| Functional groups | Pure KHP cm−1 | KHP + 1M% cm−1 | KHP + 3M% cm−1 | KHP + 5M% cm−1 |
| C=O symmetrical stretching | 1566 | 1566 | 1565 | 1560 |
| O=C stretching | 1482 | 1484 | 1484 | 1484 |
| C-C=O stretching | 1085 | 1085 | 1085 | 1092 |
| C-H plane bend | 870 | 859 | 859 | 854 |
| O-H stretching | 3441 | 3441 | 3443 | 3452 |
| C=C asymmetric stretching | 1945 | 1942 | 1940 | 1955 |
| C=O symmetrical stretching | 441 | 454 | 444 | 447 |
| C=C stretching | 1381 | 1382 | 1381 | 1379 |