Principal diagnostic bands are in boldface.
| Class, functional group | Group frequency (cm-1) | Relative absorption intensity |
|---|---|---|
| Alkanes, alkyl groups C-H stretch C-H bend |
2980-2850 1470-1450, 1400- 1360 |
medium to strong medium |
| Alkenes =C-H stretch C=C stretch |
3090-3010 1680-1620 |
medium very weak (trans) to medium (cis,term) |
| Alkynes ≡C-H stretch C≡C stretch |
3300-3250 2250-2200 |
medium, (terminal alkynes only) weak (internal) to medium (terminal) |
| Aromatics C-H stretch arom. C-C stretch | 3100-3000 1630-1590, 1520-1480 |
medium medium |
| Alcohols O-H stretch C-O stretch |
3650-3300 1150-1030 |
strong, broad strong |
| Amines N-H stretch |
3450-3280 | weak to medium, broad |
| Ethers C-O stretch |
1140-1100 | very strong |
| Aldehydes "C-H stretch" C=O stretch |
2740-2720 1735-1720 |
medium very strong |
| Ketones C=O stretch |
1725-1705 | very strong |
| Carboxylic acids O-H stretch C=O stretch |
3300-2400 1710-1680 |
strong, very broad very strong |
| Carboxylic acid chlorides C=O stretch |
1810-1790 | strong |
| Esters C=O stretch C-O-C stretch |
1750-1735 1290-1180 |
very strong very strong |
| Amides N-H stretch C=O stretch |
3540-3380 1680-1640 |
medium, broad (prim. & sec. only) very strong |
| Nitriles C≡N stretch |
2260-2240 | weak |