Table of Characteristic IR Absorptions
m=medium, w=weak, s=strong, n=narrow, b=broad, sh=sharp
frequency, cm
–1
bond functional group
3640–3610 (s, sh) O–H stretch, free hydroxyl alcohols, phenols
3500–3200 (s,b) O–H stretch, H–bonded alcohols, phenols
3400–3250 (m) N–H stretch 1˚, 2˚ amines, amides
3300–2500 (m) O–H stretch carboxylic acids
3330–3270 (n, s) –C
≡
C–H: C–H stretch alkynes (terminal)
3100–3000 (s) C–H stretch aromatics
3100–3000 (m) =C–H stretch alkenes
3000–2850 (m) C–H stretch alkanes
2830–2695 (m) H–C=O: C–H stretch aldehydes
2260–2210 (v) C
≡
N stretch nitriles
2260–2100 (w) –C
≡
C– stretch alkynes
1760–1665 (s) C=O stretch carbonyls (general)
1760–1690 (s) C=O stretch carboxylic acids
1750–1735 (s) C=O stretch esters, saturated aliphatic
1740–1720 (s) C=O stretch aldehydes, saturated aliphatic
1730–1715 (s) C=O stretch
α
,
β
–unsaturated esters
1715 (s) C=O stretch ketones, saturated aliphatic
1710–1665 (s) C=O stretch
α
,
β
–unsaturated aldehydes, ketones
1680–1640 (m) –C=C– stretch alkenes
1650–1580 (m) N–H bend 1˚ amines
1600–1585 (m) C–C stretch (in–ring) aromatics
1550–1475 (s) N–O asymmetric stretch nitro compounds
1500–1400 (m) C–C stretch (in–ring) aromatics
1470–1450 (m) C–H bend alkanes
1370–1350 (m) C–H rock alkanes
1360–1290 (m) N–O symmetric stretch nitro compounds
1335–1250 (s) C–N stretch aromatic amines
1320–1000 (s) C–O stretch alcohols, carboxylic acids, esters, ethers
1300–1150 (m) C–H wag (–CH
2
X) alkyl halides
1250–1020 (m) C–N stretch aliphatic amines
1000–650 (s) =C–H bend alkenes
950–910 (m) O–H bend carboxylic acids
910–665 (s, b) N–H wag 1˚, 2˚ amines
900–675 (s) C–H “oop” aromatics
850–550 (m) C–Cl stretch alkyl halides
725–720 (m) C–H rock alkanes
700–610 (b, s) –C
≡
C–H: C–H bend alkynes
690–515 (m) C–Br stretch alkyl halides
