1. Aromatics Prominent (strong) features: C-H stretch 3100-3000
in-plane C-H bend
out of plane C-H bend
C=C ring stretches and
out of plane C=C bend

2. combination bands

3. IR of Alcohols O-H bend overlaps C-H bend 1209 C-O stretch 1023
O-H H-bonded
3331

4. IR of Alcohols cyclohexylcarbinol O-H non-hydrogen bonded
or free OH
(sharp bands in gas phase)
Intermolecular H-Bonding
in solution increase with
concentration gives bands
at (broader)

5. Ethers and Epoxides
Ethers: C-O-C asymmetric stretch (strong)
C-O-C symmetric stretch is usually weak at
Epoxides: ring stretch near 1250 and

6. Carbonyl Groups
Ketones, aldehydes, carboxylic acids, carboxylic esters,
lactones, acid halides, anhydrides, amides, lactams
all show C=O stretch

7. IR of 2-Pentanone
C-CO-C stretch 1171
C=O stretch 1717

8. Carbonyl Groups normal aliphatic ketones (acetone, cyclohexanone) 1715
replacement of alkyl group by heteroatom (G) shifts
C=O stretch
direction depends on inductive
or resonance effect
inductive: increases C=O freq.
resonance: decreases

9. Effect of G G C=O Inductive Cl 1815-1785 F 1869 Br 1812
OH (monomer) 1760 OR NH SR
Inductive
Resonance

10. Aldehydes Aldehydes slightly higher freq. than methyl ketones C-H bend
760
C(O)-H stretch
2825, 2720
C=O stretch 1724

11. overtone band
combination bands

12. Carboxylic Acids Broad OH absorption due to H-bonding 3300-2500
C=O stretch near 1760 ( aliphatic monomer)
reduced to (aliphatic dimers)
intramolecular H-bonding is usually stronger
C=O stretch can be reduced to 1680

13. Acid Halide C-H stretch 3065 C=O stretch 1774 Fermi Resonance
overtone of 872

14. Esters
C=O stretch
1765
O-C=C asymmetric
stretch 1193
C-H stretches

15. Amines N-H Stretch (as) 3372, (ss) 3290 N-H wag 900-700 N-H Bend 1617
C-N stretch 1073
octylamine
Aliphatic C-H bands

16. Nitriles
CºN stretch 2226
Aromatic C-H bands

17. IR of Benzylthiol S-H Bend Aromatic overtones 2565 Aliphatic C-H bands
Aromatic C-H bands

18. IR of p-toluenesulfonate
S=O stretch
1355, 1177
S-C-O
stretch

19. Sample 1a

20. Solution Band at 2200 suggests CºC bands at 3300 suggest H-CºC
bands around 3000 aliphatic C-H
one possibility:
C3H3Cl

21. Sample 1b

22. Solution High frequency bands suggest aromatic C-H and aliphatic C-H
bands around 1600 suggest substituted aromatic
one possibility:
C10H14

23. Sample 1c

24. Solution High frequency bands suggest N-H, aromatic C-H
and aliphatic C-H
bands around 1600 suggest substituted aromatic
one possibility:
C7H9N

25. Sample 1d

26. Solution High frequency bands suggest O-H, aromatic C-H
and aliphatic C-H
bands around 1600 suggest substituted aromatic
one possibility:
C7H8O

27. Sample 1e

28. Solution High frequency bands suggest N-H, aromatic C-H
and aliphatic C-H
Note: N-H band is sharp…
bands around 1600 suggest substituted aromatic
one possibility:
C8H11N

29. Sample 1f

30. Solution High frequency bands suggest aromatic C-H and aliphatic C-H
bands around 1600 suggest substituted aromatic
one possibility:
C7H7Cl

31. Sample 1g

32. Solution High frequency bands suggest H-bonding and O-H
and aliphatic C-H
O2 suggest acid? But band at 1728 suggests strong
C=O ….perhaps inductive effect of Cl
one possibility:
C3H5O2Cl

33. Sample 1h

34. Solution High frequency bands suggest H-bonding and O-H
and aliphatic C-H
O suggest alcohol?
Note: no unsaturation
one possibility:
C5H12O

35. Sample 1i

36. Solution High frequency bands suggest aliphatic C-H
band at 1718 suggests ketone
band at 1650 suggest some unsaturation
one possibility:
C6H10O

37. Sample 1j

38. Solution High frequency bands suggest aromatic and aliphatic C-H
bands at suggest aromatic
one possibility:
C10H12

39. Sample 1k

40. Solution High frequency bands suggest aliphatic C-H
bands at 2300 suggest CN
second N; note no evidence of N-H
one possibility:
C5H10N2