Important IR Stretches

sp³ C-H (alkanes)

<3000

sp² C-H

>3000

C (triple bond) C

2100-2260

C (triple bond) N

2220-2260

N-H

3300

sp C-H

3300

O-H (alcohol)

3300 (st, broad)

O-H (carboxylic acid)

3300 - 2700 (covers up about 1/3 of the graph)

Aldehyde C-H

*2700-2850* (doesn't need to be double peaked like in the picture)

C-O (generic)

1050

C-O-C (ester)

1250 & 1050 (st, broad)

CH₃ umbrella

1385

Geminal dimethyl (a carbon attached to two methyl groups)

1385 (doublet)

C=C (conjugated)

1620-1640

C=C (isolated)

1640-1680

C=O (amide)

1640-1700

C=O (ketone/acid)

1700-1725

Benzene

1700-2000 (wiggle waggle)

C=O (aldehyde)

1720-1740

C=O (ester)

1730-1750

C=O (acid halide/anhydride)

1760-1860

C=C (aromatic)

around 1600