Question

Which of the following test will be used to distinguish between methylamine and dimethylamine:

• A. Carbylamine test
• B. Liebermann nitroamine test
• C. Liebermann nitroso test
• D. Hinsberg reaction test

Answer 1

Answer: (A)

Carbylamine reaction mechanism includes the addition of an amine to the intermediate created from the dehydrohalogenation of chloroform. This intermediate is called dichlorocarbene. The carbylamine reaction is also known as Hofmann isocyanide synthesis.

It is the reaction of a primary amine, chloroform and a base to synthesize isocyanides. The dichlorocarbene intermediate is very important for this conversion. The carbylamine reaction cannot be used to synthesize isocyanides from secondary or tertiary amines. In general, the carbylamine reaction can be written as –

R-NH${}_2$ + CHCl${}_3$ + 3KOH $\to$ RNC (Carbylamine) + 3KCl + 3H${}_2$O

Methylamine is a primary amine and dimethylamine and secondary amine. Hence, these two can be distinguished by carbylamine test

Hence, the correct option is $\text{A}$