Fluorimetry, principle, Concept of singlet,doublet,and triplet electronic sta...Vandana Devesh Sharma
Content-Principle
concept of singlet, doublet and triplet electronic stages,
Internal and external conversions,
Factors affecting fluorescence,
quenching,
Instrumentation and
applications
Types of luminescence including
bioluminescence,
chemiluminescence,
Fluorescence, and
phosphorescence
These various forms of luminescence differ in their method of emitting light.
Bioluminescence
Chemiluminescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds)
Fluorescence starts immediately after the absorption of light and stops as soon as the incident light is cut off
Eg -The fluorescent clothes, shoes
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds)
Fluorescence starts immediately after the absorption of light and stops as soon as the incident light is cut off
Eg -The fluorescent clothes, shoes
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds)
Fluorescence starts immediately after the absorption of light and stops as soon as the incident light is cut off
Eg -The fluorescent clothes, shoes
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds)
Fluorescence starts immediately after the absorption of light and stops as soon as the incident light is cut off
Eg -The fluorescent clothes, shoes
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds) Fluorimetry
An analytical technique for identifying and characterizing minute amounts of substance by excitation of the substance with a beam of ultraviolet/Visible light and detection and measurement of the characteristic wavelength of fluorescent light emitted.Excited – State Processes in molecules
Fluorimetry, principle, Concept of singlet,doublet,and triplet electronic sta...Vandana Devesh Sharma
Content-Principle
concept of singlet, doublet and triplet electronic stages,
Internal and external conversions,
Factors affecting fluorescence,
quenching,
Instrumentation and
applications
Types of luminescence including
bioluminescence,
chemiluminescence,
Fluorescence, and
phosphorescence
These various forms of luminescence differ in their method of emitting light.
Bioluminescence
Chemiluminescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds)
Fluorescence starts immediately after the absorption of light and stops as soon as the incident light is cut off
Eg -The fluorescent clothes, shoes
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds)
Fluorescence starts immediately after the absorption of light and stops as soon as the incident light is cut off
Eg -The fluorescent clothes, shoes
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds)
Fluorescence starts immediately after the absorption of light and stops as soon as the incident light is cut off
Eg -The fluorescent clothes, shoes
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds)
Fluorescence starts immediately after the absorption of light and stops as soon as the incident light is cut off
Eg -The fluorescent clothes, shoes
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation
In fluorescence, absorption and emission light takes place in very short time (10-12 or 10-9 seconds) Fluorimetry
An analytical technique for identifying and characterizing minute amounts of substance by excitation of the substance with a beam of ultraviolet/Visible light and detection and measurement of the characteristic wavelength of fluorescent light emitted.Excited – State Processes in molecules
Various factor affecting vibrational frequency in IR spectroscopy.vishvajitsinh Bhati
various factor affecting vibrational frequency in IR,
• Coupled vibrations
• Fermi resonance
• Electronic effects
• Hydrogen bonding
and their examples
a substance can absorb any visible light or external radiation and then again emit it. this called fluorescence and the process of reduction in fluorescence intensity is called quenching. this presentation is all about quenching of fluorescence.
Approaches Of Gastro-Retentive Drug Delivery System or GRDDSAkshayPatane
Approaches Of Gastro-Retentive Drug Delivery System
Includes:
Floating and Non-Floating drug delivery system with their subtypes
Like Non-effervescent system, Effervescent system, Raft forming system,
High Density system, Expandable system, Muco-adhesive system,
Super porous hydrogel system and Magnetic Systems, etc.
The device which is used in the intrauterine drug delivery system is known as an Intrauterine device (IUD) (2). IUDs or intrauterine devices are small artificial objects or devices inserted into the uterus to prevent the occurrence of pregnancy by disrupting the fertilization process as a result of sexual intercourse. They have gained popularity in recent times and are one of the most effective methods of birth control in terms of long-term contraception. It can be easily installed and is flexible. These devices are usually small in size and inserted through the cervix. IUDs reduce the need for abortion with unwanted pregnancies by preventing the effective movement of eggs and sperm. However, it cannot confirm the spread of STIs or STDs such as HIV, gonorrhoea, etc
Topics covered
Introduction
Advantages
Disadvantages
Development of intra uterine devices (IUDs)
Applications
References
Gastro retentive drug delivery system (GRDDS)Shweta Nehate
Oral route is the most acceptable route for drug administration. Apart from conventional dosage forms several other forms were developed in order to enhance the drug delivery for prolonged time period and for delivering drug to a particular target site. Gastro-retentive drug delivery system (GRDDS) has gainned immense popularity in the field of oral drug delivery recently. it is a widely employed approach to retain the dosage form in the stomach for an extended period of time and release the drug slowly that can address many challenges associated with conventional oral delivery, including poor bioavailability. different innovative approaches are being applied to fabricate GRDDS. Gastroretentive drug delivery is an approach to prolong gastric residence time, there by targeting site-specific drugs release in the upper gastrointestinal tract (GIT) for local or systemic effects. It is obtained by retaining dosage form into stomach and by releasing the in controlled manner.
Various factor affecting vibrational frequency in IR spectroscopy.vishvajitsinh Bhati
various factor affecting vibrational frequency in IR,
• Coupled vibrations
• Fermi resonance
• Electronic effects
• Hydrogen bonding
and their examples
a substance can absorb any visible light or external radiation and then again emit it. this called fluorescence and the process of reduction in fluorescence intensity is called quenching. this presentation is all about quenching of fluorescence.
Approaches Of Gastro-Retentive Drug Delivery System or GRDDSAkshayPatane
Approaches Of Gastro-Retentive Drug Delivery System
Includes:
Floating and Non-Floating drug delivery system with their subtypes
Like Non-effervescent system, Effervescent system, Raft forming system,
High Density system, Expandable system, Muco-adhesive system,
Super porous hydrogel system and Magnetic Systems, etc.
The device which is used in the intrauterine drug delivery system is known as an Intrauterine device (IUD) (2). IUDs or intrauterine devices are small artificial objects or devices inserted into the uterus to prevent the occurrence of pregnancy by disrupting the fertilization process as a result of sexual intercourse. They have gained popularity in recent times and are one of the most effective methods of birth control in terms of long-term contraception. It can be easily installed and is flexible. These devices are usually small in size and inserted through the cervix. IUDs reduce the need for abortion with unwanted pregnancies by preventing the effective movement of eggs and sperm. However, it cannot confirm the spread of STIs or STDs such as HIV, gonorrhoea, etc
Topics covered
Introduction
Advantages
Disadvantages
Development of intra uterine devices (IUDs)
Applications
References
Gastro retentive drug delivery system (GRDDS)Shweta Nehate
Oral route is the most acceptable route for drug administration. Apart from conventional dosage forms several other forms were developed in order to enhance the drug delivery for prolonged time period and for delivering drug to a particular target site. Gastro-retentive drug delivery system (GRDDS) has gainned immense popularity in the field of oral drug delivery recently. it is a widely employed approach to retain the dosage form in the stomach for an extended period of time and release the drug slowly that can address many challenges associated with conventional oral delivery, including poor bioavailability. different innovative approaches are being applied to fabricate GRDDS. Gastroretentive drug delivery is an approach to prolong gastric residence time, there by targeting site-specific drugs release in the upper gastrointestinal tract (GIT) for local or systemic effects. It is obtained by retaining dosage form into stomach and by releasing the in controlled manner.
Introduction
Instrumentation
Sampling techniques
Group frequencies
Factors affecting group frequencies
Complementarity of IR and Raman spectroscopy
Applications of Infrared spectroscopy
This PPT gives viewers a complete guidance and understanding of various topics of IR spectroscopy. Highly useful to the students of Chemistry,Physics,Lifescienes and Pharmacy.
Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with the matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
How to Split Bills in the Odoo 17 POS ModuleCeline George
Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
4. Spectroscopy
“seeing the un seeable”
Using electromagnetic radiation as a probe to
obtain information about atoms and molecules
that are too small to see.
Electromagnetic radiation is propagated at the
speed of light through a vacuum as an
oscillating wave.
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7. λ = wave length
υ = frequency
c = speed of light
E = kinetic energy
h = Planck’s constant
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8. The electromagnetic spectrum contains many types of waves, one of which
is infrared waves. Other electromagnetic waves include gamma rays, x-
rays, ultraviolet, visible light, microwaves, and radio.
Infrared Spectroscopy includes radiation with wavelengths between 2.5 µm
– 25 µm.
Technically correct Unit is µm( micrometer) but often used unit is µ
(micron).
But mostly referred unit is wave number( Reciprocal centimeter (cm )
Infrared Spectroscopy generally refers to the analysis of the interaction of a
molecule with infrared light.
An IR spectrum is essentially a graph plotted with the infrared light
absorbed on the Y-axis against. frequency or wavelength on the X-axis.
The major use of infrared spectroscopy is to determine the functional
groups of molecules, relevant to both organic and inorganic chemistry.
IR Spectroscopy detects frequencies of infrared light that are absorbed by a
molecule. Molecules tend to absorb these specific frequencies of light since
they correspond to the frequency of the vibration of bonds in the molecule.
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-1
9. The energy required to excite the bonds belonging to a
molecule, and to make them vibrate with more amplitude,
occurs in the Infrared region. A bond will only interact with
the electromagnetic infrared radiation, however, if it is polar.
Regions of IR
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10. In other words, IR spectra is nothing but a finger print region of a
molecule.
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11. Dipole Moment:
The bonds in a molecule can absorb IR radiation
only when there is a change in dipole moment due
to electric field of IR radiation.
Applied IR frequency should be equal to the natural
frequency of radiation, otherwise compounds do
not give IR peaks
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14. Vibration along the line of bond.
Change in bond length.
2 types:
a) Symmetrical stretching
b) Asymmetrical stretching
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15. a) Symmetrical stretching
Both bonds increase or decrease in length
simultaneously.
b) Asymmetrical stretching
In this, one bond length is increased and
other is decreased.
Asymmetrical stretching
vibrations occur at higher
frequency than Symmetrical stretching
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17. Vibration not along the line of bond.
In this, bond angle is altered.
Occurs at lower frequencies than stretching vibrations.
2 types:
a)In plane bending:
i. Scissoring
ii. Rocking
b)Out plane bending:
i. Wagging
ii. Twisting
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18. a)In plane bending:
i. scissoring :
This is an in plane bending
Bond angles are decrease
ii. Rocking :
Bond angle is maintained.
Movement of atoms take place in the same
direction.
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19. b) OUT PLANE BENDING
vibrations takes place outside the plane of molecule.
i. Wagging:
both atoms move to one side of the plane.
ii. Twisting:
One atom moves above the plane and another atom
moves below the plane
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23. NIP, Pune. 23
➢Sample handling is considered as an important technique in the infrared
spectroscopy.
➢The samples used in IR spectroscopy can be either in the solid, liquid, or
gaseous state.
➢ Samples of different phases have to be handled differently.
➢Common point is that the material containing the sample must be
transparent to IR radiations.
a) Sampling of solids:
• Solid runs in solution- solid dissolved in non-aq. ---drop of solution is
placed on an alkali metal disk ---solvent allow to evaporate---thin film of
solute is formed(some time entire solution is placed in a liquid sample cell)
• Solid films- if solid is amorphous in nature—the sample is deposited on
the surface of KBr or NaCl by evaporation of solution of solid.
24. • Mull technique-nujol mull( mineral oil)
• Pressed pellet technique-
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Sample+ nujol Nujol
mull(thick paste) spread
between IR transmitting
window & the mounted in
path of infrared beam,
spectrum is run.
• Nujol mull is transparent
through IR region but shows
absorption maximas at
2915,1462,1376,719 cm-1
Sample + KBr mixture is passed
under very high pressure in
press(2500 Psi). Formed pellet is
transperant to IR radiations & is run
as such.
( blank KBr pellet-reference beam)
•Resolution of spectrum is superior.
•Stored for long time.
25. b) Sampling of liquids:
Liquid samples are generally kept between two salt
plates of salts and measured since the plates are
transparent to IR light. Salt plates can be made up
of sodium chloride, calcium fluoride, or even
potassium bromide.
c) Sampling of Gases:
Since the concentration can be in parts per million,
the sample cell must have a relatively long
pathlength, i.e. light must travel for a relatively long
distance in the sample cell.
samples of multiple physical states can be used in
Infrared Spectroscopy.
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28. Fundamental Vibrations- Fundamental vibrational frequencies of a molecule
corresponds to transition from v=0 to v=1.
For a non-linear molecule there will by 3N-6 (where N is the number of atoms)
number vibrations. The same holds true for linear molecules, however the
equations 3N-5 is used, because a linear molecule has one less rotational degrees
of freedom.
Overtone- Overtones occur when a vibrational mode is excited from v=0 to v=2,
which is called the first overtone, or v=0 to v=3, the second overtone.
Combination band- combination bands are observed when more than two or more
fundamental vibrations are excited simultaneously. One reason a combination
band might occur is if a fundamental vibration does not occur because of
symmetry.
Difference band-Difference bands are similar to combination bands. The observed
frequency in this case results from the difference between the two interacting
bands.
Usually spectrum is complicated because of presence of weak overtone,
Combination band and Difference band.
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29. The value of stretching vibrational frequency of a bond
can be calculated by using HOOKE’S LAW.
Value of vibrational frequency or wave number
depends upon:
Bond strength
Reduced mass
Ex: C=C has higher vibrational frequency than C-C
stretching.
O-H has higher vibrational frequency than C-C
bonding.
F-H has higher vibrational frequency than O-H
stretching.
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33. Vibrations which occurs at different frequencies than that
required for an isolated vibrations (stretching) are called
coupled vibrations.
Eg. Consider methylene group(-CH2-) two absorptions occurs
which corresponds to symmetric and asymmetric stretching
vibrations.
Eg. Consider methyl group(-CH3-) two absorptions occurs
which corresponds to symmetric and asymmetric stretching
vibrations.
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34. A Fermi resonance is the shifting of the energies and
intensities of absorption bands in an infrared or Raman
spectrum.
In IR spectrum, absorption bands are spread over a wide
range of frequencies. Then the energy of a overtone level
chances to coincide with the fundamental mode of different
vibrations. This type of resonance is called Fermi Resonance.
This phenomenon was first observed by Enrico Fermi in case
of carbon dioxide.
Ex: Carbon dioxide (triatomic) linear and four fundamental
vibrations are expected. In this two symmetric stretching
vibration is IR inactive(no change in dipole moment).
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37. The frequency shifts from the normal position of
absorption because of electronic effects.
The force constant or the bond strength
changes and it’s absorption frequency shifts
from normal value.
The frequency shifts includes:
Inductive Effect
Mesomeric Effect
Field Effect
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38. It is the electronic effect occurs due to polarization
of sigma bonds within the molecules or ion.
Introduction of alkyl groups causes + I effect.
It results in lengthening or weakening of the bond
and hence the force constant is lowered and wave
number of absorption decreases.
Eg. wave number for c=o for following compounds
Formaldehyde 1750 cm-1
Acetaldehyde 1745 cm-1
Acetone 1715 cm-1
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39. The introduction of electronegative atom
causes – ve I effect.
It results in the increase of bond order.
Thus the force constant increases and hence
the wave number of the bonds also increases.
Eg.
Acetone 1715 cm-1
Chloroacetone 1725 cm-1
Dichloroacetone 1740 cm-1
Tetachloroacetone 1750 cm-1
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40. Conjugation occurs between two pi bonds or
a pi bond and lone pair of electrons present
on an adjacent atom.(polarity is produced)
In some cases –I effect is dominated by
mesomeric effect and the absorption
frequency falls.
Ex: Absorption frequency of amides and
esters
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41. Lone pair of electrons present on the atoms
influence each other through space
interactions and changes the vibrational
frequencies of both the groups.
This effect is called as Field effect.
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Ortho halo acetophenon
42. Hydrogen bonding gives rise to downward
frequency shifts.
Stronger is the hydrogen bonding, greater is
the absorption shift towards lower wave
numbers.
Hydrogen bonding is of two types
Intermolecular hydrogen bonding
Intramolecular hydrogen bonding
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43. INTERMOLECULAR HYDROGEN BONDING
Gives rise to broad bands
These are concentration dependent.
INTRAMOLECULAR HYDROGEN BONDING
Gives rise to sharp and well defined bands.
These are concentration independent.
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44. The main parts of IR spectrometer are as follows
1. IR radiation sources
2. Monochromators
3. Sample cells and sampling of substances
4. Detectors
5. recorders
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50. In far IR region (<200cm-1) the described
sources lose their effectiveness at that time
mercury arc lamps are used.
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51. A. Prism:-
Used as dispersive element.
Constructed of various metal halide salts.
Sodium chloride is most commonly prism salt
used.
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53. Grating are nothing but rulings made on some
materials like glass, quartz or alkylhalides
depending upon the instrument.
The mechanism is that diffraction produces
reinforcement.
The rays which are incident upon the gratings
gets reinforced with the reflected rays.
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55. Made up of alkali halides like NaCl or KBr .
Aqueous solvents cannot be used – they dissolve
alkali halides.
Only organic solvents like chloroform is used.
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56. a) Sampling of solids
Solids run in solution
Mull technique
Pressed pellet technique
Solids films
b) Sampling of liquids
c) Sampling of gases
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57. Detectors are used to measure the intensity of
unabsorbed infrared radiation.
The detectors can be classified into three categories:
Thermal detectors
Pyroelectric detectors
Photoconducting detectors
DETECTORs:
Bolometers detector
Thermocouple
Thermistors
Golay cell
Pyro electric detector
Photocoductivity detector
Semiconductor detectors
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58. Thermal detectors can be used over a wide range of
wavelengths and they operate at room temperature.
Their main disadvantages are slow response time and
lower sensivity relative to other types of detectors.
Bolometers detector
Thermocouple
Thermistors
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64. Made up of fused mixture of metal oxides
As the temperature of mixture increases
It’s electrical resistance decreases
(opposite to bolometer)
Response time is slow
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65. Golay cell consists of a small metal cylinder
closed by a rigid blackened metal plate at one
side and by a flexible metal diaphragm at other
end.
Pneumatic chamber is filled with xenon gas and
sealed.
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66. When infra red radiation is passed through infrared
transmitting window the blackened plate absorbs the
heat.
By this heat the xenon gas expands, The resulting
pressure of gas will cause deformation of diaphragm.
This motion of the diaphragm detects how much IR
radiation falls on metal plate.
Light is made to fall on diaphragm which reflects light
on photocell
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67. Pyroelectric detector contain certain crystal Such
as lithium tantalate, barium titanate and
triglycine sulfate
They produce temperature sensitive dipole
moments.
To construct a pyroelectric detector, pyroelectric
substance is placed between two electrodes .
Two electrodes are connected to each other via a
voltmeter.
one of which has IR transparent window.
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68. When the IR radiation falls upon a pyroelectric
substance, it absorbs energy from the
radiation.
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69. This is non-thermal detector of great
sensitivity.
Consists of thin layer of lead sulphide or lead
telluride supported on glass and enclosed into
an evacuated glass envelope.
When IR radiation is focused on lead sulphide
or lead telluride, its conductance increases and
causes more current to flow.
Response time is 0.5msec.
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70. Exposure to radiation causes very rapid
change in their electrical resistance and
therefore very rapid response to IR signal.
The basic concept behind this system is that
IR photon displaces an electron in the
detector, changing it’s conductivity.
The response time for this detector is the
time required to change the semiconductor
from insulator to conductor.
It is very short -1 nsec.
Eg. Lead sulphide detector
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71. Recorders are used to record the IR spectrum
The radiant energy received by detector is
converted into measurable electrical signal
and is amplified by amplifier.
The amplified signals are recorded and
plotted.
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72. There are 2 types of infrared spectrophotometer
characterized by the manner in which the IR
frequencies are handled.
1) dispersive type (IR)
2) Interferometric type(FTIR)
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73. In dispersive type the infrared light is separated
into individual frequencies by dispersion, using a
grating monochromator.
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77. In interferometric type the IR frequencies are
allowed to interact to produce an interference
pattern and this pattern is then analyzed, to
determine individual frequencies and their
intensities.
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79. Identification of functional group and structural
elucidation.
Identification of drug substances.
Identifying impurities in drug sample.
Study of hydrogen bonding.
Study of polymers.
Identify ratio of cis-trans isomers in a mixture of
compounds.
Quantitative analysis.
To find out difference between hydrogen bonding.
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80. With IR spectroscopy it is not possible to
know molecular weight of substance.
It is frequently non-adherence to Beer’s law
of complexity spectra.
The narrowness of spectra and effect of stray
radiations make the measurements of
absorbance upon slit width and wavelength
setting.
Generally, IR spectroscopy does not provide
information of the relative positions of
different functional groups on a molecule.
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85. Elementary organic spectroscopy, principles
andchemical applications, Y. R. Sharma.
Instrumental methods of pharmaceutical
analysis, Dr. Gurdeep Chatwal, Dr. Anand.
Introduction to Spectroscopy by Pavia,
Lampman & Kriz.
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