Infrared spectroscopy(IR spectroscopy)

Introduction of Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy or radiation.
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.
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

Types of IR region
 Infrared region
 LIMIT OF RED LIGHT: 800 nm, 0.8 m, 12500 cm-1
 NEAR INFRARED: 0.8 -2.5 m, 12500 - 4000 cm-1
 MID INFRARED: 2.5 - 25 m, 4000 - 400 cm-1
 FAR INFRARED: 25 - 1000 m, 400 - 10 cm-1
Molecular vibrations
There are 2 types of vibrations:
1. Stretching vibrations
2. Bending vibrations
 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

Symmetrical stretching: 2 bonds increase or decrease in length simultaneously
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

1. Presentation of IR Spectroscopy

2. Welcome To My Presentation

3. Name: Md. Zahirul Islam Roll:333 Batch:12 th 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 a s seen with UV

7. Types of IR region They are divided into 3 regions Near IR Region Middle IR Region Far IR Region

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: m 1 and m 2 = 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

9. Molecular vibrations There are 2 types of vibrations: Stretching vibrations 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: Symmetrical stretching 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: In plane bending : scissoring, rocking Out plane bending : wagging, twisting

14. Scissoring This is an in plane blending 2 atoms approach each other Bond angles are decrease H H C C

15. Rocking Movement of atoms take place in the same direction. H H C C

16. Wagging 2 atoms move to one side of the plane. They move up and down the plane. H H C C

17. Twisting One atom moves above the plane and another atom moves below the plane. H H C C

18. Application of IR spectroscopy Identification of Substances The “Fingerprint” Region (1200 to 700 cm -1 ) : Computer Search Systems: . Determination of Molecular Structure Studying Progress of Reactions Detection of Impurities Isomerism in Organic Chemistry Presence of Water in Sample Measurement of Paints & Varnishes

19. Advantage of IR spectroscopy Detection (health condition) Prevention (early diagnosis) Monitoring Diagnosi s (under investigation) Application of IR spectroscopy as a analytical tool varies widely from one laboratory to other. 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