IK

Functional Group Names

Absorption Ranges(cm-1)

Type of Vibration

[Look for a single absorption

&

causing IR absorption

Example compounds

in these regions, unless stated otherwise.]

Alkanes:

3000-2800

H-C-H Asymmetric &

Symmetric Stretch

H

(Note: The absorptions can be seen as several

H

H

distinct peaks in this region.)

C

Methane

1500-1440

H-C-H Bend

H

Alkenes:

3100-3000

C=C-H Asymmetric

Stretch

H

H

1-Propene

1675-1600

C-C=C Symmetric

H3C

C

Stretch

H

Alkynes:

3300-3200

C

H Stretch

2200-2100

C

C

Stretch

HC

C

CH3

Propyne

Aromatic Rings:

3100-3000

C=C-H Asymmetric

H

Stretch

H

C

H

1600-1580

C-C=C Symmetric

C

C

Benzene

Stretch

H C

C C H

1500-1450

C-C=C Asymmetric

H

Stretch

Phenols & Alcohols:

3600-3100

Hydrogen-bonded O-H

H

Stretch

H H

H

OH

OH

C

C

C

C

(This peak usually appears much

(Note: Phenols MUST have

broader than the other IR

C

C

H

H

C

H

Methanol

Aromatic Ring Absorptions too.)

absorptions.

H

(Alcohol)

Phenol

Carboxylic Acids:

3400-2400

Hydrogen-bonded O-H

O

(This peak always covers the entire

Stretch

region with a VERY BROAD peak.)

[Note: This peak can obscure

Formic Acid

H C OH

other peaks in this region.]

1730-1650

C=O Stretch

Ketones:

O

1750-1625

C=O Stretch

Acetone

H C

C

CH

3

3

Aldehydes:

1750-1625

C=O Stretch

O

2850-2800

C-H Stretch off C=O

Ethanal

H3C C

H

2750-2700

C-H Stretch off C=O

Functional Group Names

Absorption Ranges(cm-1)

Type of Vibration

[Look for a single absorption

&

causing IR absorption

Example compounds

in these regions, unless stated otherwise.]

Esters:

1755-1650

C=O Stretch

O

H C O CH3

Methyl Formate

(1300-1000)

(C-O Stretch)

Ethers:

(1300-1000)

(C-O Stretch)

O

Diethyl Ether

(aka-Ethyl Ether)

Amines—Primary:

3500-3100

N-H Stretch

H

Ethylamine

(TWO PEAKS!)

N

1640-1560

N-H Bend

H

Amines—Secondary:

3500-3100

N-H Stretch

(ONE PEAK!)

CH3

N-Methylethylamine

N

1550-1450

N-H Bend

H

Nitriles:

H

N Methanenitrile

2300-2200

H C

C

C

N Stretch

H

Nitro Groups:

1600-1500

N=O Stretch

O

+

Nitromethane

H C N

O

3

(Note: Both peaks are <200 cm-1 apart.)

1400-1300

N=O Bend

Amides:

3500-3100

N-H Stretch (similar to amines)

O

1670-1600

C=O Stretch

Methanamide

H C C

NH

2

3

1640-1550

N-H Bend