Question

Which of the following compounds does not react with \[{C_6}{H_5}S{O_2}Cl\]
A) ${C_2}{H_5} - N{H_2}$
B) $C{H_3} - N{H_2}$
C) ${\left( {C{H_3}} \right)_2}NH$
D) ${\left( {{C_2}{H_5}} \right)_3}N$

Answer 1

Hint: The above mentioned reagent \[{C_6}{H_5}S{O_2}Cl\]
 is chemically called Benzene sulphonyl chloride. It is also called Hinsberg's reagent. It is an organosulfur compound. This reagent is mainly used to detect the presence of primary, secondary and tertiary amines. It reacts with the compounds having N-H and O-H bonds.

Complete answer:
As I already mentioned, it can react with the compounds having N-H bonds. It means, this reagent can react with primary and secondary amines but not tertiary amines because both primary and secondary amines have N-H bond whereas the tertiary amine does not contain free hydrogen in the amine group to donate electrons to the sulphur present in Hinsberg’s reagent. Now, in order to find out the answer, let us check which of the above mentioned options has tertiary amine. The structure of the primary amine is \[R - N{H_2}\]% where ‘R’ can be any alkyl or aryl group. The first two compounds are primary amines and hence can react with the reagent.. The structure of secondary amine is R-NH, the compound given in the third option has a structure similar to secondary amine and it also reacts with the reagent. The last compound is a tertiary amine having the structure R-N, and cannot react with the reagent.

So the correct option is D

Note:
Hinsberg’s test is mainly done to distinguish the amines. In this test, the given amine is shaken with the reagent in the presence of NaOH or KOH, if it forms soluble sulfonamide salt, then it is primary amine, if it forms insoluble sulfonamide salt, then it is secondary amide and if no salt is formed, it is said to be tertiary amine.