Question

Which of the following is not the usual method for preparation of primary amine?
A. Hofmann’s method
B. Curtius reaction
C. Schmidt reaction
D. Friedel-craft reaction

Answer 1

Hint: Primary amine can be formed when one hydrogen atom of ammonia is replaced by alkyl group or any aryl group such as RNH₂ where R can be an aromatic group or any alkyl group.

Complete Step by Step Solution:
Primary amine (1°) can be prepared by Hofmann reaction when primary amide react with aqueous solution of sodium hydroxide or potassium hydroxide and bromide and thus, give suitable primary amine such as

Curtius reaction or Curtius degradation is also helpful to prepare primary amine. To prepare primary amine from this reaction, acyl azide undergoes thermal decomposition to give isocyanate after losing N₂. Then isocyanate is made to react with nucleophile H₂O to give primary amine such as


Primary amine can also be prepared from Schmidt reactions. This is quite a simple and sorted method. In this reaction carboxylic acid derivatives react with azide group in the presence of acidic condition (H⁺ ion) to give suitable primary amine with the release of nitrogen and Carbon dioxide such as


Whereas Friedel-crafts reaction is not a suitable method to prepare primary amine. Friedel-crafts reaction is only used for preparation of alkyl benzene or acetophenone.
Thus, the correct answer is D, as Friedel-crafts reaction is not the usual method for preparation of primary amine.

Note: Friedel-crafts reaction is only used to attached substituents on aromatic rings. There are two types of Friedel-crafts reaction one is alkylation and acylation reaction. In alkylation reaction alkyl groups are substitutes and acylation reaction acyl group substitutes.