Infrared spectroscopy(IR spectroscopy)
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This presentation by Md. Zahirul Islam provides an overview of infrared (IR) spectroscopy, detailing its principles, types of molecular vibrations, and various applications. It explains the division of the infrared spectrum into near, middle, and far regions, along with characteristic bond vibrations such as stretching and bending. The presentation also highlights the advantages and limitations of IR spectroscopy in identifying substances and analyzing chemical compounds.
Infrared spectroscopy(IR spectroscopy)
- 3. Name: Md. Zahirul Islam Roll:333 Batch:12th Department of pharmacy World University of Bangladesh
- 4. Introduction of Spectroscopy Spectroscopy is the study of the interaction between matter and radiated energy or radiation
- 5. IR spectroscopy Infrared spectroscopy (IR spectroscopy) is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light .
- 6. Principle of IR spectroscopy Molecules are made up of atoms linked by chemical bonds. The movement of atoms and the chemical bonds like spring and balls (vibration) IR radiation does not have enough energy to induce electronic transitions as seen with UV
- 7. Types of IR region They are divided into 3 regions Near IR Region Middle IR Region Far IR Region IR region: 0.8 µm (800nm) to 1000 µm (1mm) Near IR: 0.8-2 µm Middle IR: 2-15 µm Far IR: 15-1000 µm
- 8. Characteristic Vibrational Frequencies of Bonds Bonds are not rigid but behave like a spring with a mass at either end. Obey Hooke’s Law: F = -kx - sign is motion in negative site This gives rise to a characteristic frequency for the vibration: m1 and m2 = Mass of the Atoms in grams in particular bond k = Force constant of the bond. C= velocity of the radiation = 2.998 x cm sec-1 massreduced k _2 1 21 21 _ mm mm massreduced
- 9. Molecular vibrations There are 2 types of vibrations: 1. Stretching vibrations 2. Bending vibrations
- 10. Stretching vibrations Vibration or oscillation along the line of bond Change in bond length Occurs at higher energy: 4000-1250 cm-1 2 types: a) Symmetrical stretching b) Asymmetrical stretching
- 11. Symmetrical stretching: 2 bonds increase or decrease in length simultaneously. H H C
- 12. Asymmetrical stretching in this, one bond length is increased and other is decreased. H H C
- 13. Bending vibrations Vibration or oscillation not along the line of bond These are also called as deformations Occurs at low energy: 1400-666 cm-1 2 types: a) In plane bending: scissoring, rocking b) Out plane bending: wagging, twisting
- 14. Scissoring This is an in plane blending 2 atoms approach each other Bond angles are decrease H H CC
- 15. Rocking Movement of atoms take place in the same direction. H H CC
- 16. Wagging 2 atoms move to one side of the plane. They move up and down the plane. H H CC
- 17. Twisting One atom moves above the plane and another atom moves below the plane. H H CC
- 18. Application of IR spectroscopy 1. Identification of Substances 2. The “Fingerprint” Region (1200 to 700 cm-1) : 3. Computer Search Systems: 4. . Determination of Molecular Structure 5. Studying Progress of Reactions 6. Detection of Impurities 7. Isomerism in Organic Chemistry 8. Presence of Water in Sample 9. Measurement of Paints & Varnishes
- 19. Advantage of IR spectroscopy 1. Detection (health condition) 2. Prevention (early diagnosis) 3. Monitoring 4. Diagnosis (under investigation) 5. Application of IR spectroscopy as a analytical tool varies widely from one laboratory to other. 6. Quantitative IR analysis is based on Beer’s law.
- 20. Limitation of IR spectroscopy 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.
- 21. Thanks To all