Which of the following is the correct statement about coupling reaction of diazonium salts?

Options

A. In coupling reactions, diazonium ion works as a nucleophile
B. Coupling takes place almost exclusively at the ortho position with aniline and phenol
C. Coupling with phenol and aniline is most rapid in slightly acidic medium
D. Coupling with phenol is most rapid in slightly basic medium

Answer

D

Explanation

In coupling reactions, diazonium ion substitutes benzene ring by electrophilic substitution mechanism, so it works as an electrophile. In slightly basic conditions, phenol is in deprotonated form, due to which it is more reactive. However, on increasing basicity, hydroxide ions oxidize diazonium ions and coupling would not occur. Slightly acidic conditions favour diazonium ion.s concentration, but below pH=5 aniline gets protonated and becomes unreactive.