Question

Describe the characteristic infrared absorption frequencies that would allow you to distinguish between the pairs:

butanamide and pentan-3-one

Answer 1

Solution.

The structures of butanamide and pentan-3-one are given below:

     

Characteristic IR absorption frequencies of the functional groups are:

1. Pentan-3-one:

C=O stretch 1670-1820 cm^-1 ; strong.

2. Butanamide:

C=O stretch 1640-1690 cm^-1 ; strong.

butanamide N-H bending 1550-1640; medium.

butanamide N-H stretch 3100-3500 cm^-1 ; medium - this frequency will allow you to distinguish between the pairs.