spectroscopyJoel Cornelio
Basics of NMR. Suitable for UG and PG courses.
Includes principle, instrumentation, solvents. chemical shift and factors affecting it. Some problems. resolving agents, coupling constant and much more
The versatile instrument is used to isolate unknown compounds from a HPTLC/TLC plate and transfer them into a mass spectrometer for identification or structure elucidation.
This document discusses various topics related to UV-visible spectroscopy including:
1. Choice of solvents and their effects on UV-visible spectra. Polar solvents can cause red or blue shifts in absorption maxima depending on the solute.
2. Applications of UV-visible spectroscopy like quantitative analysis of single and multiple component samples and qualitative analysis through structural elucidation, detection of functional groups, and identification of compounds.
3. Difference spectroscopy, where the difference in absorbance between two samples is measured to improve selectivity in the presence of interfering absorbers.
Quenching is a process that decreases fluorescence intensity of a substance. It can occur due to various factors like pH, temperature, viscosity, and complex formation. There are different types of quenching, including concentration quenching where intensity decreases with higher concentration, and chemical quenching affected by pH, oxygen, halides, heavy metals, and electron withdrawing groups. Quenching can also be static, where a non-fluorescent complex forms, or collisional from factors increasing collision frequency. Key factors affecting quenching are pH, oxygen, temperature, halides, heavy metals, and electron withdrawing groups.
The document discusses infrared (IR) spectroscopy, which analyzes the interaction of infrared radiation with matter. IR spectroscopy can provide information about a compound's chemical structure and molecular structure by measuring its absorption of IR radiation. It is widely used to analyze organic materials and some inorganic molecules. The document then describes various components of IR instrumentation, including IR radiation sources like the Nernst glower and globar, monochromators that separate wavelengths, sample cells and techniques, and detectors like thermocouples, bolometers, and thermistors that measure the radiation absorbed.
This document discusses various ionization techniques used in mass spectrometry. It begins with an introduction to mass spectrometry and its basic principles. It then describes several ionization sources including gas phase sources like electron impact ionization and chemical ionization, and desorption sources like electrospray ionization, matrix-assisted laser desorption/ionization, and fast atom bombardment. The document proceeds to provide more detailed explanations of specific ionization techniques like electrospray ionization, atmospheric pressure chemical ionization, atmospheric pressure photoionization, matrix-assisted laser desorption ionization, and fast atom bombardment. It concludes with references used in the document.
Nuclear magnetic resonance spectroscopy involves subjecting atomic nuclei to magnetic fields and measuring the electromagnetic radiation absorbed and emitted. Fourier transform NMR provides increased sensitivity by combining multiple free induction decay signals measured in the time domain. A Fourier transform converts these signals to an NMR spectrum in the frequency domain. The Michelson interferometer induces interference of light waves by splitting and recombining beams that traveled different path lengths, allowing observation of interference patterns related to the wavelength of light.
Quadrupole and Time of Flight Mass analysers.Gagangowda58
Description about important mass analysers Quadrupole and TOF: Principle, Construction and Working, Advantages and Disadvantages and their Applications.
1. 1H NMR spectroscopy is a technique used to analyze compounds by detecting hydrogen nuclei in a magnetic field. It provides information about functional groups, number of nuclei, and structure of compounds.
2. The principle involves hydrogen nuclei absorbing radio frequencies matching their Larmor frequency in an applied magnetic field. This absorption is measured to produce an NMR spectrum.
3. Factors like electronegativity, magnetic anisotropy, and spin-spin coupling influence the chemical shifts observed on the NMR spectrum, allowing identification of functional groups and structure elucidation.
PRINCIPLES of FT-NMR & 13C NMR
Fourier Transform
FOURIER TRANSFORM NMR SPECTROSCOPY
THEORY OF FT-NMR
13C NMR SPECTROSCOPY
Principle
Why C13-NMR is required though we have H1-NMR?
CHARACTERISTIC FEATURES OF 13 C NMR
Chemical Shifts
NUCLEAR OVERHAUSER ENHANCEMENT
Short-Comings of 13C-NMR Spectra
Instrumentation IR Spectroscopy: DetectorsVrushali Tambe
This document discusses various types of detectors used in infrared (IR) spectroscopy. It describes the ideal properties of detectors and compares quantum and thermal detectors. Quantum detectors like photoconductors respond to individual photons, while thermal detectors respond to average power. Common thermal detectors include thermocouples, bolometers, thermistors, Golay cells, and pyroelectric detectors. Photoconductors are the main quantum detectors used for IR as other phototransducers require more energy. The document also provides details on the working principles of various thermal detectors and photoconducting transducers.
There are four main techniques used to prepare solid samples for IR spectroscopy: dissolving solids in solution, solid films, mull technique, and pressed pellet technique. The mull technique involves grinding the solid sample with a mulling agent like mineral oil or nujol to form a paste between IR windows. The pressed pellet technique uses potassium bromide to form a compressed pellet, avoiding interference from a mulling agent. Liquids can be analyzed directly in liquid sample cells of appropriate thickness.
Spectrofluorimetry is a technique that measures fluorescence emitted from molecules. It involves exciting molecules with UV or visible light which causes electrons to transition to an excited state. The molecule then relaxes and emits light of a longer wavelength. Factors like concentration, quantum yield, path length, pH, temperature and presence of quenchers affect the intensity of fluorescence. Spectrofluorimeters are used to collect excitation and emission spectra of molecules to identify them.
This document discusses nepheloturbidometry, which uses light scattering measurements to determine the concentration of suspended particles in liquids. It can be used for both low concentrations (nephelometry) and high concentrations (turbidometry) by measuring either scattered light or transmitted light. A nepheloturbidimeter has detectors to measure both scattered light at 90 degrees and transmitted light at 180 degrees, allowing it to analyze suspensions of unknown concentration. Factors like particle properties, light source, sample cells, and detectors can affect light scattering measurements. Nepheloturbidimetry has various applications like analyzing water clarity, determining carbon dioxide, and quantifying ions at low levels.
This document provides calibration procedures for various instruments used in pharmaceutical analysis. It describes calibrating a UV-Vis spectrophotometer using holmium perchlorate and potassium dichromate primary standards to control wavelength and absorbance. It also provides procedures to calibrate using potassium chloride and toluene solutions. Regular calibration is important to ensure instruments produce accurate results, and should be performed when time periods elapse, operating hours change, a new instrument is used, or observations seem questionable.
This document provides an overview of NMR spectroscopy. It begins by explaining the fundamental principles, including that NMR spectroscopy detects the absorption of radio waves by atomic nuclei placed in a magnetic field. It then discusses various aspects of interpreting NMR spectra such as chemical shifts, spin-spin coupling and integrals. The document also covers NMR techniques including Fourier transformation, 2D NMR, and relaxation processes. In summary, the document serves as an introduction to NMR spectroscopy and the principles behind analyzing NMR spectral data.
Flame photometry is a technique used to analyze metals in solutions. It works by measuring the intensity of light emitted from a flame when a metal salt solution is introduced. Each metal emits a characteristic wavelength of light that can be used to identify the metal qualitatively, and the intensity is proportional to the concentration quantitatively. The sample is nebulized and introduced into a flame, where it is vaporized, dissociated into atoms, and the atoms are excited by the flame's thermal energy to emit photons. Interferences can occur from overlapping emission lines, ionization, or chemical reactions. The instrumentation includes components for sample delivery, a burner to produce the flame, mirrors to direct the light, and a detector to measure
Nuclear Magnetic Double Resonance (Decoupling).pptxRushikeshTidake
This document discusses nuclear magnetic double resonance (decoupling) in NMR spectroscopy. It explains that decoupling involves irradiating a proton to prevent coupling with neighboring protons, simplifying complex spectra. Decoupling causes multiplets to collapse into doublets or singlets, making spectra easier to interpret. It provides an example using ethanol, noting how decoupling removes signals by exchanging protons for deuterium. The document also discusses how decoupling averages spins to zero to remove spin-spin interactions and simplify coupled signals.
Nuclear magnetic resonance (NMR) spectroscopy uses powerful magnets and radiofrequency energy to characterize organic molecules. NMR spectrometers consist of a magnet to align nuclear spins, a radiofrequency source to excite spins, and a detector to measure the energy absorbed. The main components are the magnet, probe, and electronics for excitation and detection. NMR provides information about carbon-hydrogen frameworks by measuring the energy required for nuclei to change spin orientation in the magnetic field.
Nmr nuclear magnetic resonance spectroscopyJoel Cornelio
Basics of NMR. Suitable for UG and PG courses.
Includes principle, instrumentation, solvents. chemical shift and factors affecting it. Some problems. resolving agents, coupling constant and much more
FT-NMR uses Fourier transforms to convert time domain signals from nuclear magnetic resonance into frequency domain spectra. The sample is placed in a strong magnet and exposed to pulses of radio frequency radiation, producing a free induction decay signal that is recorded over time. This time domain signal is then digitized and analyzed using a Fourier transform program on a computer to produce the frequency domain NMR spectrum. FT-NMR provides higher sensitivity than continuous wave NMR, allowing analysis of smaller sample sizes.
The document discusses two-dimensional nuclear magnetic resonance spectroscopy (2D NMR). 2D NMR provides more structural information about molecules than 1D NMR. There are several types of 2D NMR experiments that provide different information, including COSY, TOCSY, HSQC, and NOESY. These experiments establish correlations between nuclei that are directly bonded or spatially close. 2D NMR is useful for determining molecular structures, especially of complex biomolecules like proteins.
Introduction to analytical instrumentation.Analysys
This document provides an overview of analytical chemistry techniques. It discusses the evolution of analytical instrumentation from 1900s to present day, allowing for detection of smaller and smaller quantities. Key separation techniques like chromatography (HPLC, GC) and planar chromatography (TLC) are explained. The document highlights pioneers in the field and applications in industries like pharmaceutical, biotech, environmental testing. It provides examples of current instrumentation and trends toward portable, automated, and higher resolution analysis.
This document outlines a PowerPoint presentation on nuclear magnetic resonance (NMR) spectroscopy. It covers the fundamentals of NMR including spin-spin coupling, instrumentation, solvents, chemical shifts, and 2D NMR techniques. Applications discussed include structure elucidation of organic compounds and biomolecules, as well as clinical uses such as MRI. Specific NMR experiments summarized are COSY, NOESY, and HETCOR.
Nuclear magnetic resonance spectroscopy (NMR) involves subjecting a sample to a strong, stationary magnetic field and a second varying magnetic field at radio frequencies. This causes the nuclei in the sample to absorb energy and alter their spin state. The energy absorbed and precessional frequency of nuclei depends on factors like the magnetic field strength and properties of individual nuclei like their spin and magnetic moment. NMR provides information on the chemical environment and bonding of atoms in a molecule through analysis of spectra.
The document provides a summary of the history and development of Nuclear Magnetic Resonance (NMR) Spectroscopy. Some key points include:
1. NMR was first predicted in 1937 and first observed on bulk samples in 1946. Important early developments included 2D NMR in 1975 and NMR metabolomics in 1984.
2. NMR utilizes the magnetic properties of certain atomic nuclei to determine structural information about molecules. It provides information about the number and type of hydrogen atoms, as well as their electronic environment.
3. For a nucleus to be observable by NMR, it must have a non-zero spin quantum number and magnetic moment, and be spherical in shape. Common nuclei studied include 1H, 13C, 19
This document provides an introduction to NMR spectroscopy for identifying organic compounds. It discusses key concepts like:
1. NMR spectroscopy uses radiofrequency radiation to excite nuclei like 1H and 13C in a strong magnetic field, revealing information about molecular structure.
2. Features of a 1H NMR spectrum like number of signals, chemical shifts, signal areas, and splitting patterns provide clues about a molecule's structure like number/type of protons and connectivity.
3. Chemical shifts are measured in parts per million (ppm) relative to a reference and indicate magnetic environments, with tables correlating shifts to structural features.
It is spectroscopy technique to determine number of hydrogen atoms present in the molecules and atoms.It is useful method for separation of molecules and compounds from mixtures components highly recommended in pharmaceutical and chemical engineering fields.
The document provides information about nuclear magnetic resonance (NMR) spectroscopy. It discusses:
1) A brief history of NMR spectroscopy from its discovery in 1945 to its application in organic chemistry structure determination and receipt of Nobel Prizes.
2) How NMR spectroscopy works by placing a sample in a strong magnetic field and detecting radio signals produced by excitation of atomic nuclei.
3) How NMR spectra provide information about molecular structure by revealing the number of magnetically distinct atoms and details about atomic environments.
4) Factors that affect chemical shifts observed in NMR spectra, including electronegativity, hybridization, and magnetic anisotropy effects.
This document provides information about Nuclear Magnetic Resonance (NMR) spectroscopy and Electron Paramagnetic Resonance (EPR) spectroscopy. It discusses the basic principles and instrumentation of NMR and EPR. NMR spectroscopy works by applying a magnetic field to atomic nuclei and measuring the electromagnetic radiation absorbed and emitted. It is useful for structural analysis of molecules. EPR spectroscopy similarly applies a magnetic field to unpaired electrons and measures electromagnetic absorption. Both techniques provide information about molecular structure and interactions. The document outlines applications of NMR and EPR spectroscopy including molecular structure determination, protein structure analysis, medical imaging, and analyzing irradiated and radical-containing foods and biological samples.
Nuclear magnetic resonance by ayush kumawatAyush Kumawat
This document provides an overview of a presentation on Nuclear Magnetic Resonance (NMR) Spectroscopy. The presentation covers the history of NMR, principles, instrumentation, techniques and applications of NMR spectroscopy. It discusses key topics such as NMR spectra, spin quantum number, chemical shift, spin-spin coupling and solvents used. The presentation was given by Ayush Kumawat, a 7th semester B.Pharma student under the guidance of Dr. Priyadarshini Kamble at BHUPAL NOBEL’S COLLEGE OF PHARMACY in Udaipur.
This document provides an overview of proton NMR spectroscopy. It begins with definitions of light and the electromagnetic spectrum. It then discusses spectroscopy in general and introduces NMR, focusing on proton NMR. The key concepts of proton NMR covered include its principle, instrumentation, chemical shifts, spin-spin splitting, deuterium exchange, and the n+1 rule. Applications discussed include distinguishing isomers, determining molecular weight, and studying tautomeric mixtures. Clinical, agricultural, and biological applications are also mentioned.
The document provides information on nuclear magnetic resonance (NMR) spectroscopy. It discusses key concepts such as nuclear spin, magnetic moments, energy levels of nuclei in magnetic fields, and spin-spin coupling. Nuclear spin gives rise to quantized magnetic moments and angular momentum. In an external magnetic field, these magnetic moments can align parallel or anti-parallel, splitting the energy levels. The energy difference between levels depends on the field strength and nucleus. NMR spectroscopy detects the absorption frequencies of nuclei as they transition between energy levels when irradiated with radio waves. Chemical shifts arise from electron shielding effects, allowing NMR to distinguish between similar nuclei. Spin-spin coupling further splits peaks into multiplets, providing detailed information about molecular structure.
The document provides information about Nuclear Magnetic Resonance (NMR) Spectroscopy, including:
1. A brief history of NMR and important contributors such as Felix Bloch, Edward Purcell, Kurt Wuthrich, and Richard Ernst.
2. Applications of NMR including chemical structure analysis, material characterization, study of dynamic processes, and biomolecular structure determination.
3. Explanations of key NMR concepts such as nuclear spin, precession, resonance frequency, and chemical shift.
This document summarizes a student project on magnetic resonance imaging (MRI). It provides background on the discovery of MRI, how MRI works by aligning hydrogen protons in tissue with a magnetic field and radio waves. It also describes how MRI generates tomographic images of thin slices through the body and provides several medical applications and diagnostic images.
1) NMR spectroscopy allows determination of molecular structure by measuring frequencies at which atomic nuclei absorb radio waves in a strong magnetic field. These frequencies depend on the nucleus and its chemical environment.
2) In an NMR experiment, a sample is placed in a strong magnetic field which causes atomic nuclei to align with the field. Radio waves are then applied and nuclei absorb at characteristic frequencies.
3) The frequencies observed in the NMR spectrum provide information about a molecule's structure by indicating chemically distinct nuclear environments.
This document provides an overview of nuclear magnetic resonance (NMR) spectroscopy. It discusses key concepts such as Larmor precession, spin-spin and spin-lattice relaxation, relative line intensities, and the quantum mechanical treatment of the AB spin system. The document is a seminar presentation that covers the basic principles and applications of NMR spectroscopy for structure determination of organic and inorganic compounds.
1. Nuclear magnetic resonance spectroscopy (NMR) involves placing a sample in a strong magnetic field and observing the absorption of radio waves by atomic nuclei within the sample.
2. NMR spectroscopy has been developed since the 1930s. Early developments included accurate measurements of nuclear magnetic moments in 1938 and the first demonstration of NMR for condensed matter in 1946.
3. Modern NMR instruments contain components like a strong magnet, radio transmitters and receivers, and recorders to detect NMR signals from nuclei like 1H and 13C and provide information about molecular structure.
1. Nuclear magnetic resonance (NMR) spectroscopy measures the absorption of radio waves by atomic nuclei placed in a magnetic field. It can provide information about a molecule's structure.
2. NMR works because some atomic nuclei have spin and behave like tiny magnets. When a magnetic field is applied, they align with or against the field. Radio waves can excite the nuclei to a higher energy state.
3. The energy required for this transition, and thus the radio frequency needed, depends on the magnetic field strength and properties of the specific nucleus such as its gyromagnetic ratio. NMR spectra reveal the unique environments of different nuclei in a molecule.
CHEMICAL SHIFT AND ITS FACTOR EFFECTS, COUPLING CONSTANT, FIRST ORDER TO NON FIRST ORDER, SPIN SYSTEMS, CHEMICAL EQUIVALENCE AND NON EQUIVALENCE, TIRUMALA SANTHOSHKUMAR S
MRI relies on the spin properties of hydrogen nuclei in the body. When placed in a strong magnetic field, hydrogen nuclei align their magnetic moments either parallel or anti-parallel to the field. There are slightly more nuclei aligned parallel, producing a net magnetic vector. The nuclei precess around the magnetic field at their Larmor frequency, which is proportional to field strength. Radio waves applied at the Larmor frequency can manipulate the nuclei's alignment.
NMR spectroscopy uses radio waves to induce transitions between magnetic energy levels of nuclei in a molecule. When placed in an external magnetic field, nuclei with spin precess at the Larmor frequency, which is proportional to the field strength. Absorption of radio waves at the Larmor frequency causes spin flipping between energy levels. The NMR spectrum provides information on chemical environments and molecular structure from chemical shifts, peak multiplicities, integrals, and coupling constants.
The document provides an overview of the theory of nuclear magnetic resonance (NMR) spectroscopy. It discusses how nuclei with spin absorb electromagnetic radiation when placed in a magnetic field, creating distinct energy levels. When radio waves are applied at the resonance frequency, transitions between spin states occur, producing signals in the NMR spectrum. Chemical shifts arise from electrons shielding or deshielding nuclei from the magnetic field in different ways. Neighboring protons cause splitting of peaks according to spin-spin coupling rules.
Similar to 3. b.pharm nuclearmagneticresonance jntu pharmacy (20)
This document discusses Karl Fischer titration methods for determining water content. It covers the KF reaction, volumetric and coulometric titration techniques, endpoint indication, drift correction, parameters, and KF instrumentation. Volumetric titration uses an iodine titrant while coulometric generates iodine via electrolysis. Both methods indicate the endpoint potentiometrically and use drift as a secondary check. Parameters like dynamics, stop criteria, and currents must be optimized. Common KF titration instruments include the Titrino, Titrando, Coulometer, and oven systems.
Redox titrations involve adjusting the oxidation state of the analyte using an auxiliary oxidizing or reducing agent so that it can be titrated. Common reagents used in redox titrations include potassium permanganate, sodium thiosulfate, cerium sulfate, and potassium dichromate. Redox titrations are used to determine various analytes like ascorbic acid, hydrogen peroxide, iron, and calcium compounds. The document discusses the principles and procedures of important redox titrations like permanganometry, iodimetry, cerimetry, and dichrometry. It also describes the determination of water using the Karl Fischer reagent and reaction.
Polarography is a type of voltammetry where the working electrode is a dropping mercury electrode (DME). A polarographic cell contains a solution of interest, a reference electrode like calomel, a small DME indicator electrode, and an auxiliary electrode. Mercury is dropped from the DME at a stable rate, and current versus potential is recorded as voltage is applied gradually. The DME allows for analysis of very small sample volumes due to its narrow capillary. However, polarography is limited to potentials between +0.4 and -2 V, and the small capillary can become blocked. The diffusion current in polarography depends on factors like analyte concentration, diffusion coefficient, mercury drop flow rate, and drop lifetime
This document discusses complexation and chelation in analytical chemistry. It provides information on:
1) How complexes are formed through coordination bonds between metal ions and ligands. Chelating agents form stable chelate complexes by donating multiple electron pairs.
2) EDTA is a hexadentate ligand that forms very stable chelate complexes due to the chelate effect. It is commonly used in complexometric titrations.
3) The stability and formation of metal-EDTA complexes depends on factors like the formation constant, concentrations of reactants, and solution pH. Titration curves have a sharper break at higher pH values.
The document discusses infrared spectroscopy and its importance in drug analysis. It covers the following key points in 3 sentences:
1) Infrared spectroscopy analyzes the interaction of electromagnetic radiation with matter and is useful for identifying functional groups and determining drug structure. 2) The technique is based on measuring the vibrational and rotational energies of molecules which causes absorption of specific infrared wavelengths. 3) Infrared spectroscopy has various applications in pharmacy, biotechnology and genetic engineering by allowing identification, quantification and study of interactions of drug molecules.
This document discusses non-aqueous titration, which involves titrating weakly acidic or basic substances using non-aqueous solvents to obtain a sharp endpoint. It describes the different types of non-aqueous solvents that can be used, including aprotic, protophilic, protogenic, and amphiprotic solvents. The document also discusses how solvent properties affect acidity and outlines methods for titrating weak acids and bases via potentiometric or indicator methods. Key indicators and solvents used for titrating each are provided.
This document discusses nephelometry and turbidimetry techniques for measuring light scattering in solutions. Nephelometry measures scattered light at a 90 degree angle to the incident light beam, while turbidimetry measures transmitted light at 180 degrees. Both techniques can be used to determine particle concentrations but nephelometry is more accurate for low concentrations. Common applications include analyzing water quality and determining inorganic substances or biochemicals. Key factors affecting the measurements are particle concentration, size, shape, and wavelength of light used.
This document discusses several thermal analysis techniques including differential thermal analysis (DTA). It explains that DTA involves heating a sample and inert reference material simultaneously and measuring any temperature difference, which can indicate physical or chemical changes in the sample. The document provides details on DTA instrumentation, the factors that can affect DTA results, and applications such as material identification and purity assessment by comparing DTA curves.
This document discusses validation in the pharmaceutical industry. It begins by defining validation according to the FDA as establishing evidence that a process will consistently produce a product meeting predetermined specifications. It then covers the role of the FDA in setting validation guidelines. The rest of the document discusses validating equipment and processes. Equipment validation involves installation, operational, and performance qualification. Process validation demonstrates a process can repeatedly produce the desired product. The document stresses the importance of validation in ensuring quality, functionality, and performance of manufacturing processes and equipment.
This document discusses Good Laboratory Practice (GLP), which are quality standards that regulate the conduct of non-clinical laboratory studies. It was created by the FDA in 1978 after investigations found fraudulent activities and poor practices in toxicology labs. GLP provides principles for planning, conducting, monitoring, recording, reporting and archiving laboratory studies according to standard operating procedures to ensure the quality and integrity of data. Non-compliance with GLP can result in the disqualification of a testing facility, rejection of study data, and civil or criminal penalties.
X-ray diffraction is a technique used to analyze the crystal structure of materials. It works by firing X-rays at a crystalline sample and measuring the angles and intensities of the diffracted X-rays. This diffraction pattern acts as a "fingerprint" identifying the sample. Bragg's law describes how the diffraction pattern relates to the spacing of planes in the crystal lattice. XRD is used to determine properties like lattice parameters, grain size, strain, phase composition and crystal orientation. It has applications in fields like materials science, pharmaceuticals, and forensics.
Nuclear magnetic resonance (NMR) spectroscopy involves analyzing the magnetic properties of atomic nuclei, specifically the spin state of protons. NMR spectra provide information about a compound's structure by indicating the number of different types of protons, the intensity of peaks corresponding to proton count, and peak splitting patterns revealing nearby protons. Chemical shifts along the δ scale indicate the electron density around protons. Factors like electronegativity, hybridization, and hydrogen bonding influence chemical shifts. Coupling constants describe the distance between peaks in multiplets from spin-spin splitting. NMR spectroscopy is useful for analyzing functional groups in compounds like alkanes, alkenes, aromatics, alcohols, amines, and more.
This document provides an overview of mass spectroscopy. It begins with a brief introduction and then discusses the basic principles, theory, instrumentation, ion formation, and fragmentation processes involved in mass spectroscopy. The key points covered include:
- Mass spectroscopy involves ionizing molecules and separating the resulting ions based on their mass-to-charge ratio.
- Ions are formed by bombarding molecules with electrons, which causes ionization through electron removal. The ions are then accelerated, deflected according to their mass, and detected.
- Fragmentation of molecular ions can occur, producing fragment ions of lower mass. The molecular ion peak indicates the molecular weight.
- Instrumentation includes an ionization source, acceleration/def
The document discusses the legislative framework and process for obtaining patents in India. It outlines the key government bodies that administer patents, as well as the various acts and rules that govern patents. It then describes the stages involved in filing a patent application, including formalities check, publication, examination, opposition proceedings, and renewal fees. The objectives of patent law are also summarized as providing a statutory right to inventors for a period of time to commercially exploit their invention, while also encouraging innovation and ensuring inventions eventually enter the public domain.
1. The document discusses various topics related to intellectual property rights (IPR) such as the meaning of IPR, types of IPR including patents, trademarks, copyright, and infringement.
2. It provides information on organizations like WIPO that promote IPR, examples of famous inventors, and the importance and purpose of having legal protection for IP.
3. The key types of IP covered are patents, trademarks, copyright, industrial designs, geographical indications, and trade secrets along with the laws governing them in India.
The document provides guidelines on the data required to be submitted for conducting clinical trials or importing/manufacturing new drugs in India. It includes details on chemical/pharmaceutical information, animal pharmacology/toxicology studies, human clinical trial phases, special studies like bioavailability/bioequivalence studies, regulatory status in other countries, prescribing information, and samples/testing protocols. Appendices provide more details on topics like clinical study report format/structure, animal toxicology parameters, and male fertility studies.
A sterility test assesses whether a pharmaceutical product is free from microorganisms. It involves incubating samples of the product in nutrient media. There are three main methods for conducting sterility tests: direct inoculation into media, membrane filtration, and adding concentrated media to products in their original containers. Two common media used are fluid thioglycollate medium and soybean-casein digest medium. Controls and appropriate sampling methods are necessary to accurately determine if a batch meets sterility requirements.
Process validation involves three key stages:
1) Process design to define the commercial manufacturing process based on development and scale-up.
2) Process qualification to evaluate the design and determine if reproducible commercial manufacturing is possible.
3) Continued process verification to ensure the process remains in control during routine production through monitoring and adjustment.
This document discusses quality control tests for various pharmaceutical packaging materials including glass containers, closures, collapsible tubes, metallic tins, strips, blisters, and paper/board. It describes tests to evaluate the chemical resistance, hydrolytic resistance, arsenic content, thermal shock resistance, internal bursting pressure, and leakage of glass containers. Similar tests are described for evaluating the sterility, fragmentation, self-sealability, pH, light absorption, and residue of closures. Tests for collapsible tubes include leakage testing, collapsibility testing, and lacquer curing/compatibility. Dimensional measurements and cleanliness checks are discussed for metallic tins. Vacuum testing is described for quality control of strips and
This document provides an overview of the history and development of Good Manufacturing Practices (GMP) regulations. It discusses key events that led to the establishment of GMP standards, including unsafe drug production in the early 1900s and the Thalidomide tragedy in the 1960s. The document then outlines the main GMP guidelines covering areas like personnel, facilities, equipment, sanitation, documentation, raw materials, quality assurance, and more. It traces the timeline of major GMP-related acts and amendments between 1902-1980 to strengthen drug and medical device manufacturing standards.
Gender and Mental Health - Counselling and Family Therapy Applications and In...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Philippine Edukasyong Pantahanan at Pangkabuhayan (EPP) CurriculumMJDuyan
(𝐓𝐋𝐄 𝟏𝟎𝟎) (𝐋𝐞𝐬𝐬𝐨𝐧 𝟏)-𝐏𝐫𝐞𝐥𝐢𝐦𝐬
𝐃𝐢𝐬𝐜𝐮𝐬𝐬 𝐭𝐡𝐞 𝐄𝐏𝐏 𝐂𝐮𝐫𝐫𝐢𝐜𝐮𝐥𝐮𝐦 𝐢𝐧 𝐭𝐡𝐞 𝐏𝐡𝐢𝐥𝐢𝐩𝐩𝐢𝐧𝐞𝐬:
- Understand the goals and objectives of the Edukasyong Pantahanan at Pangkabuhayan (EPP) curriculum, recognizing its importance in fostering practical life skills and values among students. Students will also be able to identify the key components and subjects covered, such as agriculture, home economics, industrial arts, and information and communication technology.
𝐄𝐱𝐩𝐥𝐚𝐢𝐧 𝐭𝐡𝐞 𝐍𝐚𝐭𝐮𝐫𝐞 𝐚𝐧𝐝 𝐒𝐜𝐨𝐩𝐞 𝐨𝐟 𝐚𝐧 𝐄𝐧𝐭𝐫𝐞𝐩𝐫𝐞𝐧𝐞𝐮𝐫:
-Define entrepreneurship, distinguishing it from general business activities by emphasizing its focus on innovation, risk-taking, and value creation. Students will describe the characteristics and traits of successful entrepreneurs, including their roles and responsibilities, and discuss the broader economic and social impacts of entrepreneurial activities on both local and global scales.
Chapter wise All Notes of First year Basic Civil Engineering.pptxDenish Jangid
Chapter wise All Notes of First year Basic Civil Engineering
Syllabus
Chapter-1
Introduction to objective, scope and outcome the subject
Chapter 2
Introduction: Scope and Specialization of Civil Engineering, Role of civil Engineer in Society, Impact of infrastructural development on economy of country.
Chapter 3
Surveying: Object Principles & Types of Surveying; Site Plans, Plans & Maps; Scales & Unit of different Measurements.
Linear Measurements: Instruments used. Linear Measurement by Tape, Ranging out Survey Lines and overcoming Obstructions; Measurements on sloping ground; Tape corrections, conventional symbols. Angular Measurements: Instruments used; Introduction to Compass Surveying, Bearings and Longitude & Latitude of a Line, Introduction to total station.
Levelling: Instrument used Object of levelling, Methods of levelling in brief, and Contour maps.
Chapter 4
Buildings: Selection of site for Buildings, Layout of Building Plan, Types of buildings, Plinth area, carpet area, floor space index, Introduction to building byelaws, concept of sun light & ventilation. Components of Buildings & their functions, Basic concept of R.C.C., Introduction to types of foundation
Chapter 5
Transportation: Introduction to Transportation Engineering; Traffic and Road Safety: Types and Characteristics of Various Modes of Transportation; Various Road Traffic Signs, Causes of Accidents and Road Safety Measures.
Chapter 6
Environmental Engineering: Environmental Pollution, Environmental Acts and Regulations, Functional Concepts of Ecology, Basics of Species, Biodiversity, Ecosystem, Hydrological Cycle; Chemical Cycles: Carbon, Nitrogen & Phosphorus; Energy Flow in Ecosystems.
Water Pollution: Water Quality standards, Introduction to Treatment & Disposal of Waste Water. Reuse and Saving of Water, Rain Water Harvesting. Solid Waste Management: Classification of Solid Waste, Collection, Transportation and Disposal of Solid. Recycling of Solid Waste: Energy Recovery, Sanitary Landfill, On-Site Sanitation. Air & Noise Pollution: Primary and Secondary air pollutants, Harmful effects of Air Pollution, Control of Air Pollution. . Noise Pollution Harmful Effects of noise pollution, control of noise pollution, Global warming & Climate Change, Ozone depletion, Greenhouse effect
Text Books:
1. Palancharmy, Basic Civil Engineering, McGraw Hill publishers.
2. Satheesh Gopi, Basic Civil Engineering, Pearson Publishers.
3. Ketki Rangwala Dalal, Essentials of Civil Engineering, Charotar Publishing House.
4. BCP, Surveying volume 1
This document provides an overview of wound healing, its functions, stages, mechanisms, factors affecting it, and complications.
A wound is a break in the integrity of the skin or tissues, which may be associated with disruption of the structure and function.
Healing is the body’s response to injury in an attempt to restore normal structure and functions.
Healing can occur in two ways: Regeneration and Repair
There are 4 phases of wound healing: hemostasis, inflammation, proliferation, and remodeling. This document also describes the mechanism of wound healing. Factors that affect healing include infection, uncontrolled diabetes, poor nutrition, age, anemia, the presence of foreign bodies, etc.
Complications of wound healing like infection, hyperpigmentation of scar, contractures, and keloid formation.
Communicating effectively and consistently with students can help them feel at ease during their learning experience and provide the instructor with a communication trail to track the course's progress. This workshop will take you through constructing an engaging course container to facilitate effective communication.
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
1. 1
Nuclear Magnetic Resonance Spectroscopy
BY
Dr. Suman Pattanayak
Associate Professor
Department of Pharma Analysis & QA.
Vijaya Institute of Pharmaceutical Sciences for Women
IV B. Pharm/ I Sem
Pharmaceutical Analysis
3. Introduction
Nuclear spin and magnetic movement
Theory and principle
Applied field and precession
Precessional frequency
Width of absorption line in NMR
Shielding and Deshielding
Reference standard
February 28, 2016 3M.M.C.P.
CONTENTS
4. Chemical shift
Factor affecting chemical shift
Interpretation of PMR
Instrumentation of NMR
Splitting of the signals
Spin-spin coupling
Intensities of Multiplet Peaks
Spin Decoupling
February 28, 2016 4M.M.C.P.
5. NMR spectroscopy is different from the interaction of
electromagnetic radiation with matter.
In this spectroscopy the sample is subjected simultaneously with
two magnetic field, One is a stationary and another is varying at
same radio frequency.
The particular combination of these two field energy is absorbed
by sample and signal is obtained when electromagnetic field is
provided to the nucleus of sample. The nucleus start to spin
around the nuclear axies and generate an another magnetic field.
And particular combination of this two field the energy is
absorbed by nucleus this technique is called as a NMR
spectroscopy.
February 28, 2016 5M.M.C.P.
INTRODUCTION
6. This transition of nucleus occurs in radio frequency region. The
radio waves are considered for lowest energy and this energy is
just sufficient to affect the nuclear spin of the atom in a molecule.
Hence, this is a most fundamental part of NMR spectroscopy.
In general, the study of radio frequency radiation by nuclei is
called nuclear magnetic resonance.
The method of NMR was first developed by E.M. Purcell and
Felix Bloch (1946).
February 28, 2016 6M.M.C.P.
7. In synthetic organic and organometallic chemistry, solution-state
NMR means a 300-500 MHz NMR spectrometer, high-precision
glass sample tubes, 2 ml of deuterated solvent (typically fully
deuterated chloroform, acetone, benzene, or dichlorobenzene),
several milligrams of pure sample, and a reference substance,
NMR experiments with several hours of spectrometer time and
data interpretation.
The structures of new compounds with molecular weights up to
2000 Da can be determined, especially when analyzed along with
results from NMR databases and mass spectroscopy.
February 28, 2016 7M.M.C.P.
8. It is a well known fact that spectra given by all forms of
spectroscopy may be described in terms of the following three
important factors.
1. Frequency of spectral lines or bands.
2. Intensity of spectral lines or bands.
3. Shape of spectral lines or bands.
All above properties depends on the molecular parameters of the
system. In case of the NMR these molecular parameters are found
to be:
1. Shielding constant of nuclei.
2. Coupling constant of nuclei.
3. Lifetime of energy level.
February 28, 2016 8M.M.C.P.
9. NUCLEAR SPIN AND MAGNETIC MOMENT
Magnetic field
Nucleus axis
Nucleus
Fig: Spinning of Nucleus
February 28, 2016 9M.M.C.P.
10. All nuclei carry a charge. In some nuclei this charge spins on the
nuclear axis and this circulation of nuclear charge generates a
magnetic dipole along the axies.
The nuclei of atoms are composed of protons and neutrons. Like
electrons, these particle also have the properties to spin on their
own axis and each of them possesses angular momentum1/2(h/2π)
in accordance with the quantum theory. The net resultant of the
angular momentum of all nuclear particles is called nuclear spin.
For a nucleus having a spin quantum number I, these are(2I +1)
spin states.
February 28, 2016 10M.M.C.P.
11. Two properties of nuclear particles which are important in
understanding of NMR spectroscopy are:
• The net spin associated with the proton and neutron.
• The distribution of positive charge.
The net spin number or spin quantum number I of a particular
nucleus can be obtained by adding spin numbers of individual
proton and neutron of ½ each, assuming that neutrons cancel only
neutrons and protons cancel only protons, because of pairing or
spinning in opposite directions.
The spin number I have values 0,1/2, 1, 3/2, 5/2 and so forth. If
I=0 that represent no spin.
February 28, 2016 11M.M.C.P.
12. PRINCIPLE FOR NUCLEAR SPIN
If the sum of protons and neutrons is even, I is zero or
integral (0,1,2,3 …..)
If the sum of proton and neutrons is odd, I is a half
integral (1/2, 3/2, 5/2….)
If the both protons and neutrons are even numbered, I is
zero.
February 28, 2016 12M.M.C.P.
14. •The NMR is mostly consult with nucleus spin quantum no. (I)= ½ .
The proton having a I = ½ when place in external magnetic field
(Ho) it’s start to spin around the nuclear axis and generate a
another magnetic field.
•According to quantum mechanics there are 2I + 1 so two spin stage
+ ½ and - ½ for the proton.
I = ½
E
I = - ½
I = + ½
E2
E1
Ho
Spin state of proton
THEORY AND PRINCIPLE
February 28, 2016 14
M.M.C.P.
15. • When a charge particle place in magnetic field. It’s start to revel
and therefore it’s pusses angular movement due to generation of
another magnetic field. The charge particle with nucleus spin has
magnitude and direction. Both this property is describe by the
factor called as magnetic movement (µ).
•So, when the proton take place in magnetic field . It has two spin
steps + ½ and - ½ so, there are two energy level for spin steps + ½
& -½.
E1 = + ½ µ Ho ………………….1
E2 = - ½ µ Ho ……………….….2
where, Ho = magnetic field strength.
µ = magnetic movement
ΔE = E1 – E2 …………………....3
February 28, 2016 15M.M.C.P.
16. ΔE = µ Ho …………………………4
by Boher’s frequency eq. we can write
ΔE = hv ……………………….5 v= frequency
from the eq. 4 &5
hv = µ Ho ………………………… 6
so, µ Ho ………………………….7
h
This is a basic eq. in NMR spectroscopy.
February 28, 2016 16M.M.C.P.
v =
1.41 Tesla = 60 MHz
2.35 Tesla = 100 MHz
7.05 Tesla = 300 MHz
17. ᵦ α
ᵦ
α
α
α
ᵦ
Nuclear magnetic movement with
No magnetic field
Applied magnetic
field (Ho)
Ho
APPLIED FIELD AND PRECESSION
Spinning nuclei-magnetic moments
Some elements have isotopes with nuclei that behave as though
they were spinning about an axis much like the earth. The
spinning of charge particle generates a magnetic field. As a
consequence, the spinning nuclei behave as though they were tiny
bar magnets having a north and a south pole.
February 28, 2016 17M.M.C.P.
18. •Since a nucleus or an electron bears a charge, its spin gives rise to a
magnetic field that is analogous to the field produce when an electric
current is passed through a coil of wire. The resulting magnetic
dipole (µ) is oriented along the axis of spin and has a value that is
characteristic for each kind of particle.
∆E = µᵦHo
I= - ½
18
0energy
No
field
Applied
field Ho
E= µᵦHo
E= µᵦHo
I= + ½
February 28, 2016 M.M.C.P.
19. PRECESSION
PRECESSIONAL MOTION
•Because the proton is behaving as a spinning magnet, it can align
itself either with or opposed to an external magnetic field. It can
also
move a characteristic way under the influence of the external
magnet.
•Considering the behavior of a spinning top, the top has a spinning
motion around its axis. It also performs a slower waltz like motion
in which the spinning axis of top moves slowly around the vertical.
Thus is called “precessional motion” and the top is said to be
precessing around the vertical axis of the gravitational force of the
earth.
February 28, 2016 19M.M.C.P.
20. •Precession arises due to the interaction of spin and the gravitational
force acting downwards. This is the reason why only a spinning top
will precess; where as a static top will topple over.
•Since the proton is a spinning magnet, it will precess around the axis
of an applied external magnetic field. It will precess in two main
orientations.
•Aligned or parallel with the field-low energy.
•Opposed or anti parallel to the field-high energy.
February 28, 2016 20M.M.C.P.
21. PRECESSIONAL FREQUENCY
The precessional frequency of the nucleus is directly proportional
to the strength of external field and also depends on the nature of
the nuclear magnet.
Magnetic nuclei different atoms have different characteristic
precessional frequency.
according to Larmor precessional theory
ω = γH0 ………………1
where, ω= Larmor precessional frequency.
ω = 2 πV ………………2
2 πV = γH0 ………………..3
………………….4
V α H0 ..................................5
Where, γ = is gyromagnetic ratio =
V =
H0
February 28, 2016
21M.M.C.P.
Intrinsic magnetic dipole momentum
Spin angular momentum
2 π
γ
22. ENERGY TRANSITIONS
A proton when kept in an external magnetic field will precess
and can take one of the two orientations with respect to the axis
of
the external field. Either aligned or opposed.
If a proton is precessing in the aligned orientation it can absorbed
energy and pass into the opposed orientation and vice versa by
losing energy.
If we irradiate the precessing nuclei with a beam of radio
frequency, the low energy nuclei may absorb this energy and
move
to a higher energy state.February 28, 2016 22M.M.C.P.
23. The precessing proton will absorb energy from the radio frequency
source, if the precessing frequency same as the frequency of the
radio frequency beam.
When this occurs, the nucleus and radio frequency beam are said to
be resonance, hence the term “ nuclear magnetic resonance”.
February 28, 2016 23M.M.C.P.
24. WIDTH OF ABSORPTION LINES IN NMR
The separation of two absorption lines depends on how close
they are to each other and the absorption line width.
The width of the absorption line is affected by a number of
factors, only some of which we can control.
These are the factors:
I.The homogeneous field
II.Relaxation time
III.Magic angle NMR
IV.Other source of line broadening
February 28, 2016 24M.M.C.P.
25. 1. THE HOMOGENEOUS FIELD
The most important factor controlling the absorption line
width is the applied magnetic field H0.
It is very important that this field be constant over all
parts of the sample, which may be 1-2 inch long. If it is
not, H0 is different parts of the sample and therefore v,
the frequency of the absorbed radiation, will vary in
different parts of sample.
This variation results in a wide absorption line. For
qualitative or quantitative analysis a wide absorption line
is very undesirable, since we may get overlap between
neighbouring peaks.February 28, 2016 25M.M.C.P.
26. 2. RELAXATION TIME
The second important feature that influences the absorption line
width is the length of time that an excited nucleus stays in the
exited state.
ΔE Δt = constant
where, ΔE is the uncertain in the value of E
Δt is the length of time a nucleus of time a nucleus spends
in the excited state.
Since ΔE Δt is a constant, when Δt is small, ΔE is large. But we
know that E = hv and that h is constant.
Therefore any variation in E will result in a variation in v. If E is not
an exact number but varies over the range E+ ΔE, then v will not be
exact but vary over the corresponding range v + Δv. Then we have
E + ΔE = h(v + Δv)
February 28, 2016 26M.M.C.P.
27. We can summarize this relationship by saying that when Δt is
small, ΔE is large and therefore Δv is large. If Δv is large, then the
frequency range over which absorption takes place is wide and a
wide absorption line results.
There are two principle modes of relaxation,
1. Longitudinal relaxation /spin lattice
2. Transverse relaxation /spin spin
February 28, 2016 27M.M.C.P.
28. A. LONGITUDINAL RELAXATION
When the nucleus loses its excitation energy to the surrounding
molecules, the system becomes warm as the energy is changed to
heat.
This process is quite fast when the molecules are able to move
quickly. This is the state of affairs in liquid.
The excitation energy becomes dispersed throughout the whole
system of molecules in which the sample finds it self. No radiation
energy appears, no other nuclei become exited. Instead, as
numerous nuclei lose their energy in this fashion, the temperature
of the sample goes up. This process is called longitudinal
relaxation
T1.
February 28, 2016 28M.M.C.P.
29. B. TRANSVERSE RELAXATION
An excited nucleus may transfer its energy to an unexcited nucleus
of a similar molecules that is nearby.
In this process, the nearby unexcited nucleus becomes excited a
the previously excited nucleus become unexcited.
There is no net change in energy of the system, but the length of
the time that one nucleus stays excited is shortened. This process,
which is called transverse relaxation T2.
February 28, 2016 29M.M.C.P.
30. 3. MAGIC ANGLE NMR
A problem with the examination of solids that the nuclei can be
frozen in space and cannot freely line up in magnetic field.
The NMR signals generated are dependent among other things, on
the orientation of the nuclei. The randomly oriented nuclei
therefore give broad band spectra which are not very useful
analytically.
It can be shown that when one rotates a solid sample such that its
axis of rotation 54.70
to the direction of the applied magnetic field,
the broadening caused by random nuclear orientations tends to be
average out, resulting in narrower spectra.
February 28, 2016 30M.M.C.P.
31. This is more useful analytically because it allow better
resolution and therefor better measurement of chemical shift
and spin-spin splitting. In turn, this is very informative of the
functional group and their positions relative to each other in the
sample molecule.
February 28, 2016 31M.M.C.P.
32. 4. OTHER SOURCES OF LINE BROADENING
Any process of deactivating, or relaxing, an excited molecule
results in a decrease in a lifetime of the excited state. This is turn
causes line broadening.
Other causes of deactivation include
1. The presence of ions
2. Paramagnetic molecules
3. Nuclei with quadrupole moment
February 28, 2016 32M.M.C.P.
33. 1.INDUCED MAGNETIC FIELD1.INDUCED MAGNETIC FIELD :-:-
In the applied magnetic field, the valence electrons around the
nucleus are cause to circulates and they generates their own
secondary magnetic field is known as induced magnetic field.induced magnetic field.
2.SHIELDING:-2.SHIELDING:-
The circulation of electron around the protons itself generates field
in a such way that , it oppose the applied field.
The field felt by the protons is thus diminished and the proton is
said to be shieldedshielded and the absorption said to be upfield.upfield.
February 28, 2016 33M.M.C.P.
SHIELDING AND DESHIELDING
34. DESHIELDINGDESHIELDING:-
If the induced magnetic field reinforced the applied magnetic
field ,then the field felt by the proton is augmentedaugmented and the proton
is said to be deshieldeddeshielded and the absorption is known as downfield.downfield.
February 28, 2016 34M.M.C.P.
35. Compare with naked proton, a shielded proton required
higher applied field strength than the deshielded protons.
Shifts in the position of NMR absorption arising from
shielding and deshielding by electron, due to different chemical
environments around protons are called chemical shift.chemical shift.
Generally chemical shift measured from the signal of
reference standard such as TMS
February 28, 2016 35M.M.C.P.
36. The extent of shielding is represented in terms of
shielding parameter α. When absorption occurs, the
field H felt by the proton is represented as,
H = HH = H00 (1 -(1 - αα )………………. 1)………………. 1
where, H0 = applied field strength.
Greater value of α, greater will be the value of
applied strength which has to be applied to get the
effective field required for absorption and vice
versa. ………………. 2
From 1 and 2
February 28, 2016 36M.M.C.P.
HH00
37. It is clear that the proton with different electronic
environments or with shielding parameter can be brought
into resonance in two ways
1. The strength of external field is kept steady and the radio
frequency is constantly varied
2. The radio frequency is kept steady and strength of the
applied field is constantly varied.
Clearly at constant radio frequency, shielding shift the
absorption upfield in the molecules where these is a
spherical distribution of electrons around the proton,
It is called positive shielding.
February 28, 2016 37M.M.C.P.
39. CHARACTERISTICS:-CHARACTERISTICS:-
Chemical inertness
Magnetically neutral
Gives single sharp peak
Easily recognizable peak
Miscible with wide range of solvents
Volatility –to facilitate recovery from valuable samples
February 28, 2016 39M.M.C.P.
REFERENCE STANDARDS
40. 1.TMS(Tetra Methyl Silan):-1.TMS(Tetra Methyl Silan):-
It is generally used as internal standard for measuring the
position of 1
H,13
C, 29
Si in NMR
TMS at 0.5%0.5% concentration is used normally
TMS has 12 protons which are uniformly shielded because of
highly electro-positivehighly electro-positive nature of silicon at centre
Hence this 12 protons gives single sharp peak at ooδδ which
require maximum magnetic field than protons of the most
organic compounds
It is chemically inert and miscible with large range of solvents
Highly volatile and easily removed to get back the sample
February 28, 2016 40M.M.C.P.
41. It does not take part in intermolecular association
with the sample
It’s all protons are magnetically equivalent
TMS can be used as an external referenceexternal reference also.
February 28, 2016 41M.M.C.P.
42. 2.Sodium salts of 3-(trimethyl silyl)propane2.Sodium salts of 3-(trimethyl silyl)propane
sulphonate:-sulphonate:-
It is a water soluble compound.
It is used as internal standard for running PMR
spectra of water soluble substances in the duterium
oxide solvent.
February 28, 2016 42M.M.C.P.
43. ““Chemical shift is the difference between the absorption position
of the sample proton and the absorption position of reference
standard”
Variations of the positions of NMR absorptions due to the
electronic shielding and deshielding.
February 28, 2016 43M.M.C.P.
CHEMICAL SHIFTCHEMICAL SHIFT
44. Chemical Shifts….
• Measured in parts per million (ppm).
• It is the ratio of shift downfield from TMS (Hz) to total
spectrometer frequency (MHz).
• The chemical shift is independent of the operating
frequency of the spectrometer.
• Same value for 60, 100, or 300 MHz machine.
• Common scale used is the delta (δ) scale.
February 28, 2016 44M.M.C.P.
45. MEASUREMENT OF CHEMICAL SHIFTMEASUREMENT OF CHEMICAL SHIFT
Each proton in a molecule has slightly different
chemical environment and consequently has a slightly
different amount of electronic shielding, which results
in a slightly different resonance frequency. These
differences in resonance frequency are very small.
For example, the difference between the resonance
frequencies of the protons in Chloromethane and in
Fluromethane is only 60 MHz when the applied field is
1.41 Tesla.
February 28, 2016 45M.M.C.P.
46. Since the radiation used to induce proton spin
transitions at that magnetic field strength is of a frequency near
60 MHz, the difference between Chloromethane and
Fluoromethane represents a change in frequency of only slightly,
not more than one part per million.
It is very difficult to measure the exact resonance frequencies to
that precision. Hence instead of measurement of the exact radio
frequency of any proton, a reference compound is placed in the
solution of the substance to be measured and the resonance
frequency of each proton in the sample is measured relative to the
resonance frequency of the protons of the substance.
February 28, 2016 46M.M.C.P.
47. The standard reference substance used universally
is TETRAMETHYLSILANE (TMS), the standard
reference is also known as Internal Standard.
Chemical Shift, ppm δ =
Shift from TMS in Hz
Spectrometer frequency (MHz)
Eg: for CH3Br protons, chemical shift from TMS = 162Hz in a
60 MHz instrument and 270Hz in a 100 MHz instrument.
Calculate δ value.
δ = 162Hz / 60 MHz = 270 / 100 = 2.7ppm
Hence, δ Value remains same irrespective of the spectrometer.
X 101066
February 28, 2016 47M.M.C.P.
48. Chemical shift is measure in three major spectra.
Delta(δ)
Tau scale(τ)
Hertz (Hz)
5 4 3 2 1 0
Up field shielding
Down field shielding
δ scale
5 6 7 8 9 10 Τ scale
1000 800 400 100 HZ
February 28, 2016 48M.M.C.P.
49. Each δ unit is 1 ppm difference from TMS 60Hz and 300Hz
February 28, 2016 49M.M.C.P.
1 ppm = 60 Hz = 6 ͯ 10
-5
MHz
1 ppm = 300 Hz = 3 ͯ 10 MHz
-4
50. CHART FOR DIFFERENT TYPES OFCHART FOR DIFFERENT TYPES OF
PROTON CHEMICAL SHIFT VALUESPROTON CHEMICAL SHIFT VALUES
February 28, 2016 50M.M.C.P.
51. BASIC CONCEPTS….BASIC CONCEPTS….
1) The chemical shift or position of line in NMR spectrum gives
information on molecular environment of the nuclei from
which it arises.
2) The chemical shift of nuclei in the different molecules are
similar. If the molecular magnetic environment are similar.
3) The intensity of lines gives directly the relative number of
magnetically active nuclei undergoing the different chemical
shift.
4) The chemical shift is used for the identification of functional
groups and as an aid in determining structural arrangement of
groups.
February 28, 2016 51M.M.C.P.
52. 5)Greater is the deshielding of proton
higher will be the value of delta.
Greater is the shielding of proton
lower will be the value of delta.
6)Electron withdrawing substituents like halogens
which deshielded the protons.
Electron releasing substituents like alkyl groups
which shielded the protons.
7)The delta unit is independent of shield strength.
Chemical shift position measured in the Hz are field
dependent.
February 28, 2016 52M.M.C.P.
53. • Electronegativity Effects.
• Van der Waal’s Deshielding.
• Hydrogen Bonding.
• Magnetic Anisotropy.
• Concentration, Tempareture and Solvent
Effect.
February 28, 2016 53M.M.C.P.
FACTORS INFLUENCING CHEMICAL SHIFT
54. ELECTRONEGATIVITY EFFECTSELECTRONEGATIVITY EFFECTS :-:-
• The chemical shift simply increase as the electronegativity of
the attached element increases.
• Following table illustrates this relationship for several
compounds of the type CH3X.
February 28, 2016 54M.M.C.P.
55. • Multiple substituents have a stronger effect than a single
substituent. The influence of the substituent drops off rapidly
with distance, an electronegative element having little effect
on protons that are more than three carbons distant. This effect
is illustrated in the following table.
February 28, 2016 55M.M.C.P.
56. Electronegative substituents attached to a carbon atom reduces
that valence electron density around the protons attached to
that carbon due to their electron withdrawing effects.
Electronegative substituents on carbon reduce the diamagnetic
shielding in the neighborhood of the attached protons because
they reduce the electron density around those protons.
The greater the electronegativity of the substituents, the more
deshielding of protons and hence the greater is the Chemical
Shift of those protons.
February 28, 2016 56M.M.C.P.
58. HYDROGEN BONDINGHYDROGEN BONDING :-:-
Hydrogen atom exhibit property of hydrogen bonding in a
compound which absorbs at a low field in comparison to the one
which does not shows hydrogen bonding.
Hydrogen bonded proton being attached to a highly
electronegative atom will have smaller electron density around
it. less shielded resonance will occurs downfield and
downfield shift depends up on the strength of hydrogen bonding.
Intramolecular and Intermolecular hydrogen bonding can be
easily distinguished as the latter does not show any shift in
absorption due to change in concentration.
February 28, 2016 58M.M.C.P.
59. In case of phenols. Absorption occurs between 4-8 δ but if the
concentration is decrease and volume of carbon tetrachloride is
increase then absorption of OH proton occurs upfield,
Exchangeable Hydrogen: protons that exhibit hydrogen bonding (
eg. Hydroxyl or amino protons ) show resonance over a wide
range. These protons are usually found to attached to a
heteroatom.
The more hydrogen bonding that takes place, the more deshielded
proton becomes.
February 28, 2016 59M.M.C.P.
60. MAGNETIC ANISOTROPYMAGNETIC ANISOTROPY :-:-
Circulation of electrons, especially the π electrons near by
nuclei generates an induced field which can either oppose or
reinforced the applied field at proton, depending upon location
of proton or space occupied by the protons.
In case of alkynes, shielding occurs but in case of alkenes,
benzene and aldehydes deshielding takes place.
The occurrence of shielding and deshielding can be determined
by the location of proton in the space and so this effect is known
as space effect.
February 28, 2016 60M.M.C.P.
61. • There are some types of protons whose chemical shifts are not
easily explained by simple consideration of the electronegativity of
the attached groups.
• For example, when benzene is placed in magnetic field, the π
electrons in the aromatic ring system are induced to circulate
around the ring. This circulation is called as Ring current. The
moving electrons generate a magnetic field which influence the
shielding of the benzene hydrogens.
February 28, 2016 61M.M.C.P.
62. Diamagnetic anisotropy in Benzene
Circulating π
electron
Secondary magnetic
field generated by
circulating π electrons
which deshields
aromatic protons
Applied field B0
February 28, 2016 62M.M.C.P.
63. The benzene hydrogens are said to be deshielded by the
diamagnetic anisotropy of the ring.
In electromagnetic terminology; an Isotropic field is one
of either uniform density or spherically symmetric
distribution.
Anisotropic field is nonuniform. In case of benzene
labile electrons in the ring interact with the applied field
and thus rendered it anisotropic.
February 28, 2016 63M.M.C.P.
64. Thus a proton attached to a benzene ring is influenced by three
magnetic fields:
1)The strong magnetic field applied by the electromagnets of the
NMR spectrophotometer.
2)Weak magnetic field due to shielding by the valence electrons
around the proton.
3)Anisotropy generated by the ring-system π electrons.
So anisotropic effect gives the benzene protons at higher
resonance δ value.
February 28, 2016 64M.M.C.P.
65. • All groups in a molecule that have π electrons generate
secondary anisotropic fields.
• In Acetylene the magnetic field generated by induced
circulation of the π electrons has a geometry such that the
acetylenic hydrogens are shielded. Hence acetylenic
hydrogens have resonance at higher field.
Diamagnetic anisotropy
in Acetylene
π
February 28, 2016 65M.M.C.P.
66. VAN DER WAAL’S DESHIELDING :-VAN DER WAAL’S DESHIELDING :-
In the overcrowded molecules. It is possible that some
proton may be occupying stearic hindered position.
Clearly electron cloud of bulky group or hindering
group will tend to repel the electron cloud surrounding
the proton and such proton will shielded and will
resonate at slightly higher value of δ than expected in
the absence of this effect.
February 28, 2016 66M.M.C.P.
67. CONCENTRATION, TEMPERATURE ANDCONCENTRATION, TEMPERATURE AND
SOLVENT EFFECT :-SOLVENT EFFECT :-
In ccl4 and cdcl3 chemical shift of proton attached to carbon is
independent of concentration and temperature, while proton of
-OH, –NH2, –SH groups exhibits a substantial conc. and
temperature effects due to the hydrogen bonding
The intermolecular hydrogen bonding is less affected than
intramolecular bonding by concentration change
Both type of hydrogen bonding affected by the temperature
variation
February 28, 2016 67M.M.C.P.
68. NMR spectrum of a substance gives very valuable information about
its molecular structure. This information is gathered as follows :
(1)The number signalsnumber signals in PMR spectrum tell us how many kinds
of protons in different chemical environments are present in
structure under examination
(2)The position of signalposition of signal tell us about the electronic environment
of each kind of proton
(3)The intensities of different signalsintensities of different signals tell us about the relative
number of protons of different kind
(4)The splitting of signalssplitting of signals tell us about environment of the
absorbing protons with respect to the environments of neighboring
protons
February 28, 2016 68M.M.C.P.
INTERPRETATION OF PMR SPECTRAINTERPRETATION OF PMR SPECTRA
75. 1. Conventional/Continuous NMR spectrophotometer
Minimal type.
Multiple type.
Wide line.
Or
It can also be classified as
a. Single coil spectrophotometer
b. Two coil spectrophotometer
2. Pulsed Fourier transforms NMR spectrophotometer
CLASSIFICATION OF THE NMR
SPECTROPHOTOMETERS
75February 28, 2016 M.M.C.P.
76. COMPONENTS OF THE
SPECTROPHOTOMETER
Basically NMR instrumentation involves the following units.
1.A magnet to separate the nuclear spin energy state.
2. Two RF channels, one for the field/frequency stabilization and one to
supply RF irradiating energy.
3. A sample probe containing coils for coupling the sample with the RF
field;
it consists of Sample holder, RF oscillator, Sweep generator and RF
receiver.
4. A detector to process the NMR signals.
5. A recorder to display the spectrum.
76February 28, 2016 M.M.C.P.
78. •It is used to supply the principal part of the field Ho, which determines the
Larmer frequency of any nucleus.
•The stronger the magnetic field, the better the line separation of chemically
shifted nuclei on the frequency scale.
•The relative populations of the lower energy spin level increases with the
increasing field, leading to a corresponding increase in the sensitivity of the
NMR experiment.
MAGNETS
FEATURES:
1. It should give homogeneous magnetic field i.e.; the strength and direction of
the magnetic field should be constant over longer periods.
2. The strength of the field should be very high at least 20,000 gaus.
78February 28, 2016 M.M.C.P.
79. TYPES OF MAGNETS:
1. PERMANENT magnets
2. ELECTRO magnets and
3. SUPER CONDUCTING magnets
MAGNETIC COILS
It is not easy or convenient to vary the magnetic field of large stable
magnets, however this problem can be overcome by superimposing a
small variable magnetic field on the main field.
Using a pair of Helmholtz coils on the pole faces of the permanent
magnet does this. These coils induce a magnetic field that can be varied
by varying the current flowing through them.
The small magnetic field is produced in the same direction as the main
field and is added to it. The sample is exposed to both fields, which
appear one field to the nucleus.
79February 28, 2016 M.M.C.P.
80. THE PROBE UNIT
It is a sensing element of the spectrophotometer system. It is inserted between the
pole faces of the magnet in X-Y plane of the magnet air gap an adjustable probe
holder.
So the sample in NMR experiment experiences the combined effect of two
magnetic fields ie Ho and RF (EMR).
The usual NMR sample cell is generally made up of the glass, which is strong and
cheap. It consist of a 5 mm outer diameter and 7.5 cm long glass tube containing
0.4 ml of liquid.
The sample tube in NMR is held vertically between the poles faces of the magnet.
The probe contains a sample holder, sweep source and detector coils, with the
reference cell. The detector and receiver coils are orientated at 90 to each other.
The sample probe rotates the sample tube at a 30-40 revolutions on the longitudinal
axis. Each part of the sample tube experiences the same time average the field.
80February 28, 2016 M.M.C.P.
81. THE RADIOFREQUENCY GENERATOR
Using an RF oscillator creates the radio frequency radiation, required to
induce transition in the nuclei of the sample from the ground state to
excited states.
The source is highly stable crystal controlled oscillator. It is mounted at
the right angles to the path of the field of wound around the sample tube
perpendicular to the magnetic field to get maximum interaction with the
sample. The oscillator irradiates the sample with RF radiation.
Radio frequencies are generated by the electronic multiplication of natural
frequency of a quartz crystal contained in a thermo stated block.
In order to generate radiofrequency radiation, RFO is used. To achieve
the maximum interaction of the RFradiation with the sample, the coil of
oscillator is wound around the sample container.
81February 28, 2016 M.M.C.P.
82. The RFO coil is installed perpendicular (90 ºC) to the applied magnetic field
and transmits radio waves of fixed frequency such as 60,100,200 or 300
MHz to a small coil that energies the sample in the probe.
This is done so that the applied RF field should not change the effective
magnetic field in the process of irradiation.
82February 28, 2016 M.M.C.P.
83. SWEEP GENERATOR
Resonance
This can achieved by two methods
•Frequency sweep method
If the applied magnetic field is kept constant, the precession frequency is
fixed. In order to bring about resonance, the frequency of the RF field
should be changed so that it is becomes equal to the resonance
frequency.
83
Thus resonance condition is reached by the holding the applied magnetic
field Ho constant and scanning the Rf transmitter through the
frequencies, until the various nuclei come to resonance in turn as their
precessional frequency matched by the scanning source.
February 28, 2016 M.M.C.P.
84. •Field sweep method
•There is a relationship between the resonance frequency of the nucleus
and the strength of the magnetic field in which the sample is placed.
•If the RF radiation is constant, in order to bring their resonance, the
precession of the nucleus is to be changed by changing the applied
magnetic field.
•Generally the field sweep method is regarded as better because it is easier
to vary the magnetic field than the RF radiation so as to bring about
resonance in nuclei.
84February 28, 2016 M.M.C.P.
85. •Practically it is not very easy to vary the magnetic field of a large stable
magnet. This is technical problem is solved by superimposing a small
variable magnetic field on the main field.
•Helmholtz coils
85February 28, 2016 M.M.C.P.
86. RADIO FREQUENCY RECEIVER OR
DETECTOR
A few turns of wire is wound around the sample tube lightly. The receiver
coil is perpendicular to both the external magnetic and radiofrequency
transmitter coil.
When RF radiation is passed through the magnetised sample, resonance
occurs which cause the current voltage across the coil to drop.
This electrical signal is small and is usually amplified before recording.
Detection of NMR.
When the radiofrequency radiation is passed through the magnetised
sample two phenomena namely absorption and dispersion may occur.
The absorption of either signal will enable the resonance frequency to be
determined. It is found that the interpretation of absorption spectrum is
easier as compared to the dispersion spectrum.
The detector should be capable of separating absorption signal from
dispersion signals.
86February 28, 2016 M.M.C.P.
87. THERE ARE TWO WAYS OF DETECTING THE NMR PHENOMENA
1. Radio frequency bridge (single coil detection)
2. Nuclear detection (crossed coil detection)
SINGLE COIL METHOD
Single coil probe has one coil that not only supplies the RF radiation to the
sample but also serves as part of the detector circuit for the NMR
absorption signal. To detect the resonance absorption and to separate the
NMR signal from the imposed RF field, a RF bridge is used.
At the fixed frequency the current flowing through the coils wrapped
around the pole pieces of the magnet is varied. At the resonance there is
a imbalance generated in this coil by virtue of the developing
magnetization of the sample and this out of balance is detected in RF
circuit.
This technique is widely used in modern NMR spectrophotometer.
87February 28, 2016 M.M.C.P.
89. CROSSED COIL PROBES
Nuclear induction has two coils, one for the irradiating the sample and second
coil mounted orthogonally for the signal detection.
The irradiating coil oriented with its axis perpendicular to the magnetic field (i.e.
along the x-axis). The detector coil is wound around the sample tube with its
axis is the (y-axis) perpendicular to the both Ho (z-axis).
The RF current in the first coil wound around the x-axis excites the nuclei.
The nuclei induction in the second coil wound around the y-axis is
detected. The number of turns in the coil determines the particular
frequency involved.
The RF detector can be tuned to detect either a signal in the absorption
mode or in the dispersion mode. Phase sensitive detector is used which
helping the operator to select the phase of the signal to be detected.
89February 28, 2016 M.M.C.P.
92. WORKING
In the CW spectrometers the spectra can be recorded either with field sweep or
frequency sweep.
Keeping the frequency constant, while the magnetic field is varied, (swept) is
technically easier than holding the magnetic field constant and varying the
frequency.
The sample (0.5 mg) is dissolved in a solvent containing no interfering protons
usually CCl4
or CdCl3
0.5 ml and a small amount of TMS is added to serve as
an internal reference.
The sample cell is a small cylindrical glass tube that is suspended in the gap
between the faces of the pole pieces of the magnet. The sample cell is rotated
around its axis to ensure that all parts of the solution experience a relatively
uniform magnetic field. This increases the resolution of the spectrum.
92February 28, 2016 M.M.C.P.
93. Also in the magnetic gap, the radio frequency oscillator coil is installed
perpendicular (90˚) to the applied magnetic field.
This coil supplies the electromagnetic energy used to change the spin
orientations
of the protons.
Detector coil is arranged perpendicular to the RF oscillator coil. As the magnetic
field strength is increased, the precessional frequencies of all the nucleus
increases (a peak or series of peaks)
As the magnetic field strength is increased linearly, a pen travels from left to the
right on a recording chart.
As each chemically distinct type of proton comes into resonance, it is record as a
peak on the chart. The peak δ=0 ppm is due to the internal reference compound
TMS.
93February 28, 2016 M.M.C.P.
94. Instruments which vary the magnetic field in a continuos fashion scanning from
the downfield end to upfield end of the spectrum, are called continuous wave
instruments.
Because the chemical shifts of the peaks in this spectrum are calculated from the
frequency differences from the TMS, this type of spectrum is said to be frequency
domain spectrum.
Since highly shielded protons precess more slowly than relatively deshielded
protons. Hence highly shielded protons appear to the right of the chart, and less
shielded or dishelded protons appear to the left.
The region of the chart to the left is sometimes said to be downfield and that to
the right is said to be upfield.
94February 28, 2016 M.M.C.P.
95. Peaks generated by a CW instrument have ringing. Ringing occurs because the
excited nuclei do not have time to relax back to their equilibrium state. And pen
of the instrument have advanced to a new position. Ringing is
most noticeable when a peak is a sharp singlet.
95February 28, 2016 M.M.C.P.
96. TYPES OF CONTINUOUS –WAVE (CW)
INSTRUMENT
1. Minimal-type NMR spectrometer
This basic instrument often utilizes a permanent of 14, 21 or 23 K gaus field
strength and RF fields of 60, 90 or 100 MHz respectively.
Each frequency needed for the selected magnetic nuclei is synthesized from a
suitable harmonic of a 15 MHz crystal oscillator and mixed with the output of
an appropriate low frequency incremental oscillator.
The minimal type has,
1. Stressed reliability
2. Ease of operation
3. High performance
4. Low cost
96February 28, 2016 M.M.C.P.
97. 2. Multipurpose NMR spectrometers
These instruments are designed primarily for research, high performance,
expensive and versatility better than minimal type.
The high precision comes through the use of homonuclear and heteronuclear
lock systems and frequency synthesizers.
They are also characterized by high intrinsic sensitivity and the ability to study a
variety of nuclei.
The strength of the magnetic field is quite important since sensitivity, resolution
and the separation of chemically shifted peaks increase as the field strength
increases.
These instruments uses RF field of 220,300 or even 500MHz.
97February 28, 2016 M.M.C.P.
98. 3. Wild-line CW NMR spectrometer
The wild line NMR spectrometer uses a frequency synthesizer to generate the RF
field and a permanent magnet or a compact lightweight electromagnet.
Slowly varying scan voltages are directly injected in the regulator for the magnet
power supply for the electromagnet. Sample probe temperatures may be varied
over the range 170 to 2000 ºC.
Sample tubes are 15-18mm in outer diameter. The std magnetic field is 9.4 K
gaus for protons and 10 K gaus for F19;the RF field is 40 MHz.
Instruments are also available in which RF applied field is continuously
adjustable over a basic frequency range of 300 Hz to 31MHz usually in steps of
10 Hz.
For signal detection a sweep unit generates audio-modulation voltages
that have selectable frequencies of 20,40,80,200 and 400 MHz.
The output is amplified for simultaneous application to the probe modulation
coils and to the oscilloscope.
98February 28, 2016 M.M.C.P.
99. THE PULSED FOURIER TRANSFORM (FT )
INSTRUMENT
•The continuous wave type of NMR spectrometer operates by exciting the nuclei
of the isotope under observation one type at a time.
•In the case of H1 nuclei each distinct type of proton (phenyl, vinyl, methyl and so
on) is excited individually and its resonance peak is observed and recorded,
independently of all the others. As we look at first one type of hydrogen and then
another scanning until all of the types have come into resonance.
•An alternative approach common to modern sophisticated instrument is to use a
powerful but short burst of energy called a pulse that excites all of the magnetic
nuclei in the molecule simultaneously and all the signals are collected at the same
time with a computer.
•In an organic molecule for instance all of the H1 nuclei are induced to undergo
resonance at the same time.
99February 28, 2016 M.M.C.P.
100. •When the pulse is discontinued the excited nuclei begin to lose their excitation
energy and return to the original state or relax. As each excited nucleus relaxes it
emits EMR.
•Since the molecule contains many different nuclei many different frequencies of
EMR are emitted simultaneously. This emission is called a free-induction decay
(FID) signal.
•The intensity of FID decays with the time as all of the frequencies emitted and can
be quite complex. We usually extract individual frequencies due to different
nuclei
by using a computer and a mathematical method called a Fourier-transform
analysis.
•The Fourier transform breaks the FID into its separate since or cosine wave
components. This procedure is too complex to be carried out by eye or by hand; it
requires a computer.
•The pulse actually contains a range of frequencies centered about the hydrogen in
the molecule at once this signal burst of energy.
100February 28, 2016 M.M.C.P.
101. ADVANTAGES OF FT-NMR
FT-NMR is more sensitive and can measure weaker signals.
The pulsed FT-NMR is much faster (seconds instead of min) as compared to
continuous wave NMR.
FT-NMR can be obtained with less than 0.5 mg of compound. This is important
in the biological chemistry, where only μg quantities of the material may be
available.
The FT method also gives improved spectra for sparingly soluble compounds.
Pulsed FT-NMR is therefore especially suitable for the examination of nuclei
that are magnetic or very dilute samples.
101February 28, 2016 M.M.C.P.
103. COMPONENTS OF FT-NMR
A simplified form of the block diagram showing the instrument components of a
typical Fourier transform NMR spectrometer.
The central component of the instrument is a highly stable magnet in which the
sample is placed.
The sample is surrounded by the transmitter/receiver coil.
A crystal controlled frequency synthesizer having an output frequency of Vc
produces radio-frequency radiation.
This signal passes into a pulse switch and power amplifier, which creates an
intense and reproducible pulse of RF current in the transmitter coil.
Resulting signal is picked up by the same coil which now serves a as
receiver.
103February 28, 2016 M.M.C.P.
104. The detector circuitry produced the difference between the nuclear signals
Vn and the crystal oscillator output Vc which leads to the low frequency
time-domain signal as shown in the fig.
This signal is digitalized and collected in the memory of the computer for
analysis by a Fourier transform program and other data analysis software.
The output from this program is plotted giving a frequency domain
spectrum.
104February 28, 2016 M.M.C.P.
The signal is then amplified and transmitted to a phase sensitive detector.
105. SAMPLE HANDLING TECHNIQUES IN
NMR SPECTROSCOPY
The sample is placed in the probe, which contains the transmitter and receiver coils
and a spinner to spin the tube about its vertical axis in order to average out field in
homogeneities. In the electromagnet, the tube spins at right angles to the Z axis,
which is horizontal, where as in the superconducting magnet, the tube fits in the
bore.
A routine sample for proton NMR on a scanning
60 MHz instrument consists about 5 – 20mg of the sample in about 0.4ml of the
solvent in a 5mm glass tube.
500MHz instrument consists about less than 1μg of the sample of modest
molecular weight in a microtube.
IDEAL SAMPLE SIZE
For continuous wave spectra – less than 50mg.
For FT spectra 1 – 10mg
105February 28, 2016 M.M.C.P.
106. IDEAL SOLVENTS
Inert
Non polar
Low boiling point
Inexpensive
Should contain no protons
COMMONLY USED SOLVENTS
CCl4
CdCl3
DMSO
D2O
Cd3OD
106February 28, 2016 M.M.C.P.
107. • Each signal in an NMR spectrum represents
one kind or one set of protons in a molecule.
• It is found that in certain molecules, a single
peak (singlet) is not observed, but instead, a
multiplet (groups of peaks) is observed.
SPLITTING OF THE SIGNALSSPLITTING OF THE SIGNALS
February 28, 2016 107M.M.C.P.
108. E.g. A molecule of CH3CH2Br, ethyl bromide.
February 28, 2016 108M.M.C.P.
109. SPIN-SPIN COUPLING
• The interaction between two or more protons, most
often through the bonds, results in splitting of the
spectral lines.
• It is related to the number of possible combinations of
the spin orientations of the neighboring protons.
• The magnitude of the spin coupling interaction
between protons in general decreases as the number
of bonds between the coupled nuclei increases.
February 28, 2016 109M.M.C.P.
110. Consider a molecule of ethyl bromide (CH3-CH2-Br).the
spin of two protons (-CH2-) can couple with the
adjacent methyl group (-CH3-) in three different ways
relative to the external field . The three different ways of
alignment are ;
Thus a triplet of peaks results with the intensity ratio of
1 : 2 : 1 which corresponds to the distribution ratio of
alignment .
February 28, 2016 110M.M.C.P.
111. Similarly the spin of three protons (CH3-) can couple
with the adjacent methylene group (-CH2-) in four
different ways relative to the external field
Thus a quartet of peaks results with an intensity ratio of 1:3:3:1
which corresponds to the distribution ratio of all the alignment.
February 28, 2016 111M.M.C.P.
112. • The relative intensities of the individual lines of a
multiplet corresponds to the lines in the binomial
expression .
• If n=1, then (1+x)n
= 1 + x.
• If n=2, then (1+ x )2
= 1+2x + x2
, thus the lines of
triplet have relative intensities 1: 2 :1.
• If n=3, then ( 1 + x )3
= 1 +3X + 3X + X3
, the lines
of quartet have relative intensities 1 : 3: 3 : 1.
February 28, 2016 112M.M.C.P.
113. Often a group of hydrogen's will appear as a multiplet
rather than as a single peak.
Multiplets are named as follows:
Singlet Quintet
Doublet Sextet Septet
Triplet Octet
Quartet Nonet
This happens because of interaction with neighboring
hydrogens and is called,
SPIN-SPIN SPLITTING.
February 28, 2016 113
M.M.C.P.
114. C CH
Cl
Cl H
H
Cl
integral = 2
integral = 1
triplet doublet
1,1,2-Trichloroethane1,1,2-Trichloroethane
The two kinds of hydrogens do not appear as single peaks,
rather there is a “triplet” and a “doublet”.
The sub peaks are due to
spin-spin splitting and are
predicted by the n+1 rule.
February 28, 2016 114M.M.C.P.
115. nn + 1 RULE+ 1 RULE
February 28, 2016 115M.M.C.P.
117. C C
H H
H
C C
H H
H
two neighbors
n+1 = 3
triplet
one neighbor
n+1 = 2
doublet
singlet
doublet
triplet
quartet
quintet
sextet
septet
MULTIPLETSthis hydrogen’s peak
is split by its two neighbors
these hydrogens are
split by their single
neighbor
February 28, 2016 117M.M.C.P.
118. EXCEPTIONS TO THE n+1 RULEEXCEPTIONS TO THE n+1 RULE
IMPORTANT !
Protons that are equivalent by symmetry
usually do not split one another
CH CHX Y CH2 CH2X Y
no splitting if x=y no splitting if x=y
1)
2) Protons in the same group
usually do not split one another
C
H
H
H or C
H
H
February 28, 2016
118
M.M.C.P.
119. 3) The n+1 rule applies principally to protons in
aliphatic (saturated) chains or on saturated rings.
Con….Con….
CH2CH2CH2CH2CH3
CH3
Hor
but does not apply (in the simple way shown here)
to protons on double bonds or on benzene rings.
CH3
H
H
H
CH3
NONO
NONO
YESYES YESYES
February 28, 2016 119M.M.C.P.
121. 1 2 1
PASCAL’S TRIANGLEPASCAL’S TRIANGLE
1
1 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
1 6 15 20 15 6 1
1 7 21 35 35 21 7 1
singlet
doublet
triplet
quartet
quintet
sextet
septet
octet
The interior
entries are
the sums of
the two
numbers
immediately
above.
Intensities of
multiplet peaks
February 28, 2016
121
M.M.C.P.
122. The simple rule to find the multiplicity of the signal from a
group of protons, is to count the number of neighbours (n) &
add 1. That is (n+1) .
No coupled
hydrogen
One coupled
hydrogen
Two coupled
hydrogen
Three coupled
hydrogen
C
C –C – C –H
C
H
C- C – C –H
C
H
H - C –C-H
C
H
H - C – C- H
H
A singlet
A doublet
A triplet
A quartet
J
J
J
J
J
J
February 28, 2016 122M.M.C.P.
123. THE ORIGIN OFTHE ORIGIN OF
SPIN-SPIN SPLITTINGSPIN-SPIN SPLITTING
HOW IT HAPPENS ?
February 28, 2016 123M.M.C.P.
124. C C
H H
C C
H HA A
upfielddownfield
Bo
THE CHEMICAL SHIFT OF PROTON HTHE CHEMICAL SHIFT OF PROTON HAA ISIS
AFFECTED BY THE SPIN OF ITS NEIGHBOURSAFFECTED BY THE SPIN OF ITS NEIGHBOURS
50 % of
molecules
50 % of
molecules
At any given time about half of the molecules in solution will
have spin +1/2 and the other half will have spin -1/2.
aligned with Bo opposed to Bo
neighbor aligned neighbor opposed
+1/2 -1/2
February 28, 2016 124M.M.C.P.
125. C C
H H
C C
H H
one neighbor
n+1 = 2
doublet
one neighbor
n+1 = 2
doublet
SPIN ARRANGEMENTSSPIN ARRANGEMENTS
The resonance positions (splitting) of a given hydrogen is
affected by the possible spins of its neighbor.
February 28, 2016 125M.M.C.P.
126. C C
H H
H
C C
H H
H
two neighbors
n+1 = 3
triplet
one neighbor
n+1 = 2
doublet
SPIN ARRANGEMENTSSPIN ARRANGEMENTS
methylene spins
methine spins
February 28, 2016 126M.M.C.P.
127. three neighbors
n+1 = 4
quartet
two neighbors
n+1 = 3
triplet
SPIN ARRANGEMENTSSPIN ARRANGEMENTS
C C
H H
H
H
H
C C
H H
H
H
H
methyl spins methylene spinsFebruary 28, 2016
127M.M.C.P.
128. 128
NMR Spectroscopy
NOMENCLATURE
• The spacing between the two adjacent peaks of a multiplet is referred to as
the J or coupling constant
• The value of J for a given coupling is constant, regardless of the field
strength or operating frequency of the instrument
• Coupling between nuclei of the same type
is referred to as homonuclear coupling
• Coupling between dissimilar nuclei is
referred to as heteronuclear coupling
• The magnitude of this effect is dependent
on the number of bonds intervening between
two nuclei – in general it is a distance effect, where one-bond couplings
would be the strongest
Advanced Spin-spin Coupling
February 28, 2016 128M.M.C.P.
129. NMR Spectroscopy
Con….
There are many variations of the subscripts and superscripts associated with J
constants
In general, the superscript numeral to the left of J is the number of intervening
bonds through which the coupling is taking place
3
J is a coupling constant operating through three bonds
Subscripts to the right of J can be used to show the type of coupling, such as HH for
homonuclear between protons or HC for heteronuclear between a carbon and
proton
Often, this subscript will be used to define the various J-constants within a
complex multiplet: J1, J2, J3, etc. or JAB, JBC, JAC]
Although J values are referred to as positive numbers, they may in actuality be
positive or negative
Advanced Spin-spin Coupling
February 28, 2016 129M.M.C.P.
130. NMR Spectroscopy
MECHANISM OF COUPLING
• The most coherent theory of how spin information is transferred from one
nucleus to another is the Dirac vector model
• In this model, there is an energetic relationship between the spin of the
electrons and the spin of the nuclei
• An electron near the nucleus has the lowest energy of interaction if its spin is
opposite to that of the nucleus
Advanced Spin-spin Coupling
Nuclear spin electron spin
Energy
Nuclear spin electron spin
February 28, 2016 130M.M.C.P.
131. NMR Spectroscopy
MECHANISM OF COUPLING – ONE BOND COUPLINGS, 1
J
• Here, a single bond (two electrons) joins two spin-active nuclei – such as 13
C-
1
H
• The bonding electrons will tend to avoid one another, if one is near the 13
C
nucleus the other will be near the 1
H nucleus
• By the Pauli principle, these electrons must be opposite in spin
• The Dirac model then predicts that the most stable condition between the two
nuclei must be one in which they too are opposite in spin:
Advanced Spin-spin Coupling
13
C spin 1
H spin
electrons opposite in spin
February 28, 2016 131M.M.C.P.
132. NMR Spectroscopy
MECHANISM OF COUPLING – ONE BOND COUPLINGS, 1
J
• These alignments can be used for any heteronuclear pair of spin-active nuclei –
13
P-13
C, etc.
• When two nuclei prefer an opposed alignment, as in this example, the J is
positive
• If the two nuclei have parallel spins, the J will be negative (remember spin
information is transferred through the electrons!)
Advanced Spin-spin Coupling
February 28, 2016 132M.M.C.P.
133. NMR Spectroscopy
MECHANISM OF COUPLING – ONE BOND COUPLINGS, 1
J
• The Dirac model predicts the observed spin-spin coupling for the methine 13
C-
1
H system
• It is important to note that the electron spins must be opposite
Advanced Spin-spin Coupling
13
C
1
H
13
C nuclear resonance
13
C
1
H
Dirac model
favored ground
state
13
C
1
H
13
C
1
H
Dirac model
less-favored
ground state
Excited state is
of lower energy
February 28, 2016 133M.M.C.P.
134. NMR Spectroscopy
MECHANISM OF COUPLING – ONE BOND COUPLINGS, 1
J
• It is these two upper energy states, and the two DEs that generated them that
result in the doublet for an undecoupled methine in a 13
C spectrum
Advanced Spin-spin Coupling
13
C
1
H
13
C
1
H
13
C
1
H
13
C
1
H
February 28, 2016 134M.M.C.P.
135. NMR Spectroscopy
MECHANISM OF COUPLING – TWO BOND COUPLINGS, 2
J
• As the bond angle H-C-H decreases, the amount of electronic interaction
between the two orbitals increases, the electronic spin correlations also
increase, and J becomes larger. They are sometimes called geminal coupling,
because the two nuclei that interact are attached to the same central
atom(Latin gemini = “twins”)
Advanced Spin-spin Coupling
H
H
H-C-H 109o
2JHH = 12-18 Hz
H
H
H-C-H 118o
2JHH = 5 Hz
H
H
H-C-H 120o
2JHH = 0-3 Hz
In general:
JHH
90 100 110 120
40
20
February 28, 2016 135M.M.C.P.
136. NMR Spectroscopy
MECHANISM OF COUPLING – TWO BOND COUPLINGS, 2
J
• Variations in J also result from ring size
• As ring size decreases, the C-C-C bond angle decreases,
the resulting H-C-H bond angle increases, – J becomes
smaller
Advanced Spin-spin Coupling
H
H
H
H
H
H H
H
H
H
C
H
H
2
JHH (Hz) = 3 5 9 11 13 9 to 15
February 28, 2016 136M.M.C.P.
137. NMR Spectroscopy
MECHANISM OF COUPLING – THREE BOND COUPLINGS, 3
J
• These couplings are the one most common to introductory studies in NMR, and are
observed as the coupling through a C-C bond between two C-H bonds - vicinal
coupling.
• Observe the two possible spin intra C-C cations:
Advanced Spin-spin Coupling
February 28, 2016 137M.M.C.P.
+1/2
+1/2
+1/2
-1/2
138. NMR SpectroscopyAdvanced Spin-spin Coupling
0o
dihedral angle
MECHANISM OF COUPLING – THREE BOND COUPLINGS, 3
J
Observe that the orbitals must overlap for this communication to take place
The magnitude of the interaction, it can readily be observed, is greatest when the
orbitals are at angles of 0o
and 180o
to one another:
0o
dihedral angle 180o
dihedral angle
February 28, 2016 138M.M.C.P.
Maximum overlap
139. NMR SpectroscopyAdvanced Spin-spin Coupling
MECHANISM OF COUPLING – THREE BOND COUPLINGS, 3
J
8. Examples of this effect in operation:
3
Jdiaxial = 10-14 Hz
α= 180ο
H
H
H H
3
Jdiequitorial = 4-5 Hz
α= 60ο
H
H
3
Jaxial-eq. = 4-5 Hz
α= 60ο
February 28, 2016 139M.M.C.P.
140. NMR Spectroscopy
MECHANISM OF COUPLING – LONG RANGE COUPLINGS, ≥4
J
• the greater the number of intervening bonds the greater the reduction in opportunity
for orbital overlap – long range couplings are uncommon
• In cases where a rigid structural feature preserves these overlaps, however, long
range couplings are observed
Advanced Spin-spin Coupling
February 28, 2016 140M.M.C.P.
141. NMR Spectroscopy
MECHANISM OF COUPLING – LONG RANGE COUPLINGS, ≥4
J
• Examples include the meta- and para- protons to the observed proton on an
aromatic ring and acetylenic systems:
Advanced Spin-spin Coupling
H
H
C C C C
H H
5
J = 0-1 Jz Hz 3
J = 7-10 Hz 4
J = 1-3 Hz 5
J = 0-1 Hz
H
H
February 28, 2016 141M.M.C.P.
H
H
ortho meta para
142. NMR Spectroscopy
MECHANISM OF COUPLING – LONG RANGE COUPLINGS, ≥4
J
• Rigid aliphatic ring systems exhibit a specialized case of long range coupling – W-
coupling – 4
JW
• The more heavily strained the ring system, the less “flexing” can occur, and the
ability to transmit spin information is preserved
Advanced Spin-spin Coupling
H H O
H
H HH
4
J = 0-1 4
J = 3 4
J = 7 Hz
February 28, 2016 142M.M.C.P.
143. SPIN DECOUPLING
• It is a powerful tool for simplifying a spectrum & is of great value to
organic chemists working with complex molecules. It helps in the
identification of coupled protons in spectra that are too complex for
detailed analysis.
• This technique involves the irradiation of a proton or a group of
equivalent proton with sufficiently intense radio frequency energy to
eliminate completely the observed coupling of the neighboring
protons.
• The simplification of the complex spectrum for easy interpretation is
done by,
1) By using an instrument with a more powerful homogeneous
magnetic field, e.g. a 100 MHz instrument in preference to 60
MHz
instruments.
2) By spin- spin decoupling techniques.
February 28, 2016 143M.M.C.P.
144. ISOTOPE EXCHANGE
• Deuterium (2H or D ), the heavy isotope of hydrogen, has been used
extensively in proton NMR spectroscopy for two reasones. First it is
easily introduced into a molecule. Second, the presence of deuterium in a
molecule is not detected in the proton NMR spectrum.
• Deuterium has a much smaller magnetic dipole moment than hydrogen &
therefore, it absorbs at different field strengths. In case of ethylbromide
the deuterium replaces the methyl hydrogens & the following changes
occurs.
Br-CH2-CH3
Br-CH2-CH2D
Br-CH2-CHD2
Br-CH2-CD3
2H 3H
2H
2H
2H
1H
2H
February 28, 2016 144M.M.C.P.
145. SHIFT REAGENTS
• Lanthanide series of elements are used as shift reagents. A lanthanide ion
can increase its co-ordination number by interacting with unshared electrons.
As a result the NMR spectrum of the comp. that contains a group
possessing unshared pair of electron undergoes change & large chemical
shift as a difference in peaks is observed.
• All the shift reagents are mild Lewis acids. Shift reagent separates NMR
signals those normally overlap. Thus it gives more simplified spectrum.
• Shift reagent are paramagnetic, so large chemical shift take place.
• Shift reagents is normally used in non polar solvents like CdCl3, CCl4 etc.
• Shift reagents, provide a useful technique for spreading out proton NMR
absorption patterns which normally overlap, without increasing the strength
of the applied magnetic field.
February 28, 2016 145M.M.C.P.
146. • In the proton NMR spectrum of n – hexanol, the
high field triplet is distorted which represents the
absorption of a methyl group adjacent to a - CH2 –
group. The low field broad multiplet is due to the
methylene group adjacent to the hydroxyl group.
The proton of the remaining methylene groups are
all burried in the methylene envelope between δ
1.2 & 1.8 .
February 28, 2016 146M.M.C.P.
147. • When the same spectrum is recorded after addition of a
soluble europium (III) complex, that is the shift reagent , the
spectrum is spread out over a wider range of frequencies. So
that it is now simplified almost to first order. In the spectrum
OH absorption signal is shifted too far to be.
February 28, 2016 147M.M.C.P.
148. COMPARISIONS BETWEEN 13C-NMR & 1H-NMR
13C-NMR 1H-NMR
1. Pulse Fourier Technique is used 1. Continuous wave method is followed.
2. Very fast. 2. Slow process.
3. No peak overlapping observed 3. Peak overlapping observed in case of
in the spectrum. complex samples.
4. Sweep generator & sweep coil 4. Required.
are not required in the NMR
instrument.
5. Chemical shift range is wide 5. δ range is very narrow (δ 0-15).
(δ 0-200).
6. Wide band RF is applied rather 6. Tuned to one frequency.
than tuned to a precise frequency.
7. Work on frequency sweep 7. Works on either field sweep
technique. or frequency sweep techniques.
149. February 28, 2016 M.M.C.P. 149
QUESTIONS :-
2o marks:-
1. (a) Explain the basic principles involved in NMR spectroscopy.
(b) Write an account of NMR spectra. How its interpretation ? Explain
with examples. (Sep’07)(Apr’08).
1o marks:-
1. Write a note on splitting of signals in NMR spectra. (May’10).
2. Briefly indicate the functions of various units of NMR spectrometer. (Apr’08).
3. Explain shielding & deshielding effect in NMR spectroscopy. (Apr’08).
4. What is chemical shift ? Explain the factors affecting chemical shift. (Apr’08).
150. February 28, 2016 M.M.C.P. 150
5 marks:-
1. Explain chemical shifts in NMR. (‘03)
2. Explain advantages and applications of FT NMR. (‘97)
Con….
151. REFERENCES :-
1. Sharma YR. Elementary organic spectroscopy principles and
chemical applications. 1st
ed. S. Chand and Company ltd; New
Delhi :2008.
2. Chatwal GR, Anand SK. Instrumental methods of chemical
analysis. 1st
ed. Himalaya Publishing house; Mumbai: 2004.
3. Jag Mohan. Organic spectroscopy principles and applications. 1st
ed. Narosa publishing House; New Delhi: 2001.
4. Sharma BK. Instrumental methods of chemical analysis. 24th
ed.
Goel Publishing house; Meerut: 2005.
5. S. Ravi Shankar. Text book of pharmaceutical analysis. 3rd
ed. Rx
publication; Tirunelveli: 2006.
February 28, 2016 151M.M.C.P.
152. 6. O.V.K. Reddy. Pharmaceutical analysis. Pulse publication;
Hyderabad.
7. Willey. Handbook of spectroscopy. 2003.
8. Pavia, Lampman, Kriz. Introduction of spectroscopy. 3ed
edition.
9. Skoog DA, West DM. principle of instrumental analysis. 2ed
edition.
10.Willard HH, Merritt LL, Dean JA, Settle FA. Instrumental
methods of analysis. Jr CBS publishing and distributors, 7 th
edition.
11. Kasture AV, Mahadik KR, More HN, Wadodkar SG.
Pharmaceutical analysis. Nirali Prakashan. 17th
edition 2008.
February 28, 2016 152M.M.C.P.
153. 12. Silverstein R.M, Webmaster F.A, Spectrometric identification of
organic compounds, 6th
edition.148-150.
13. Kemp W. organic spectroscopy. 3rd
edition.1996.
14. www.google.co.in
February 28, 2016 153M.M.C.P.