Q. Total number of alkali insoluble solid sulphonamides obtained by reaction of given amines with Hinsberg's reagent is ______.

Aniline, N-Methylaniline, Methanamine, N,N-Dimethylmethanamine, N-Methyl methanamine, Phenylmethanamine, N-propylaniline, N-phenylaniline, N,N-Dimethylaniline, Allyl amine, Isopropyl amine

Correct Answer: 4

Solution

In the Hinsberg test:

Primary amines form sulphonamides soluble in alkali due to presence of acidic N–H.

Secondary amines form sulphonamides that are alkali insoluble solids.

Tertiary amines do not react with Hinsberg’s reagent.

Now classify the given amines:

Aniline – Primary Methanamine – Primary N-Methyl methanamine – Primary Phenylmethanamine – Primary Allyl amine – Primary Isopropyl amine – Primary

N-Methylaniline – Secondary N-propylaniline – Secondary N-phenylaniline – Secondary N,N-Dimethylaniline – Tertiary N,N-Dimethylmethanamine – Tertiary

Only secondary amines give alkali insoluble solid sulphonamides.

Number of secondary amines = 4

Hence, the correct answer is 4.

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