Q68P alpha- Amino acids can be prepar... [FREE SOLUTION]

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Chapter 21: Q68P (page 1028)

alpha- Amino acids can be prepared by treating an aldehyde with ammonia/trace acid, followed by hydrogen cyanide, followed by acid-catalyzed hydrolysis.
a. Draw the structures of the two intermediates formed in this reaction.
b. What amino acid is formed when the aldehyde that is used is 3-methylbutanal?
c. What aldehyde is needed to prepare isoleucine?

Short Answer

Expert verified

b. The amino acid formed when the aldehyde used is 3-methylbutanal is leucine.

c. The aldehyde needed to prepare isoleucine is 2-methylbutanal.

Step by step solution

Strecker synthesis

Stecker synthesis is a method used to synthesize amino acids by treating the given aldehyde with ammonia and trace acid, followed by hydrogen cyanide and acid hydrolysis.

In this method, aldehyde reacts with ammonia in the presence of acid to form an imine. This further reacts with hydrogen cyanide to form alpha-amino cyanide. The hydrolysis of this product produces aplha-amino acids.

Structures of the intermediates formed in the reaction and the aldehyde needed for isoleucine

The reaction for the synthesis of -amino acids is given below.

The intermediates of the reaction are given below.

b. Amino acids are formed from Strecker synthesis. The side chain (R-group) of the amino acid depends only on the aldehyde used. The product formed is given below.

Hence, the amino acid formed when the aldehyde used is 3-methylbutanal is leucine.

c. The aldehyde, 2-methylbutanal reacts with ammonia and trace acid to form isoleucine. Hence, the aldehyde used for this reaction is 2-methylbutanal. The reaction is given below.