Infra red spectroscopy.
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Transcript of Infra red spectroscopy.
INFRA-RED SPECTROSCOPY
Siddharth Kumar SahuM.Pharmacy
IR spectroscopy is deals with the interaction of infrared region of the electromagnetic spectrum with the matter.
It concerned with the study of absorption of infrared radiation, which causes vibrational transition in the molecule.
It is based on absorption spectroscopy.
IR-radiation
vibration changes
in electrons
IR spectrum
Introduction
3
Middle IR:2.5-25 mm
IR region:0.8-1000 mm
(800nm-1mm)
Far IR:25-1000
mm
Near IR:0.8-2.5 mm
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5
Molecular Vibration(The dipole moment of the molecule must change as a result
of a molecular vibration.)MOLECULA
R VIBRATION
S
Fundamental Vibrations
Stretching
Vibration
Symmetric
Asymmetric
Bendin
g Vibratio
nIn-planeBending
Scissoring
Rocking
Out Of Plane
Bending
Wagging
Twisting
Non-fundamental Vibrations
Over Tones,
Combination
Tones,Fermi
Resonance
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Types of Fundamental Vibration
1. Change in the bond length b/w 2 atoms.
2. It requires more energy so appear at shorter wavelength.
Types:-1. Symmetrical stretching2. Asymmetrical stretching
STRETCHING VIB.
1. Change in the bond angle b/w two bonds.
2. It requires less energy so appear at longer wavelength.
Types:-1. In plane bending2. Out plane bending
BENDING VIB.
Stretching Mode
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Stretching Vibration • B.) Asymmetrical
stretching:
• in this, one bond length is increased and other is decreased.
• A.) Symmetrical stretching:
• 2 bonds increase or decrease in length simultaneously.
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Bending Vibration a) In plane bending- all the atom are same plane.b) Out plane bending- 2 atom, 1 same plane & 1 atom is on opposite plane.
b.) Out plane bendingi. Wagging:• 2 atoms move to one
side(up & down) of the plane.
ii. Twisting:• 2 atom where 1moves
above & 1 moves below the plane.
a.) In plane bendingi. Scissoring:• Bond angles are
decrease.
ii. Rocking:• Movement of atoms is
same direction.
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NON-FUNDAMENTAL
OVER TONES:These are
observed at twice the
frequency of strong band.Ex: carbonyl
group.
COMBINATION TONES:
Weak bands that appear
occasionally at frequencies that
are sum/difference
of 2 or more fundamental
bands.
FERMI RESONANCE:
Interaction b/w fundamental vibration & overtones or combination
tones.Ex: CO2
NON-FUNDAMENTAL VIBRATIONS
10
Structure Determination of Organic Compounds through Infrared
Spectroscopy• Parameters• The spectrophotometer give the spectra of certain
wave by indicating the quality of wave and the quantity of wave that how much wave is absorbed by the molecule (Transmittance).
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The IR Spectrum• There are two type of IR Spectra from which we can
obtained the information about the quality of molecule . • The Functional Group region: Identifies the functional group
with the consequence of changing stretching vibrations. Ranges from 4000 to 1600 cm-1.
• The Fingerprint region: Identifies the exact molecule with the consequence of changing bending vibrations. Ranges from 1600 to 625cm-1.
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Instrumentation
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TYPES OF IR INSTRUMENTS
• Filters used for wavelength selection & having sample specific Detector
1. Non- Dispersive
• Sequential scanning of each wave number takes place 2.Dispersive
• Widely applied and quite popular in the far-IR and mid-IR spectrometry.
3. FTIR systems
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SOURCE1. Nernst glower Heated rare earth
oxide rod (zirconium, yttria, thoria) (temp. 1500*C)
7100 cm-1 rad. (mid to far IR)
2. Globar Heated silicon carbide rod (1500*C)
5200 cm-1rad. (mid to far IR)
3. W filament lamp 1100*C (near IR )
4. Hg arc lamp Hg plasma (far IR)
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3. Tungsten Filament Lamp
4. Hg & Xe Arc Lamp
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MONOCHROMATORSMonochromators Composed Types1. Prismatic glass/quartz &
coated by alkyl halide ( NaCl )
I. Mono pass P.M.II. Double pas
P.M.
2. Grating Grooves or lines made up of Al.
I. Reflection Grating II. Transmittance
Gratings
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DetectorsName Composed Advantage S.N
1.
2.
3.
4.
5.
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1. Thermocouple detector
2. Bolometer - Wheatstone bridge
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Dispersive IRo Double-beam instruments are mostly used than Single beam
instrument.o In dispersive IR sequential scanning of wave numbers of light
takes place.Instrumentation• In double beam spectrometer, beam separates into two and
passes to sample & reference. • Prismatic monochromators have been replaced with Grating
monochromator.
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Fourier Transform IR Instrument
o FTIR collects all wavelengths simultaneously and scans at once.
o FTIR works based on Michelson Interferometer which having
• Beam splitter• Fixed mirror• Movable mirror
21Interferometer
He-Ne gas laser
Fixed mirror
Movable mirror
Sample chamber
Light source
Detector
Beam splitter
FTIR Instrumentation
22
General Purpose Of IR Radiation
Infrared light is used in industrial, scientific, and medical applications.
• In Telescopes to detect planets• Finding heat leaks from houses• Infrared thermal-imaging cameras are used to detect heat loss
in insulated systems,• to observe changing blood flow in the skin,• to detect overheating of electrical apparatus.• Night-vision devices• Remote temperature sensing, short-ranged
wireless communication, spectroscopy, and weather forecasting.
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Pharmaceutical Applications
Qualitative determination of substances
Structural elucidation by determining the functional groups.
Detection of impurities
Identification of geometrical isomers for both organic & inorganic samples
Detection of presence of water in sample
Quantitative determination of sample by using Beer’s-Lamberts law
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REFERENCE• Chatwal G.R. . A textbook of ‘Instrumental Method
Of Chemical Analysis’. • www.Slideshare.com • instrupres-140329002030-phpapp01• uttam-ir-140929003810-phpapp02• irspectroscopy-140210002609-phpapp01
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TYPES OF VIBRATIONS
Stretching Mode
In plane bending vibrations
Scissoring
Rocking
Out plane bending vibrations
Wagging
Twisting
Symmetric
Asymmetric