Under identical conditions with alkaline phenol, which diazonium ion couples fastest?

Abenzenediazonium ion
B4-methylbenzenediazonium ion
C4-nitrobenzenediazonium ion
D4-methoxybenzenediazonium ion

Answer: C

Coupling is an electrophilic substitution on the phenoxide, so a more electrophilic diazonium ion reacts faster. The electron-withdrawing nitro group increases the positive character of the terminal nitrogen, while methyl and methoxy groups donate electrons and reduce it.

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