Question

Assertion: A reaction between a diazo salt and an aromatic amine or a phenol, giving amino-azo compound is called coupling reaction. Because
Reason: Condensation of diazonium with phenol is carried out in a weakly acidic medium.
A) Both assertion and reason are correct and reason is the correct explanation for assertion.
B) Both assertion and reason are correct but reason is not the correct explanation for assertion.
C) Assertion is correct but reason is incorrect.
D) Both assertion and reason are incorrect.

Answer 1

The answer to this question here is based on the fact that coupling reactions involve the combining of two rings through $-N=N-$ bond and the product formed here is the coloured compound.

Complete step by step answer:
We have come across the concepts of making a dye and some of the coloured compounds by the well known reaction that is the coupling reaction of diazonium salts.
Now, let us see what actually the coupling reaction is and what happens in it which helps us to approach the required answer.
- Coupling reaction by the name itself says coupling of two rings which is defined in general as two the reaction in which fragments are joined together with the aid of metal catalyst.
- In coupling reaction, there is a common intermediate where the energy is transferred from one side of reaction to the other side.
- Azo coupling is the one where diazonium compounds and the other aromatic compounds produce an azo compound. It is an electrophilic aromatic substitution reaction where the aryl diazonium cation acts as the electrophile and the nucleophile is the activated arene.
- The reaction of benzene diazonium chloride of simply diazonium reacts with phenol in the basic medium and not the acidic medium and therefore the reason is incorrect here but the assertion is true.

Therefore, the correct answer to this question is option C. Assertion is correct but reason is incorrect.

Note: Note that the coupling reaction releases energy because of the ATP hydrolysis and thus this is used as the fuel for some other process and this reaction is important in cells for the hydrolysis of ATP and this redox reaction of enzyme is responsible for the colour change of protein heme – group.