Infra red spectroscopy.
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Infrared spectroscopy involves the interaction of infrared radiation with matter. It is based on absorption spectroscopy and deals with the absorption of infrared radiation which causes vibrational transitions in molecules. There are two main types of molecular vibrations observed in infrared spectroscopy - stretching vibrations which involve changes in bond lengths, and bending vibrations which involve changes in bond angles. Infrared spectroscopy can be used to determine the structure of organic compounds and identify functional groups and impurities in pharmaceutical applications.
Infra red spectroscopy.
- 2. 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 3
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- 5. Molecular Vibration (The dipole moment of the molecule must change as a result of a molecular vibration.) MOLECULAR VIBRATIONS Fundamental Vibrations Stretching Vibration Symmetri c Asymmetri c Bending Vibration In-plane Bending Scissoring Rocking Out Of Plane Bending Waggin g Twistin g Non-fundamental Vibrations Over Tones, Combination Tones, Fermi Resonance 5
- 6. 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 stretching 2. Asymmetrical stretching STRETCHIN G 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 bending 2. Out plane bending BENDING VIB. 6 Stretching Mode
- 7. 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. 7
- 8. 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 bending i. 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 bending i. Scissoring: • Bond angles are decrease. ii. Rocking: • Movement of atoms is same direction. 8
- 9. 9 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). 10
- 11. 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. 11
- 13. 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 13
- 14. SOURCE 14 1. 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)
- 15. 3. Tungsten Filament Lamp 4. Hg & Xe Arc Lamp 15
- 16. MONOCHROMATORS Monochromators Composed Types 1. 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 16
- 18. 18 1. Thermocouple detector 2. Bolometer - Wheatstone bridge
- 19. Dispersive IR o Double-beam instruments are mostly used than Single beam instrument. o In dispersive IR sequential scanning of wave numbers of light takes place. • In double beam spectrometer, beam separates into two and passes to sample & reference. • Prismatic monochromators have been replaced with Grating monochromator. 19
- 20. 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 20
- 21. Interferometer He-Ne gas laser Fixed mirror Movable mirror Sample chamber Light source Detector Beam splitter FTIR Instrumentation 21
- 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. 22
- 23. 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 23
- 24. 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 24
- 26. TYPES OF VIBRATIONS Stretching Mode In plane bending vibrations Scissoring Rocking Out plane bending vibrations Wagging Twisting Symmetric Asymmetric 26