Characteristic Infrared Absorptions

C-H
Stretching Vibrations
GroupRange, cm-1Intensity*
Alkanes2962 - 2853m - s
Alkenes3090 - 3010m
Alkynesca. 3300s
Aromaticsca. 3030v
NCH3, OCH32850 - 2700m
CHO2900 - 2820 and 2775 - 2700w - m
Bending Vibrations
GroupRange, cm-1Intensity*
CHca. 1340w
CH21485 - 1445m
CH31470 - 1430 and 1380 - 1370s
C(CH3)21385 - 1380 and 1370 - 1365s
C(CH3)31395 - 1385 and ca. 1365s
Aromatics  
5 adj H750 and 700v, s
O-H
Stretching Vibrations
GroupRange, cm-1Intensity*
Free O-H3650 - 3590v, sh
H-bonded3550 - 3200b
Bending Vibrations
GroupRange, cm-1Intensity*
Alcohols1430 - 1280b, m
Phenols1390 - 1310m
Carboxylic acids1440 - 1400m
N-H
Stretching Vibrations
GroupRange, cm-1Intensity*
Primary amine, free3500 - 3300 and 3420 - 3250m - s
Secondary amine3500 - 3310m
Bending Vibrations
GroupRange, cm-1Intensity*
 1650 - 1550w - s
C=O
Stretching Vibrations
GroupRange, cm-1Intensity*
Ketones, aldehydes, carboxylic acidsca. 1750 - 1660s
Acyl halides1850 - 1750s
Amidesca. 1710 - 1620s
C=N
Stretching Vibrations
Range, cm-1Intensity*
1690 - 1630v
C≡N
Stretching Vibrations
Range, cm-1Intensity*
2260 - 2220m
C=C
Stretching Vibrations
Range, cm-1Intensity*
1690 - 1560w
C≡C
Stretching Vibrations
Range, cm-1Intensity*
2275 - 2100w - m
Car-Car
 Range, cm-1Intensity*
Skeletal vibrationsca. 1600w - m
in aromatics1580, 1500, 1450 
C-O-C, C-O-H
Stretching Vibrations
GroupRange, cm-1Intensity*
Esthersca. 1100 
Esthers: aliphatic1280 - 1220s
Esthers: alkyl, aryl1050 - 1000 
Esters1290 - 1180b, s
Bending Vibrations
GroupRange, cm-1Intensity*
Alcohols1430 - 1280m
Phenols1390 - 1310m - s
C-X, X is a halogen
Stretching Vibrations
GroupRange, cm-1Intensity*
Fluorides1400 - 1000s
Chlorides800 - 600s
Bromides625 - 400s
Iodides625 - 400s

* 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.