Characteristic IR Band Positions | Group | Frequency Range (cm-1) | | OH stretching vibrations | | | Free OH | 3610-3645 (sharp) | | Intramolecular H bonds | 3450-3600 (sharp) | | Intermolecular H Bonds | 3200-3550 (broad) | | Chelate Compounds | 2500-3200 (very broad) | | NH Stretching vibrations | | | Free NH | 3300-3500 | | H bonded NH | 3070-3350 | | CH Stretching vibrations | | | =-C-H | 3280-3340 | | =C-H | 3000-3100 | | C-CH3 | 2862-2882, 2652-2972 | | O-CH3 | 2815-2832 | | N-CH3 (aromatic) | 2810-2820 | | N-CH3 (aliphatic) | 2780-2805 | | CH2 | 2843-2863,2916-2936 | | CH | 2880-2900 | | SH Stretching Vibrations | | | Free SH | 2550-2600 | | C=-N Stretching Vibrations | | | Nonconjugated | 2240-2260 | | Conjugated | 2215-2240 | | C=-C Stretching Vibrations | | | C=-CH (terminal) | 2100-2140 | | C-C=-C-C | 2190-2260 | | C-C=-C-C=-CH | 2040-2200 | | C=O Stretching Vibrations | | | Nonconjugated | 1700-1900 | | Conjugated | 1590-1750 | | Amides | ~1650 | | C=C Sretching Vibrations | | | Nonconjugated | 1620-1680 | | Conjugated | 1585-1625 | | CH Bending Vibrations | | | CH2 | 1405-1465 | | CH3 | 1355-1395, 1430-1470 | | C-O-C Vibrations in Esters | | | Formates | ~1175 | | Acetates | ~1240, 1010-1040 | | Benzoates | ~1275 | | C-OH Stretching Vibrations | | | Secondary Cyclic Alcohols | 990-1060 | | CH out-of-plane bending vibrations in substituted ethylenic systems | | | -CH=CH2 | 905-915, 985-995 | | -CH=CH-(cis) | 650-750 | | -CH=CH-(trans) | 960-970 | | C=CH2 | 885-895 | | | | |
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