IR Spectrsoscopy

1700, narrow & strong

C=O standard

3400, broad

O-H standard

1400-600

Fingerprint region

4000-1400

Functional Group Region

• additive effect of multiple bonds in a compound

• increased bond polarity

Factors that affect intensity

• mass of atoms in bond vibration

• bond strength

Factors that affect wavenumbers

1720

C=O of aldehyde/ketone

1650

C=O of amide

1740 (withdrawal strengthens = character)

C=O of ester/carboxylic acid

broad band 3600-3300

O-H bond of an alcohol with H-bonding

super broad band 3200-2500

O-H bond of a carboxylic acid with dimer H-bonding

Broad band with point for each N-H, 3400

*1600 bend band for primary amines

N-H bond

1050

C-O bond ether

1250

C-O bond carboxylic acid

1050 AND 1250

C-O bond ester

2200

C

||| bond

C

1600

C=C bond

2950

C-H sp3

3150

C-H sp2

3300

C-H sp

2 bands: 2820 and 2720

C-H aldehyde

*1600: Primary amine bend

1650: C=C bond

1650: C=O amide (N donation decreases = character)

1700: C=O ketone

1720: C=O aldehyde (slight withdrawal from H)

1740: C=O carboxylic acid/ester (withdrawal from O increases = character)

Double bond region: around 1700

pointed 3400: N-H (1 point = 2*, 2 points = 1*)

broad 3600-3300: alcohol O-H

broad 2500-3200: carboxylic acid O-H

3300: sp3 C-H

3150: sp2 C-H

2950: sp C-H

2850 & 2750: Aldehyde C-H

O-H/N-H, C-H region: around 3300

2200

C

||| region

C

1050: C-O ether

1250: C-O carboxylic acid

1050 & 1250: ester

C-O bond region: around 1100

1600 & 1430-1500 sharp bands

Benzene ring

To the right of 1400

Methyl group (sp3 with 3 bonded hydrogens)

1550

N-H bond