This document discusses electronic spectroscopy techniques such as ultraviolet-visible (UV-vis) spectroscopy and chiroptical spectroscopy. It describes how UV-vis spectroscopy can be used to study electronic transitions in molecules, detect functional groups, and perform quantitative analysis. Chiroptical spectroscopy techniques like circular dichroism and optical rotary dispersion are used to determine stereochemistry by measuring differences in absorption of left and right circularly polarized light. Selection rules and origins of electronic transitions are also summarized.
This document discusses electronic spectroscopy techniques such as ultraviolet-visible (UV-vis) spectroscopy and circular dichroism (CD) spectroscopy. It provides details on:
1) How UV-vis and CD spectroscopy work by measuring absorption of photons causing electronic transitions between molecular orbitals.
2) The Beer-Lambert law which relates absorbance to concentration and path length.
3) Factors that determine absorption spectra including chromophores, solvent effects, the Frank-Condon principle, and electronic selection rules.
4) Applications of these techniques in structure determination and quantitative analysis of compounds.
UV/visible spectroscopy involves using electromagnetic radiation in the UV and visible light range to analyze samples. Key principles are that different functional groups and molecular structures absorb radiation at characteristic wavelengths. Absorption of light causes electronic transitions between molecular orbitals. The Beer-Lambert law states that absorbance is directly proportional to concentration, with molar absorptivity coefficients describing this relationship. Absorption spectra provide information to identify compounds and determine concentrations.
Uv visible spectroscopy with InstrumentationSHIVANEE VYAS
Spectroscopy is the study of interaction of electromagnetic radiation with matter. It involves measuring the spectrum (absorption or emission) of a sample when it interacts with electromagnetic radiation such as visible light, UV light, or infrared light. The main types of spectroscopy are absorption spectroscopy and emission spectroscopy. UV-visible spectroscopy measures absorption of ultraviolet and visible light by a substance in solution. It follows Beer-Lambert law where absorbance is directly proportional to concentration and path length of light through the sample. Electronic transitions that occur when absorbing UV-visible light include σ→σ*, n→π*, π→π*, etc. Factors like auxochromes, conjugation, and solvents can cause shifts in the absorption maximum
This document discusses spectroscopy techniques, specifically atomic absorption spectroscopy (AAS). It begins by explaining the electromagnetic spectrum and photon interactions with matter. It then describes different types of spectroscopy including absorption, fluorescence, and phosphorescence. Beer-Lambert law is introduced which states that absorbance is directly proportional to concentration. Instrumental components of a spectrophotometer such as light sources, monochromators, sample holders, and detectors are outlined. The principles of atomic absorption spectroscopy are explained including hollow cathode lamps and atomic excitation. Advantages of AAS compared to atomic emission spectroscopy are provided.
Spectroscopic techniques involve measuring the interaction of electromagnetic radiation with matter. There are various types of spectroscopy depending on the type of radiation used. Infrared (IR) spectroscopy analyzes infrared light interacting with molecules and is based on absorption spectroscopy. IR spectroscopy is useful for qualitative and quantitative analysis, detecting impurities, and characterizing organic compounds. Molecular vibrations that can be analyzed include stretching vibrations, which change bond lengths, and bending vibrations, which change bond angles. Selection rules determine which vibrations are IR active based on whether they induce a change in the molecule's dipole moment.
This document provides an overview of UV/Visible spectroscopy. It discusses the basic principles including electromagnetic radiation, electronic transitions, instrumentation, and applications. The key points are:
- UV/Visible spectroscopy analyzes absorption of electromagnetic radiation in the UV and visible light range by molecules undergoing electronic transitions.
- Instrumentation includes a radiation source, monochromator to select wavelengths, sample and reference cells, detectors to measure light intensity, and a recorder to generate spectra.
- Electronic transitions involved are σ→σ*, n→π*, π→π*, which determine the wavelengths absorbed and spectra obtained for different functional groups.
UV/visible spectroscopy involves using electromagnetic radiation in the UV and visible light range to analyze samples. Absorption of this radiation causes electronic transitions between molecular energy levels. The wavelength and intensity of absorption peaks provide information about functional groups in molecules. Factors like conjugation and substituents can cause bathochromic, hypsochromic, hyperchromic, or hypochromic shifts in absorption maxima and intensity. UV/visible spectroscopy has applications in qualitative and quantitative analysis, detection of impurities, and determination of molecular properties.
The document discusses UV-visible spectroscopy, which involves measuring the absorption of ultraviolet or visible radiation by molecules as they transition between energy levels. It explains the basic concepts of spectroscopy including electromagnetic radiation, absorption curves, electronic transitions, and Beer's and Lambert's laws which describe the relationship between absorbance and analyte concentration. The principles of UV-visible spectroscopy are useful for qualitative and quantitative analysis of compounds in various applications.
This document discusses electronic spectroscopy techniques such as ultraviolet-visible (UV-vis) spectroscopy and circular dichroism (CD) spectroscopy. It provides details on:
1) How UV-vis and CD spectroscopy work by measuring absorption of photons causing electronic transitions between molecular orbitals.
2) The Beer-Lambert law which relates absorbance to concentration and path length.
3) Factors that determine absorption spectra including chromophores, solvent effects, the Frank-Condon principle, and electronic selection rules.
4) Applications of these techniques in structure determination and quantitative analysis of compounds.
UV/visible spectroscopy involves using electromagnetic radiation in the UV and visible light range to analyze samples. Key principles are that different functional groups and molecular structures absorb radiation at characteristic wavelengths. Absorption of light causes electronic transitions between molecular orbitals. The Beer-Lambert law states that absorbance is directly proportional to concentration, with molar absorptivity coefficients describing this relationship. Absorption spectra provide information to identify compounds and determine concentrations.
Uv visible spectroscopy with InstrumentationSHIVANEE VYAS
Spectroscopy is the study of interaction of electromagnetic radiation with matter. It involves measuring the spectrum (absorption or emission) of a sample when it interacts with electromagnetic radiation such as visible light, UV light, or infrared light. The main types of spectroscopy are absorption spectroscopy and emission spectroscopy. UV-visible spectroscopy measures absorption of ultraviolet and visible light by a substance in solution. It follows Beer-Lambert law where absorbance is directly proportional to concentration and path length of light through the sample. Electronic transitions that occur when absorbing UV-visible light include σ→σ*, n→π*, π→π*, etc. Factors like auxochromes, conjugation, and solvents can cause shifts in the absorption maximum
This document discusses spectroscopy techniques, specifically atomic absorption spectroscopy (AAS). It begins by explaining the electromagnetic spectrum and photon interactions with matter. It then describes different types of spectroscopy including absorption, fluorescence, and phosphorescence. Beer-Lambert law is introduced which states that absorbance is directly proportional to concentration. Instrumental components of a spectrophotometer such as light sources, monochromators, sample holders, and detectors are outlined. The principles of atomic absorption spectroscopy are explained including hollow cathode lamps and atomic excitation. Advantages of AAS compared to atomic emission spectroscopy are provided.
Spectroscopic techniques involve measuring the interaction of electromagnetic radiation with matter. There are various types of spectroscopy depending on the type of radiation used. Infrared (IR) spectroscopy analyzes infrared light interacting with molecules and is based on absorption spectroscopy. IR spectroscopy is useful for qualitative and quantitative analysis, detecting impurities, and characterizing organic compounds. Molecular vibrations that can be analyzed include stretching vibrations, which change bond lengths, and bending vibrations, which change bond angles. Selection rules determine which vibrations are IR active based on whether they induce a change in the molecule's dipole moment.
This document provides an overview of UV/Visible spectroscopy. It discusses the basic principles including electromagnetic radiation, electronic transitions, instrumentation, and applications. The key points are:
- UV/Visible spectroscopy analyzes absorption of electromagnetic radiation in the UV and visible light range by molecules undergoing electronic transitions.
- Instrumentation includes a radiation source, monochromator to select wavelengths, sample and reference cells, detectors to measure light intensity, and a recorder to generate spectra.
- Electronic transitions involved are σ→σ*, n→π*, π→π*, which determine the wavelengths absorbed and spectra obtained for different functional groups.
UV/visible spectroscopy involves using electromagnetic radiation in the UV and visible light range to analyze samples. Absorption of this radiation causes electronic transitions between molecular energy levels. The wavelength and intensity of absorption peaks provide information about functional groups in molecules. Factors like conjugation and substituents can cause bathochromic, hypsochromic, hyperchromic, or hypochromic shifts in absorption maxima and intensity. UV/visible spectroscopy has applications in qualitative and quantitative analysis, detection of impurities, and determination of molecular properties.
The document discusses UV-visible spectroscopy, which involves measuring the absorption of ultraviolet or visible radiation by molecules as they transition between energy levels. It explains the basic concepts of spectroscopy including electromagnetic radiation, absorption curves, electronic transitions, and Beer's and Lambert's laws which describe the relationship between absorbance and analyte concentration. The principles of UV-visible spectroscopy are useful for qualitative and quantitative analysis of compounds in various applications.
UV/visible spectroscopy involves the interaction of electromagnetic radiation in the ultraviolet-visible spectral region with matter. It works based on electronic transitions in molecules that absorb UV-visible light. The absorbed wavelengths are characteristic of the chemical bonds in a substance. Beer's law states that absorbance is directly proportional to concentration, allowing for quantitative analysis. Chromophores are functional groups that absorb UV-visible light, while auxochromes modify the absorption properties. Shifts in absorption maximum wavelength or intensity can provide information about molecular structure. Applications include qualitative and quantitative analysis of organic compounds.
Spectroscopy is the branch of science that deals with the study of interaction of electromagnetic radiation with matter. It uses electromagnetic radiation in the ultraviolet-visible region. When this radiation interacts with molecules, electronic transitions between different energy levels can occur. The wavelength and intensity of absorbed light depends on characteristics of the molecule such as its structure and functional groups. Spectroscopy can be used to identify unknown compounds, determine molecular structure, and calculate concentration through the Beer-Lambert law.
This document provides an overview of UV/Visible spectroscopy. It discusses electromagnetic radiation, electronic transitions that can occur when molecules absorb UV-Visible light, and the principles of spectroscopy including Lambert's law and Beer's law. It describes factors that can cause shifts in absorption maximum wavelengths and intensities, such as auxochromes, solvents, conjugation, and pH. Finally, it lists some applications of UV-Vis spectroscopy like qualitative and quantitative analysis, detection of impurities and isomers, and determination of molecular weight.
This document discusses ultraviolet-visible (UV-vis) spectroscopy, chiroptical spectroscopy, and the origin of electronic spectra. It explains that UV-vis spectroscopy involves the absorption of photons by molecules, causing electronic transitions from ground state to excited states. Chiroptical spectroscopy measures the difference in absorption of left and right circularly polarized light. Electronic transitions in UV-vis spectroscopy originate from valence electrons in chromophores being promoted to higher energy levels. Spectra are displayed with wavelength on the x-axis and absorbance, molar absorptivity, or molar ellipticity on the y-axis.
UV/visible spectroscopy involves measuring the absorption of ultraviolet or visible light by molecules. It utilizes light in the wavelength range of 200-800 nm.
The key components of a UV-visible spectrophotometer are a light source, wavelength selector such as a monochromator, sample holder, detector, and associated electronics. Common light sources include deuterium lamps, tungsten lamps, and mercury lamps. Samples are typically held in quartz or glass cuvettes. Detectors include phototubes and photodiodes.
UV-visible spectroscopy can be used to analyze samples containing multiple components. Methods for multicomponent analysis include simultaneous equations using absorption data at two wavelengths, absorbance ratio methods
This document provides an overview of molecular spectroscopy, with a focus on visible and ultraviolet spectroscopy. It describes the electromagnetic spectrum and different types of molecular transitions. UV-Vis spectroscopy involves electronic transitions between molecular orbitals that are excited by photons in the UV-Vis range. The document discusses instrumentation for UV-Vis spectroscopy including light sources, monochromators, detectors, and single and double beam spectrometers. It also covers quantitative analysis using Beer's Law and limitations to Beer's Law. Applications of UV-Vis spectroscopy include structure determination and quantitative analysis of absorbing species containing p, s, and n electrons.
Ultraviolet and visible (UV-Vis) absorption spectroscopy measures the attenuation of light passing through or reflected from a sample. When light energy matches an electronic transition in a molecule, some light is absorbed, promoting electrons to higher orbitals. The resulting absorbance spectrum shows absorbance versus wavelength. Fluorescence spectroscopy involves excitation of molecules to higher electronic singlet states followed by emission of light as they relax to ground states. Quantum yield is the ratio of emitted to absorbed photons. Both techniques are useful in characterizing biological systems like proteins, DNA, and fluorophores.
This document provides information about spectroscopy. It defines spectroscopy as the study of interaction of electromagnetic radiation with matter. It discusses the basic principles of UV-visible spectroscopy and infrared spectroscopy. UV-visible spectroscopy involves absorption of radiation in the visible and UV region, causing electrons to move between energy levels. Infrared spectroscopy analyzes absorption in the infrared region to determine molecular structure based on vibrational and rotational transitions. The document also defines key terms used in spectroscopy like chromophore, auxochrome, and discusses different types of shifts that can occur in absorption spectra.
This document provides information about spectroscopy. It defines spectroscopy as the study of interaction of electromagnetic radiation with matter. It discusses the different types of electromagnetic radiation including ultraviolet-visible spectroscopy, infrared spectroscopy, and mass spectroscopy. It focuses on ultraviolet-visible spectroscopy, explaining that it involves electronic transitions when molecules absorb ultraviolet or visible light. It describes factors that affect absorption spectra such as chromophores, auxochromes, and solvents. It also defines terms used in ultraviolet-visible spectroscopy and discusses the types of shifts and effects that can occur in absorption spectra.
This document provides information about spectroscopy. It defines spectroscopy as the study of interaction of electromagnetic radiation with matter. It discusses the different types of electromagnetic radiation including ultraviolet-visible spectroscopy, infrared spectroscopy, and mass spectroscopy. It focuses on defining key terms related to spectroscopy such as chromophores, auxochromes, and the different types of electronic transitions that can occur. It also describes concepts such as bathochromic shifts, hypsochromic shifts, and how auxochromes can cause hyperchromic or hypochromic effects.
1. UV-Vis spectroscopy detects electronic transitions in molecules when photons are absorbed, promoting electrons to higher energy states. Transitions involve π or n electrons and occur in the 200-700nm region.
2. Absorption depends on functional groups called chromophores as well as conjugation, solvent effects, and molecular structure. Selection rules govern allowed transitions.
3. Spectra appear as bands representing many overlapping transitions between vibrational/rotational energy levels of ground and excited electronic states. Band features provide structural information.
This document provides an overview of UV spectroscopy. It discusses electronic transitions that can be observed via UV spectroscopy, including n→π*, π→π*, n→s*, and s→s* transitions. The energy required for different transitions is discussed, with n→π* requiring the lowest energy. Selection rules and factors that influence the observation of transitions are also covered. The document introduces concepts like chromophores, auxochromes, and how they can shift absorption bands.
UV-Visible Spectroscopy involves the interaction of electromagnetic radiation in the ultraviolet and visible spectral regions with matter. When molecules absorb this radiation, electrons are excited from one energy level to a higher level. This causes absorption bands to appear in the absorption spectrum. Beer's law states that absorbance is directly proportional to concentration and path length. Chromophores are groups that absorb radiation, while auxochromes shift absorption to longer wavelengths by extending conjugation. Spectroscopy has applications in quantitative analysis, qualitative analysis, detection of functional groups and impurities, and determination of properties like extent of conjugation.
This document provides an overview of UV-Visible spectroscopy. It discusses how UV radiation causes electronic transitions in molecules, which can be observed via absorption spectroscopy. The instrumentation used includes sources of UV and visible light, a monochromator to select wavelengths, and a detector. Samples are dissolved and placed in transparent cuvettes for analysis. Spectra are recorded as absorbances and show absorption bands corresponding to electronic transitions. UV-Vis is useful for structure elucidation and quantitative analysis.
UV spectroscopy is an analytical method used to detct the numbers of double and triple bonds present in dienes ,trienes and polyenes compounds.The energy corresponds to EM radiation in the ultraviolet (UV) region, 100-350 nm, and visible (VIS) regions 350-700 nm of the spectrum is known as UV spectrum.
This document provides an overview of molecular spectroscopy. It discusses Maxwell's theory of electromagnetic radiation and how spectroscopy can be divided into absorption and emission types. Key concepts in UV-visible spectroscopy are explained, including Lambert Beer's law, electronic transitions between orbitals, and factors that influence absorption maxima wavelengths. The document also covers infrared spectroscopy, discussing active and inactive molecular vibrations, different types of vibrations, and the fingerprint region.
UV-visible spectroscopy is a technique that uses light in the visible and adjacent ranges. It works by measuring how much light is absorbed by a sample at each wavelength. There are several types of electronic transitions that can occur when molecules absorb this light. The amount of light absorbed follows Beer's law and is proportional to the concentration and path length of the sample. A UV-visible spectrophotometer consists of a light source, monochromator, sample holder, detector, and recording device. This technique has many applications including detection of impurities, structure elucidation, and quantitative analysis in pharmaceutical analysis.
Spectroscopy is the study of the interaction of electromagnetic radiation with matter. There are different types of electromagnetic waves that make up the electromagnetic spectrum, including gamma rays, x-rays, ultraviolet light, visible light, infrared radiation, and radio waves. Spectroscopy techniques take advantage of the fact that molecules absorb specific wavelengths of light depending on their structure. Absorption spectra provide information about molecular structure through relationships between absorption wavelengths and transitions between molecular energy levels.
UV/Visible spectroscopy involves the interaction of electromagnetic radiation in the ultraviolet-visible spectral region with matter. Key points:
1. Electromagnetic radiation consists of photons that interact with molecules through electronic, vibrational, and rotational energy transitions.
2. UV/Vis spectroscopy follows Beer's law - absorbance is directly proportional to concentration and path length. It can be used to determine concentrations.
3. Chromophores are functional groups that absorb UV-Vis radiation through n→π* and π→π* transitions. Common chromophores include C=O, C=C, C≡N.
4. Auxochromes are functional groups that modify the absorption properties of chromoph
This document provides an overview of a university course on organic synthesis. It covers topics like pericyclic reactions, electrocyclizations, sigmatropic rearrangements, and the Woodward-Hoffmann rules for predicting stereochemistry. Examples are given of reaction mechanisms and how the rules explain stereochemical outcomes. The document also lists additional reading materials and notes that attending all lectures is essential since not all material is covered in the handout.
Grignard reagents react with carbonyl compounds like formaldehyde, aldehydes, ketones, and esters to form alcohols. The type of alcohol produced depends on the carbonyl compound. Formaldehyde yields primary alcohols, aldehydes yield secondary alcohols, ketones yield tertiary alcohols, and esters can yield tertiary alcohols after dissociation. Organolithium reagents react similarly to Grignard reagents. Sodium salts of acetylenes also react to form acetylenic alcohols. Retrosynthetic analysis involves disconnecting the carbon bearing the hydroxyl group to reveal possible reactants.
UV/visible spectroscopy involves the interaction of electromagnetic radiation in the ultraviolet-visible spectral region with matter. It works based on electronic transitions in molecules that absorb UV-visible light. The absorbed wavelengths are characteristic of the chemical bonds in a substance. Beer's law states that absorbance is directly proportional to concentration, allowing for quantitative analysis. Chromophores are functional groups that absorb UV-visible light, while auxochromes modify the absorption properties. Shifts in absorption maximum wavelength or intensity can provide information about molecular structure. Applications include qualitative and quantitative analysis of organic compounds.
Spectroscopy is the branch of science that deals with the study of interaction of electromagnetic radiation with matter. It uses electromagnetic radiation in the ultraviolet-visible region. When this radiation interacts with molecules, electronic transitions between different energy levels can occur. The wavelength and intensity of absorbed light depends on characteristics of the molecule such as its structure and functional groups. Spectroscopy can be used to identify unknown compounds, determine molecular structure, and calculate concentration through the Beer-Lambert law.
This document provides an overview of UV/Visible spectroscopy. It discusses electromagnetic radiation, electronic transitions that can occur when molecules absorb UV-Visible light, and the principles of spectroscopy including Lambert's law and Beer's law. It describes factors that can cause shifts in absorption maximum wavelengths and intensities, such as auxochromes, solvents, conjugation, and pH. Finally, it lists some applications of UV-Vis spectroscopy like qualitative and quantitative analysis, detection of impurities and isomers, and determination of molecular weight.
This document discusses ultraviolet-visible (UV-vis) spectroscopy, chiroptical spectroscopy, and the origin of electronic spectra. It explains that UV-vis spectroscopy involves the absorption of photons by molecules, causing electronic transitions from ground state to excited states. Chiroptical spectroscopy measures the difference in absorption of left and right circularly polarized light. Electronic transitions in UV-vis spectroscopy originate from valence electrons in chromophores being promoted to higher energy levels. Spectra are displayed with wavelength on the x-axis and absorbance, molar absorptivity, or molar ellipticity on the y-axis.
UV/visible spectroscopy involves measuring the absorption of ultraviolet or visible light by molecules. It utilizes light in the wavelength range of 200-800 nm.
The key components of a UV-visible spectrophotometer are a light source, wavelength selector such as a monochromator, sample holder, detector, and associated electronics. Common light sources include deuterium lamps, tungsten lamps, and mercury lamps. Samples are typically held in quartz or glass cuvettes. Detectors include phototubes and photodiodes.
UV-visible spectroscopy can be used to analyze samples containing multiple components. Methods for multicomponent analysis include simultaneous equations using absorption data at two wavelengths, absorbance ratio methods
This document provides an overview of molecular spectroscopy, with a focus on visible and ultraviolet spectroscopy. It describes the electromagnetic spectrum and different types of molecular transitions. UV-Vis spectroscopy involves electronic transitions between molecular orbitals that are excited by photons in the UV-Vis range. The document discusses instrumentation for UV-Vis spectroscopy including light sources, monochromators, detectors, and single and double beam spectrometers. It also covers quantitative analysis using Beer's Law and limitations to Beer's Law. Applications of UV-Vis spectroscopy include structure determination and quantitative analysis of absorbing species containing p, s, and n electrons.
Ultraviolet and visible (UV-Vis) absorption spectroscopy measures the attenuation of light passing through or reflected from a sample. When light energy matches an electronic transition in a molecule, some light is absorbed, promoting electrons to higher orbitals. The resulting absorbance spectrum shows absorbance versus wavelength. Fluorescence spectroscopy involves excitation of molecules to higher electronic singlet states followed by emission of light as they relax to ground states. Quantum yield is the ratio of emitted to absorbed photons. Both techniques are useful in characterizing biological systems like proteins, DNA, and fluorophores.
This document provides information about spectroscopy. It defines spectroscopy as the study of interaction of electromagnetic radiation with matter. It discusses the basic principles of UV-visible spectroscopy and infrared spectroscopy. UV-visible spectroscopy involves absorption of radiation in the visible and UV region, causing electrons to move between energy levels. Infrared spectroscopy analyzes absorption in the infrared region to determine molecular structure based on vibrational and rotational transitions. The document also defines key terms used in spectroscopy like chromophore, auxochrome, and discusses different types of shifts that can occur in absorption spectra.
This document provides information about spectroscopy. It defines spectroscopy as the study of interaction of electromagnetic radiation with matter. It discusses the different types of electromagnetic radiation including ultraviolet-visible spectroscopy, infrared spectroscopy, and mass spectroscopy. It focuses on ultraviolet-visible spectroscopy, explaining that it involves electronic transitions when molecules absorb ultraviolet or visible light. It describes factors that affect absorption spectra such as chromophores, auxochromes, and solvents. It also defines terms used in ultraviolet-visible spectroscopy and discusses the types of shifts and effects that can occur in absorption spectra.
This document provides information about spectroscopy. It defines spectroscopy as the study of interaction of electromagnetic radiation with matter. It discusses the different types of electromagnetic radiation including ultraviolet-visible spectroscopy, infrared spectroscopy, and mass spectroscopy. It focuses on defining key terms related to spectroscopy such as chromophores, auxochromes, and the different types of electronic transitions that can occur. It also describes concepts such as bathochromic shifts, hypsochromic shifts, and how auxochromes can cause hyperchromic or hypochromic effects.
1. UV-Vis spectroscopy detects electronic transitions in molecules when photons are absorbed, promoting electrons to higher energy states. Transitions involve π or n electrons and occur in the 200-700nm region.
2. Absorption depends on functional groups called chromophores as well as conjugation, solvent effects, and molecular structure. Selection rules govern allowed transitions.
3. Spectra appear as bands representing many overlapping transitions between vibrational/rotational energy levels of ground and excited electronic states. Band features provide structural information.
This document provides an overview of UV spectroscopy. It discusses electronic transitions that can be observed via UV spectroscopy, including n→π*, π→π*, n→s*, and s→s* transitions. The energy required for different transitions is discussed, with n→π* requiring the lowest energy. Selection rules and factors that influence the observation of transitions are also covered. The document introduces concepts like chromophores, auxochromes, and how they can shift absorption bands.
UV-Visible Spectroscopy involves the interaction of electromagnetic radiation in the ultraviolet and visible spectral regions with matter. When molecules absorb this radiation, electrons are excited from one energy level to a higher level. This causes absorption bands to appear in the absorption spectrum. Beer's law states that absorbance is directly proportional to concentration and path length. Chromophores are groups that absorb radiation, while auxochromes shift absorption to longer wavelengths by extending conjugation. Spectroscopy has applications in quantitative analysis, qualitative analysis, detection of functional groups and impurities, and determination of properties like extent of conjugation.
This document provides an overview of UV-Visible spectroscopy. It discusses how UV radiation causes electronic transitions in molecules, which can be observed via absorption spectroscopy. The instrumentation used includes sources of UV and visible light, a monochromator to select wavelengths, and a detector. Samples are dissolved and placed in transparent cuvettes for analysis. Spectra are recorded as absorbances and show absorption bands corresponding to electronic transitions. UV-Vis is useful for structure elucidation and quantitative analysis.
UV spectroscopy is an analytical method used to detct the numbers of double and triple bonds present in dienes ,trienes and polyenes compounds.The energy corresponds to EM radiation in the ultraviolet (UV) region, 100-350 nm, and visible (VIS) regions 350-700 nm of the spectrum is known as UV spectrum.
This document provides an overview of molecular spectroscopy. It discusses Maxwell's theory of electromagnetic radiation and how spectroscopy can be divided into absorption and emission types. Key concepts in UV-visible spectroscopy are explained, including Lambert Beer's law, electronic transitions between orbitals, and factors that influence absorption maxima wavelengths. The document also covers infrared spectroscopy, discussing active and inactive molecular vibrations, different types of vibrations, and the fingerprint region.
UV-visible spectroscopy is a technique that uses light in the visible and adjacent ranges. It works by measuring how much light is absorbed by a sample at each wavelength. There are several types of electronic transitions that can occur when molecules absorb this light. The amount of light absorbed follows Beer's law and is proportional to the concentration and path length of the sample. A UV-visible spectrophotometer consists of a light source, monochromator, sample holder, detector, and recording device. This technique has many applications including detection of impurities, structure elucidation, and quantitative analysis in pharmaceutical analysis.
Spectroscopy is the study of the interaction of electromagnetic radiation with matter. There are different types of electromagnetic waves that make up the electromagnetic spectrum, including gamma rays, x-rays, ultraviolet light, visible light, infrared radiation, and radio waves. Spectroscopy techniques take advantage of the fact that molecules absorb specific wavelengths of light depending on their structure. Absorption spectra provide information about molecular structure through relationships between absorption wavelengths and transitions between molecular energy levels.
UV/Visible spectroscopy involves the interaction of electromagnetic radiation in the ultraviolet-visible spectral region with matter. Key points:
1. Electromagnetic radiation consists of photons that interact with molecules through electronic, vibrational, and rotational energy transitions.
2. UV/Vis spectroscopy follows Beer's law - absorbance is directly proportional to concentration and path length. It can be used to determine concentrations.
3. Chromophores are functional groups that absorb UV-Vis radiation through n→π* and π→π* transitions. Common chromophores include C=O, C=C, C≡N.
4. Auxochromes are functional groups that modify the absorption properties of chromoph
This document provides an overview of a university course on organic synthesis. It covers topics like pericyclic reactions, electrocyclizations, sigmatropic rearrangements, and the Woodward-Hoffmann rules for predicting stereochemistry. Examples are given of reaction mechanisms and how the rules explain stereochemical outcomes. The document also lists additional reading materials and notes that attending all lectures is essential since not all material is covered in the handout.
Grignard reagents react with carbonyl compounds like formaldehyde, aldehydes, ketones, and esters to form alcohols. The type of alcohol produced depends on the carbonyl compound. Formaldehyde yields primary alcohols, aldehydes yield secondary alcohols, ketones yield tertiary alcohols, and esters can yield tertiary alcohols after dissociation. Organolithium reagents react similarly to Grignard reagents. Sodium salts of acetylenes also react to form acetylenic alcohols. Retrosynthetic analysis involves disconnecting the carbon bearing the hydroxyl group to reveal possible reactants.
This document provides an overview of infrared spectroscopy. It discusses the instrumentation used, including radiation sources, sample handling techniques for solids, liquids and gases, and various detectors. Fourier transform infrared spectroscopy is also introduced. Applications of infrared spectroscopy discussed include qualitative analysis for structure elucidation of organic compounds, and quantitative analysis using calibration curves and standard addition methods. Limitations and advantages of quantitative infrared methods are outlined.
This document discusses UV-visible spectroscopy. It begins by introducing spectroscopy and the different types, including UV, IR, NMR, and mass spectrometry. It then explains the principles of UV light absorption and Beer-Lambert's law. Factors that affect the position and intensity of UV absorption peaks are described, such as chromophores, auxochromes, pH, solvents, and conjugation. Finally, some applications of UV-visible spectroscopy are mentioned, such as determining molecular weight, impurities, concentrations, and characterizing aromatic compounds.
- Oxidative addition, reductive elimination, migratory insertion, and β-hydrogen elimination are important reactions in organometallic chemistry that involve changes in oxidation states and coordination numbers of metals.
- Oxidative addition involves the addition of ligands to a metal center accompanied by an increase in the metal's oxidation state and coordination number. Reductive elimination is essentially the reverse of this.
- Migratory insertion involves the migration of a ligand from one metal-carbon bond to an adjacent metal-carbon bond, without changing the metal's oxidation state.
- β-hydrogen elimination converts an alkyl ligand with a β-hydrogen into a metal hydride and an alkene ligand.
Polymers are macromolecules formed by the joining of repeating structural units called monomers. They can be classified based on their source as natural, semi-synthetic, or synthetic. Classification based on structure includes linear, branched, and cross-linked polymers. Polymers are also classified based on their molecular forces and applications as elastomers, fibers, thermoplastics, and thermosets. Polymerization can occur by addition or condensation reactions. Common addition polymers include polyethene, Teflon, polyacrylonitrile, Buna-S, natural rubber, neoprene, Buna-N, and polyvinyl chloride. Condensation polymers include polyamides like nylon
Level 3 NCEA - NZ: A Nation In the Making 1872 - 1900 SML.pptHenry Hollis
The History of NZ 1870-1900.
Making of a Nation.
From the NZ Wars to Liberals,
Richard Seddon, George Grey,
Social Laboratory, New Zealand,
Confiscations, Kotahitanga, Kingitanga, Parliament, Suffrage, Repudiation, Economic Change, Agriculture, Gold Mining, Timber, Flax, Sheep, Dairying,
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
In this slide, we'll explore how to set up warehouses and locations in Odoo 17 Inventory. This will help us manage our stock effectively, track inventory levels, and streamline warehouse operations.
This presentation was provided by Racquel Jemison, Ph.D., Christina MacLaughlin, Ph.D., and Paulomi Majumder. Ph.D., all of the American Chemical Society, for the second session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session Two: 'Expanding Pathways to Publishing Careers,' was held June 13, 2024.
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...PECB
Denis is a dynamic and results-driven Chief Information Officer (CIO) with a distinguished career spanning information systems analysis and technical project management. With a proven track record of spearheading the design and delivery of cutting-edge Information Management solutions, he has consistently elevated business operations, streamlined reporting functions, and maximized process efficiency.
Certified as an ISO/IEC 27001: Information Security Management Systems (ISMS) Lead Implementer, Data Protection Officer, and Cyber Risks Analyst, Denis brings a heightened focus on data security, privacy, and cyber resilience to every endeavor.
His expertise extends across a diverse spectrum of reporting, database, and web development applications, underpinned by an exceptional grasp of data storage and virtualization technologies. His proficiency in application testing, database administration, and data cleansing ensures seamless execution of complex projects.
What sets Denis apart is his comprehensive understanding of Business and Systems Analysis technologies, honed through involvement in all phases of the Software Development Lifecycle (SDLC). From meticulous requirements gathering to precise analysis, innovative design, rigorous development, thorough testing, and successful implementation, he has consistently delivered exceptional results.
Throughout his career, he has taken on multifaceted roles, from leading technical project management teams to owning solutions that drive operational excellence. His conscientious and proactive approach is unwavering, whether he is working independently or collaboratively within a team. His ability to connect with colleagues on a personal level underscores his commitment to fostering a harmonious and productive workplace environment.
Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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A Visual Guide to 1 Samuel | A Tale of Two HeartsSteve Thomason
These slides walk through the story of 1 Samuel. Samuel is the last judge of Israel. The people reject God and want a king. Saul is anointed as the first king, but he is not a good king. David, the shepherd boy is anointed and Saul is envious of him. David shows honor while Saul continues to self destruct.
1. Electronic Spectroscopy
• Ultraviolet (UV) and visible (vis) spectroscopy:
• This is the earliest method of molecular
spectroscopy.
• A phenomenon of interaction of molecules with
UV and visible lights.
• Absorption of photon results in electronic
transition of a molecule, and electrons are
promoted from ground state to higher electronic
states.
2. UV and Visible Spectroscopy
• In structure determination : UV-vis spectroscopy is
used to detect the presence of chromophores like dienes,
aromatics, polyenes, and conjugated ketones, etc.
• Also very useful in quantitative analysis of compounds
with chromophores.
• Chiroptical spectroscopy- Optical rotary
dispersion/ORD and Circular dichroism/CD : the
difference in the refraction (ORD) or absorption (CD)
of left and right circularly polarized light is measured,
or absorptivity (CD) between left and right circularly
polarized light .
3. Chiroptical Spectroscopy
• Chiroptical properties reflect stereochemical
arrangement of atom in a molecule. Both
CD and ORD show sense of handedness in
reflecting the handedness of
nonsuperimposable mirror-image molecule
(enantiomer). So their curves appear as
positive or negative peaks of Cotton effects
reflecting the difference in chirality of
molecule.
4. Display of spectra
• Horizontal scale (abscissa): all three methods use
wavelength, λ, in nm (nanometer) unit.
• Vertical scale (ordinate):
• UV-vis: absorbance, A, or molar absorptivity, ε.
• CD: difference in molar absorptivity, Δε, or
molar ellipticity, [θ].
• ORD: molar rotation, [φ].
5. UV: A vs. λ (nm), the same curve for 3R-, 3S-isomer, and racemate.
CD: Δε vs. λ, + Cotton effect for 3R-isomer, and - Cotton effect for
3S-isomer.
ORD: [φ] (molar rotation) vs. λ, + C. E. for 3R-isomer and – C. E.
for 3S-isomer.
6. Origin of electronic spectra
• Absorptions of UV-vis light photons by
molecule results in electronic excitation of
molecule with chromophore.
• The electronic transition involves
promotion of electron from a electronic
ground state to higher energy state, usually
from a molecular orbital called HOMO to
LUMO.
7. Electronic transition
• HOMO: Highest Occupied Molecular
Orbital
• LUMO: Lowest Unoccupied Molecular
Orbital
• Electronic transition usually originates from
valence electrons in a chromophore, such as
the nonbonding (n) or π electrons in
unsaturated functions.
8. Electronic transition
• Can be assigned to different transition types
according to the molecular orbital involved,
such as π -> π* (in alkenes or benzene), n -
>π* (in keto group).
• Due to their symmetry property in MO’s,
such transition can be allowed (high
intensity) or forbidden (low intensity).
• Absorptions with high ε are allowed
transitions, and low ε absorptions are
forbidden transiton.
11. Measurement of UV-vis
absorption
• The electromagnetic radiation may be
described by the wavelength λ (nm), by the
frequency ν (s-1), or by the wavenumber ,
(cm-1), related by energy difference as
following relationships:
12. UV regions
• The UV region is divided to two parts:
• a. the near UV region: 190-400 nm.
b.The far or vacuum UV region: below 190
nm.
The far UV region has interference due to
absorption of oxygen, which must be
removed or flushed with nitrogen in the
spectrometer to obtain the spectra of sample.
13. Measurement of Absorbance
• The absorbance (A) or molar absorptivity (ε)
of an UV band is calculated according to the
Beer-Bouger-Lambert Law:
I0 : the intensity of incident light
I : the intensity of transmitted light
l : the path length in cm
c : the concentration in mol L-1
k : the absorption coefficient
ε : the molar extinction coefficient or molar
absorptivity in cm2 mol-1 or L mol-1 cm-1.
14. Absorbance
• The relationship between k and ε is
• Since absorbance A = , and A is the
actual quantity measured, the following eqn.
relates A with ε:
• For i absorbing species :
• The actual quantity measured is the relative
intensities of the light beam transmitted by a
reference cell containing pure solvent and
an identical cell containing sample solution.
16. Frank-Condon Principle
• The broadened bands of UV curve indicate
wide distribution of energies, due to
superimpostion of several vibrational levels
on the electronic level.
• From the P.E. diagram of a diatomic system,
the G.S. has lower energy, shorter requil.
(bond length), while the E.S. has higher
energy, longer requil. (bond weaker). Each of
this electronic state has many vibrational
states in it.
17. Frank-Condon Principle
• It is the transitions between the lowest
vitrational state (ν = 0) in G.S. to various
vib. levels in E.S. that determine the shape
and intensity of a UV band.
• So it is determined by the spacing of the
vibrational levels and the distribution and
contribution of each vibrational subband to
the total band intensity.
• This is governed by the Frank-Condon
Principle stated as following:
18. Frank-Condon Principle
• “The nuclear motion (10-13 s) is much
slower as compared with electronic motion
in transition (10-16 s), so it is negligible
during the time required for an electronic
excitation.”
• Since the nucleus does not move during the
excitation, the internuclear distance keeps
the same, and “the most probable
component of a electronic transition
involves only the vertical transitions”.
19. Frank-Condon Principle
• The excitation going from ν = 0 (G.S.) to ν
= 3 (E.S.) is the most probable one for
vertical transition because it falls on the
highest point in the electron probability
curve for ν = 3 in E.S.
• Other vertical transitions (0->2, 0->1,...,
0->4, 0->5,...) are smaller in their
probabilities of transition as revealed in the
composite fine struture of vibronic broad
band.
21. Solvent effects
• Promotion of electron from G.S. to E.S. leads to
more polar excited state that is more easily
stabilized by polar solvent associations (H-bonds).
In going from nonpolar to polar solvents the fine
vibronic structure is smoothed into a broad band.
• For π -> π* transition, the π* state is more polar
and stabilized more in polar solvent relative to
nonpolar one, thus in going from nonpolar to polar
solvent there is a red shift or bathochromic shift
(increase in λmax, decrease in ΔE).
22. Solvent effects
• For n -> π* transition, the n state is much
more easily stabilized by polar solvent
effects (H-bonds and association), so in
going from nonpolar to polar solvent there
is a blue shift or hypsochromic shift
(decrease in λmax, increase in ΔE).
25. Electronic transition
• Electronic transition (UV) measure the
probability and energy of exciting a molecule
from G.S. to E.S. (or promoting electron from
HOMO to LUMO).
• For each energy state both singlet (S) and
triplet (T) states are possible. In singlet state
the spins of electron pair are antiparallel; if the
spins are parallel, three states are possible and
are jointly called triplet state.
• M = 2S + 1 M: multiplicity
• S: total spin
26. Electronic transitions
• Selection rules: allow S→S, and T→T
processes but not S→T and T→S. Ground
states are usually singlets; thus most
excitations are to singlet excited states, like
S0→S1, S0→S2, …
• Triplet states are usually formed by
intersystem crossing from an excited singlet
state, such as S1, rather than by direct
excitation from the S0 ground state.
27. Electronic transitions
• The electronically excited states may decay
unimolecularly back to the ground state by
photophysically emitting energy of fluorescence (from
an excited singlet state) or of phosphorescence (from
an excited triplet state).
• Alternatively, it might decay photochemically to a
different ground state of different structure. One can
thus measure the absorption and emission from
molecules.
• The λmax of an absorption band correspond to the
excitation energy, and εmax to the intensity of transition,
a measure of the probability of promoting an electron,
given the excitation energy.
29. Classification of Electronic
Transitions
• The wavelength of an electronic transition
depends on the energy difference between
the G.S. and the E.S. It is a useful
approximation to consider the λ of to be
determined by the ΔE of MO originally
occupied by the e’s at G.S. and the higher
excited MO in E.S.
• The order: σ ->π ->n->π* ->σ*
31. UV transition type
• 1.σ→σ* transitions: for cpds. with σbond
only, high ΔE, short λ (< 200 nm).
• Appears in satd. hydrocarbons with σ
orbital and transition to antibonding σ* or to
molecular Rydberg orbital (higher valence
shell orbitals, 3s, 3p, 4s, …), and involves
large ΔE, and small λmax that appears in far-
UV region.
• Ex. cyclopropane λmax 190 nm.
• cycloalkane λmax 135 nm. (vacum UV)
32. UV transition type
• 2. n→π* transitions : the excitation of an
electron on an nonbonding orbital, such as
unshared pair e’s on O, N, S,..to an
antibonding π*, usually in an double bond
with hetero atoms, such as C=O, C=S, N=O,
etc. A sym. forbidden and low intensity
transition.
• Ex. satd. aldehydes and ketones : λmax at
185-300 nm.
33. UV transition type
• 3.π→π* transitions : for cpds. containing
double, triple bonds, or aromatic rings; a π
electron is excited to an antibonding π*
orbital. This is usually a sym. allowed and
high intensity transition.
• Ethylene : absorbs at 162 nm (10000), in
vacuum UV. Extended conjugation lowers,
ΔE, and increase in λmax, if extended beyond
5 double bonds then getting into visible
region.
34. UV transition type
• 4. n→σ* transitions: excitation from nonbonding
orbital to an antibonding σ* orbital.
Ex. CH3OH(vap.) 183 nm (ε 150)
NEt3(vap.) 227 nm (900)
MeI(hexane) 258 nm (380)
• 5. Rydberg transition: mainly to higher excited
states. For most organic molecules occurs at λ
below 200 nm. Part of a series of molecular
electronic transitions occurs with narrowing
spacing nearing the ionization potential of organic
molecule.
36. Orbital Spin and E states
• Diagram showing the ground state and excited
state configuration of carbonyl chromophore.
• Singlet state (S) have electron spin paired and
triplet state (T) have two spins parallel.
• n orbital containing two electrons is perpendicular
to πorπ* orbitals.
• Subscript 0 refers to G.S., 1 to 1 st. E.S., 2 to 2 nd.
E.S.
37. Terms describing UV
absorptions
• 1. Chromophores: functional groups that give
electronic transitions.
• 2. Auxochromes: substituents with unshared pair e's
like OH, NH, SH ..., when attached to π chromophore
they generally move the absorption max. to longer λ.
• 3. Bathochromic shift: shift to longer λ, also called red
shift.
• 4. Hysochromic shift: shift to shorter λ, also called blue
shift.
• 5. Hyperchromism: increase in ε of a band.
• 6. Hypochromism: decrease in ε of a band.
38.
39. Orbital Spin States
• Singlet state (S):Most molecules have G.S.
with all electron spin paired and most E.S.
also have electron spin all paired, even
though they may be one electron each lying
in two different orbital. Such states have
zero total spin and spin multiplicities of 1,
are called singlet (S) states.
Total Spin Multiplicities
40. Orbital Spin States
• If an external magnetic field is applied to the
singlet spin system, there is only one zero
angular momentum in the field direction.
• For some of the excited states, there are states
with a pair of electrons having their spins
parallel (in two orbitals), leading to total spin of
1 and multiplicities of 3.
Total spine Multiplicities
41. Orbital Spin States
• For triplet state: Under the influence of
external field, there are three values (i.e. 3
energy states) of +1, 0, -1 times the angular
momentum. Such states are called triplet
states (T).
• According to the selection rule, S→S, T→T,
are allowed transitions, but S→T, T→S, are
forbidden transitions.
42. Selection Rules of electronic
transition
• Electronic transitions may be classed as
intense or weak according to the magnitude
of εmax that corresponds to allowed or
forbidden transition as governed by the
following selection rules of electronic
transition:
• 1. Spin selection rule: there should be no
change in spin orientation or no spin
inversion during these transitions. Thus,
S→S, T→T, are allowed, but S→T, T→S,
are forbidden.
43. Selection Rules of electronic
transition
• 2. Angular momentum rule: the change in
angular momentum should be within one
unit (0 or ±1).
• 3. Symmetry rule: the product of the
electric dipole vector and the group
theoretical representations of the two states
is totally symmetric.
• The spin selection rule simply states that
transitions between states of different
multiplicities are forbidden.
44. Selection Rules of electronic
transition
• The second rule agrees with the fact most states
are within one unit of angular momentum of each
other.
• The symmetry rule indicates that group
representation of initial and final states should be
the same as the representations of axes system
they belong to. If they are different then the
transition moment of that transition is zero and the
transition is thereby forbidden.
• Group representation is the symmetry property of
the orbitals.
45. Allowed and Forbidden
transitions
• Forbidden transition: The n→π* transition of satd.
ketones, where a carbonyl n electron is promoted
to an orthogonal π* orbital (n⊥π*); there is no
orbital overlap for such 90° movement of charge
and the transition moment is zero.
• Allowed transition: For π→π* transition in double
bond, the symmetry of initial and final states are
the same and a large transition moment occurs to
give high intensity of the band.
46. Allowed and Forbidden
transitions
• Forbidden transition: The n→π* transition
of keto group is still observable with low
intensity, this is due to the vibronic states in
the transition. Symmetry of orbital changed
by C=O vibration that allow some overlap
of orbital and the transition to occur.
47. Absorption Intensity
• Shape of electronic absorption band arises
from various vibronic sublevels. The band
intensity is described by εmax in UV. This
quantity can not be calculated theoretically,
but can be calculated by the wave-length
weighted area under the absorption band.
• In UV curve it is called dipole strength D:
in erg cm3, (range 10-34~10-38)
48. Dipole strength
• Dipole strength represents electronic
transition probability of the absorption band.
• As electron is promoted from low to high E.
states, a momentary electric dipole is
generated, called the electric transition
dipole moment μ, which is related to D by:
.
D is a dot product of μ.
49. Dipole strength
• The following relations calculate D in terms
of Δλ (the bandwidth at εmax/2), εmax, and
λmax: