Question

Which of the following can be used to distinguish between primary and secondary amines?
A.Hinsberg test
B.Lucas test
C.Isocyanide test
D.Victor Meyer's test

Answer 1

Hint: Primary and secondary amines have specific distinct properties about them, such as their characteristic odour. Aliphatic amines are known to be less dense than water and have stronger bonds of ammonia compared to the aromatic amines.

Complete answer:
- Amines are classified as primary, secondary, or tertiary by the number of carbons bonded to the nitrogen atom.
- Primary amine has one carbon bonded to the nitrogen atom. Secondary amine has two carbons bonded to the nitrogen, and tertiary amine has three carbons bonded to the nitrogen.
- Hinsberg test and Isocyanide test are used to distinguish between primary and secondary amines.
- In the Hinsberg test, the given amine is to be shaken well along with Hinsberg reagent in the presence of an aqueous alkali, which can be either sodium hydroxide or potassium hydroxide. The amines are treated with benzene sulfonyl chloride. Amines act as nucleophiles which attack the electrophile sulfonyl chloride.
- Isocyanide test is also known as Saytzeff’s Isocyanide test. In this reaction, the analyte is heated with alcoholic potassium hydroxide and chloroform. If a primary amine is present, the isocyanides formed, as indicated by a foul odour.

Hence, the answer to the question is (A) and (C).

Note:
Isocyanide test is always given by primary amines, it is not given by secondary or tertiary amines. Hinsberg test helps in differentiation by observing the difference in the solubility of the sulfonamide product in alkali.