Question

why low temperature is required for diazotization reaction

Answer 1

During diazotization and coupling reactions we have to maintain a low temperature because at high temperature diazonium salts forms other by products and give phenol by reacting with water at high temperature which would lead to a large error in your experiments.

The reaction is as follows:

Step1: In this step para-nitroaniline is reacted with sodium nitrite and hydrochloride and gives para-nitrobenzene diazonium chloride as follows: