Typical IR Absorption Frequencies For Common Functional Groups

Bond Functional Group Frequency in cm−1 (Intensity*)
C‐H Alkane 3000–2850 (s)
‐CH3 1450 and 1375 (m)
‐CH2− 1465 (m)
Alkene 3100–3000 (m), 1000–650 (s)
Aromatic 3100–3050 (s), 900–690 (s)
Alkyne (terminal) 3300 (s)
Aldehyde 2850 and 2750 (w)
C=C Alkene 1630 (w–m)
Aromatic 1600–1475 (w–m)
C‐C Alkyne 2150–2100 (w–m)
C=O Aldehyde 1740–1720 (s)
Ketone 1725–1705 (s)
Carboxylic Acid 1730–1700 (s)
Ester 1750–1730 (s)
Amide 1670–1640 (s)
Anhydride 1810 and 1760 (s)
Acid Chloride 1800 (s)
C‐O Alcohol, Ether, Ester, Carboxylic Acid, Anhydride 1300–1000 (s)
O‐H Alcohol, Phenol
Free 3650–3600 (m)
Hydrogen‐bonded 3500–3200 (m)
Carboxylic Acids 3300–2400 (m)
N‐H Primary and Secondary Amine and Amide 3550–3060 (m–s); 1640–1550 (m–s)
C‐N Amine 1250–1000 (m–s)
C=N Imine and Oxime 1690–1640 (w–s)
C=N Nitrile 2260–2240 (m)
N=O Nitro (R‐NO2) 1550 and 1350 (s)
C‐Cl Chloride 800–600 (s)

s = strong; m = medium; w = weak