U G and PG students

1. IR
By
Mr. G. P. Sadawarte
Asst. Professor, Dept. of Chemistry
B. P. Arts, S.M.A. Sci. and K.K.C. Comm. College
chalisgaon
B.P. Arts, S.M.A. Science And K.K.C.
Commerce College, Chalisgaon,

2. Introduction

5. Division Of IR
Near IR : 0.8 to 2.5 (12500- 4000 per cm)
IR : 2.5 to 15 (4000 to 667 per cm)
Far IR : 15 to 200 (667 to 50 per cm)
IR
Functional Group : 2.5 to 7.7 (4000 – 1300)
Finger Print :7.7 to 11 (1300 - 909)
Aromatic : 11 to 15 (909 - 667)

6. Fundamental Modes of Vibration
1) Stretching Vibration
2) Bending Vibration
1) Stretching Vibration- Change in inter nuclear
Distance
a) Symmetric Stretching
a) Asymmetric Stretching

8. Bending Vibration- Change in angle between two
axis
• Bending in plane
scissoring Rocking
• Bending in out of plane
Wagging Twisting

10. Functional Group Region

11. Alkane
• 2850 to 2950 /cm C-H Streching
• 800 – 1200 /cm bending vibration frequency
not useful for identification
Alkene
• C=C 1620 – 1680 / cm
• Mono substituted 1640/ cm

13. Alkene
•Tetra substituted
• 1670/cm
Tri substituted
•1670 /cm
Disubstuted
•Cis 1650 /cm
•Trans 1670 /cm

14. Alkyne
• C = C Stretching Frequency 2200 /cm
• C = N Stretching Frequency 2200 - 2250 /cm
• C = C- H Stretching Frequency 3300 /cm
• C = C- H bending vibration 610- 700 /cm

17. Aromatic C=C
•C=C stretching frequency range 1500 – 1600 / cm
•C=C-H stretching frequency 3000 – 3100 / cm
•C=C-H Bending frequency 675 – 710 / cm
H
H
H
H
H
H

18. Alcohol and Phenol
•Alcoholic and Phenolic OH group shows strong, broad
absorption band in range 3200- 3600 /cm
•Another strong band due to O — C in range 1000 – 1200
per cm
•C-O stretching frequency
•Primary alcohol :1050 per cm
•Secondary alcohol :1100 per cm
•Tertiary alcohol :1150 per cm
•Phenol :1230 per cm
R OH
OH

20. Ether
R– O – R
Ether C– O – C shows stretching range between
1000- 1300 per cm
R
O
R
C
O
C

22. Alkyl Halide
R X
C – X : 1150 to 1300 /cm

23. Carbonyl (1730-1715)
Aldehyde
• C=O :1720-1725 /cm
• C– H 2720-2830 /cm
(2750)
Ketone
• C=O 1715 /cm

25. Carboxylic Acid
• C= O : 1730 /cm
• OH gives broad band : 2700 – 3300 /
cm

27. Ester
•C= O : 1735- 1750/cm
•C– O gives band : 1180 – 1200 / cm

29. Amide
•C= O : 1600/cm
•N– H gives band : 3300/ cm

31. Amine
• Primary amine give two band :
• 3350- 3500 /cm
• 3250- 3450 /cm
• Bending vibration :1510-1650
Secondary amine gives only one band
3200- 3600 /cm

34. Application of IR
• Structure Determination
• Study the chemical reaction
• Determination of Hydrogen bonding
• Determination of Ring Size
• Detection of purity

35. Problems
OH O
CrO3
NO2
NH2
HNO3
H2 SO4
H2
Pd/C
How will you follow the follwing reaction path by IR

36. Problems
1. An organic compound having Mol. F. C4 H6 shows IR
Band at 2100 And 3300 /cm find out structural
formula of compound
2. An organic compound having Mol. F. C6 H10 O shows IR
Band at 1690/cm and UV shows absorption at 240nm,
find out structural formula of compound
3. An organic compound having Mol. F. C3 H6 O shows IR
Band at 1720 And 2720 /cm find out structural
formula of compound

37. References
• Introduction to Spectroscopy, Donald L. Pavia Gary
M. Lampman George S. Kriz James R. Vyvyan,
• Spectroscopy by Y.R. Sharma S. Chand Publication
• Spectrometric Identification of Organic Compounds,
R. M. Silverstein and F. X. Webster , John Wiley and
Sons

38. Problems
How will you distinguish the following pair by IR
• Benzoic acid and m hydroxy Benzaldehyde
• Phenol and Cyclohexanol
• M-Cresol and anisol
• Acetone acetic and acetic acid
• Nitrobenzene and aniline

39. Functional Group and IR

40. Functional Group and IR

41. Any ?