CBSE Class 12 Chemistry Notes: Biomolecules – Chemical Properties of Amino Acids

Chemical Properties

Amino acids show the following characteristic reactions.

1. Reaction of the carboxyl group.

2. Reaction of the amino group.

3. Reaction involving both the carboxyl and the amino group.

Reaction of the carboxyl group

Reaction with base 

(i)

(ii)

Mechanism:

Esterification

Note: HCl first converts the dipolar ion into an acid which is subsequently esterified.

Decarboxylation

Reduction

Reaction with strong acid

Reaction with Nitrous acid 

Note: (i)   This reaction forms the basis of the “van slyke method” for the estimation of amino acids.

(ii)   The nitrogen is evolved (one half comes from the amino acid) quantitatively and its volume measured.

Reaction with Nitrosyl halide

Reaction with 2, 4 – Dintrofluorobenzene (DNFB)

Reaction involving both the carboxyl & the amino group

Effect of heat

α – amino acids undergo dehydration on heating (200°C) to give diketo piperazines.

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