The reaction of diazonium salt with aniline yields p-aminoazobenzene. It is an example of which of the following reaction?

Question

Accepted Answer

The reaction of diazonium salt with aniline to yield p-aminoazobenzene is an example of an electrophilic substitution reaction. Here's a detailed explanation supporting why Option 4 is correct and why the other options are incorrect:

1. **Why Option 4 is Correct (Electrophilic Substitution):**
   - In this reaction, the diazonium salt acts as an electrophile. An electrophile is a species that seeks electrons and can accept an electron pair. Aniline, which contains an amino group (-NH2), is a nucleophile due to the lone pair of electrons on the nitrogen atom.
   - The reaction involves the diazonium ion (from the diazonium salt) attacking the aniline molecule. The nitrogen of the diazonium ion forms a bond with the para position of the aniline ring, resulting in the formation of p-aminoazobenzene.
   - This process is characteristic of electrophilic substitution, where an electrophile replaces a hydrogen atom in an aromatic ring.

2. **Why the Other Options are Incorrect:**
   - **Option 1 (Addition Reaction):** Addition reactions typically involve the addition of atoms or groups to a molecule without the loss of any atom. In the case of the reaction between diazonium salt and aniline, a new bond is formed at the para position of the aromatic ring, but it involves substitution rather than simple addition.
   - **Option 2 (Nucleophilic Substitution):** Nucleophilic substitution involves a nucleophile replacing a leaving group in a molecule. In this reaction, the diazonium ion is the electrophile, not the nucleophile, and it is not replacing a leaving group in the aniline molecule.
   - **Option 3 (Electrophilic Addition):** Electrophilic addition typically occurs in reactions involving alkenes or alkynes, where an electrophile adds across a double or triple bond. The reaction in question involves an aromatic ring, which undergoes substitution rather than addition.

In summary, the reaction of diazonium salt with aniline to form p-aminoazobenzene is best described as an electrophilic substitution reaction, making Option 4 the correct choice.