Characteristic Infrared Absorptions
- C-H
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Stretching Vibrations Group Range, cm-1 Intensity* Alkanes 2962 - 2853 m - s Alkenes 3090 - 3010 m Alkynes ca. 3300 s Aromatics ca. 3030 v NCH3, OCH3 2850 - 2700 m CHO 2900 - 2820 and 2775 - 2700 w - m Bending Vibrations Group Range, cm-1 Intensity* CH ca. 1340 w CH2 1485 - 1445 m CH3 1470 - 1430 and 1380 - 1370 s C(CH3)2 1385 - 1380 and 1370 - 1365 s C(CH3)3 1395 - 1385 and ca. 1365 s Aromatics 5 adj H 750 and 700 v, s - O-H
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Stretching Vibrations Group Range, cm-1 Intensity* Free O-H 3650 - 3590 v, sh H-bonded 3550 - 3200 b Bending Vibrations Group Range, cm-1 Intensity* Alcohols 1430 - 1280 b, m Phenols 1390 - 1310 m Carboxylic acids 1440 - 1400 m - N-H
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Stretching Vibrations Group Range, cm-1 Intensity* Primary amine, free 3500 - 3300 and 3420 - 3250 m - s Secondary amine 3500 - 3310 m Bending Vibrations Group Range, cm-1 Intensity* 1650 - 1550 w - s - C=O
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Stretching Vibrations Group Range, cm-1 Intensity* Ketones, aldehydes, carboxylic acids ca. 1750 - 1660 s Acyl halides 1850 - 1750 s Amides ca. 1710 - 1620 s - C=N
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Stretching Vibrations Range, cm-1 Intensity* 1690 - 1630 v - C≡N
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Stretching Vibrations Range, cm-1 Intensity* 2260 - 2220 m - C=C
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Stretching Vibrations Range, cm-1 Intensity* 1690 - 1560 w - C≡C
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Stretching Vibrations Range, cm-1 Intensity* 2275 - 2100 w - m - Car-Car
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Range, cm-1 Intensity* Skeletal vibrations ca. 1600 w - m in aromatics 1580, 1500, 1450 - C-O-C, C-O-H
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Stretching Vibrations Group Range, cm-1 Intensity* Esthers ca. 1100 Esthers: aliphatic 1280 - 1220 s Esthers: alkyl, aryl 1050 - 1000 Esters 1290 - 1180 b, s Bending Vibrations Group Range, cm-1 Intensity* Alcohols 1430 - 1280 m Phenols 1390 - 1310 m - s - C-X, X is a halogen
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Stretching Vibrations Group Range, cm-1 Intensity* Fluorides 1400 - 1000 s Chlorides 800 - 600 s Bromides 625 - 400 s Iodides 625 - 400 s
* v = variable; sh = sharp; b = broad; w = weak; m = medium; s = strong
Reference: R.M. Silverstein, G.C. Bassler, and T.C. Morrill, "Spectrometric Identification of Organic Compounds," 5th ed., Wiley, NY, 199l, pps. 158-164.