ir ranges

Alcohol O–H

3500–3000 cm⁻¹, broad

Phenol O–H

3500–2800 cm⁻¹, very broad

Carboxylic acid O–H

3500–2500 cm⁻¹, extremely broad

N–H (amines/amides)

3400–3100 cm⁻¹, sharper than O–H

sp C–H (alkyne)

~3300 cm⁻¹, sharp

sp² C–H (alkene/aromatic)

3150–3000 cm⁻¹

sp³ C–H (alkane)

3000–2850 cm⁻1

C≡C (alkyne)

~2250 cm⁻¹

C≡N (nitrile)

~2250 cm⁻¹, strong

General C=O stretch

1850–1650 cm⁻¹, strong

Acid chloride C=O

1800–1850 cm⁻¹

Anhydride C=O

Two peaks ~1820 and ~1760 cm⁻¹

Ester C=O

~1750 cm⁻¹

Carboxylic acid C=O

~1710 cm⁻¹, must also see broad O–H

Aldehyde C=O

~1720 cm⁻¹

Ketone C=O

~1700 cm⁻¹

Amide C=O

~1650 cm⁻¹, must also see N–H

Aldehyde C–H

Two weak peaks at 2750–2850 cm⁻¹

Alkene C=C

1650–1450 cm⁻¹

Aromatic C=C

~1600 and ~1500 cm⁻¹