Table 1. Frequencies (in cm–1) and Assignments of Important Vibrations of 25-OH.
| observed
frequency (cm–1) |
|||
|---|---|---|---|
| scaled frequencya (cm–1) | ATR-IR (bulk sample) | PM-IRRAS (monolayer) | description of the vibration |
| 1017 | 1021 | 1016–1020 | rings deformation |
| 1035 | 1040 | 1035–1045 | C(3)—O stretching, C—C—C scissoring in rings |
| 1054 | 1054 | 1054 (at 20 mN/m) | C—O—H scissoring (both) |
| 1068 | rings deformation; CH2 twisting in rings | ||
| 1073 | 1077–1082 | ||
| 1116 | 1009 | 1009 | C(25)—O—H scissoring; CH2 rocking; C—C—C scissoring at the end of the chain |
| 1140 | 1141 | 141 (at 10 mN/m) | CH2 twisting; rings deformation |
| 1164 | 1158 | 1167–1170 | CH2 twisting; C=C—C scissoring; rings deformation |
| 1196 | 1195 | 1192 | C(25)—O stretching |
| 1231 | 1233 | 1232 | CH2 wagging in chain |
| 1277 | 1277 | 1272 | C(3)—O—H scissoring; CH2 wagging in rings |
| 1310 | 1316 | 1310–1316 | C(25)—O—H scissoring |
| 1335 | 1333 | C(25)—O—H scissoring; CH2 wagging in chain | |
| 1351 | 1362 | 1350 | CH3 scissoring |
| 1371 | 1376 | 1378–1383 | |
| 1425 | CH2 scissoring | ||
| 1433 (∥) | 1437 | 1440 | |
| 1457 (⊥) | 1460 | ||
| 1465 (⊥) | 1468 | 1464 | |
| 1470 (⊥) | 1480 | ||
| 2865 (∥) | 2863 | 2858–2861 | CH stretching |
| 2873 (⊥) | |||
| 2906 (⊥) | 2902 | 2901–2905 | CH2 symmetric stretching |
| 2925 (⊥) | 2923 | 2921–2926 | |
| 2942 (⊥) | 2943 | 2946 | |
| 2968 (⊥) | 2963 | 2961 | CH2 assymmetric stretching in tail |
| 2980 (∥) | 2976 | 2982 | CH2 assymmetric stretching |
a
(∥) or (⊥) symbols refer to the predicted orientation of the dipole moment vector with respect to the long axis of the 25-OH molecule.