Question

When benzene diazonium chloride reacts with N, N - dimethyl aniline at ice cold condition gives:
A. p - aminoazobenzene
B. Diazoaminobenzene
C. p - dimethyl aminoazobenzene
D. p - dimethylaminoazobenzene

Answer 1

This reaction is an example of the coupling reactions that take place in nitrogen containing organic compounds and results in the formation of a chemical indicator called Methyl Yellow.

Complete step by step answer:

Let us first look into benzene diazonium chloride as a compound and observe its structure before moving onto this specific reaction in particular.
Diazonium ions are always present in solutions of compounds such as benzenediazonium chloride and contain an $-{{N}_{2}}^{+}$ group in their chemical structure and formula. Taking benzenediazonium chloride as an example, here the diazonium ion is attached to a benzene ring, which results in the overall compound looking as follows:

In most reactions of the diazonium ion, the $-{{N}_{2}}^{+}$ group is replaced by a substituted group of some kind with the nitrogen being released into the atmosphere as nitrogen gas.
However, let us now look at its coupling reaction with N,N-dimethylaniline.
The reaction in question results in the formation of an azo dye named Methyl Yellow whose chemical name is p – dimethyl aminoazobenzene that is often used as a very popular acid base indicator in most chemical laboratories from around the world.

Thus, the answer to this question is ‘C.

Note: Remember that Methyl yellow is an organic compound with the formula ${{C}_{6}}{{H}_{5}}{{N}_{2}}{{C}_{6}}{{H}_{4}}N{{(C{{H}_{3}})}_{2}}$. It is an azo dye derived from the reaction of dimethylaniline with benzenediazonium halide. Due to it being an azo dye compound, it is expected to display bright colours in its physical structure, which is clearly observed since it is a yellow solid. It is used as a dye for plastics and can also be used as a pH indicator.