Question

Explain why a diazonium group on a benzene ring cannot be used to direct an incoming substituent to the meta position.

Short answer

A diazonium group on the benzene ring cannot be used as a meta director because of the electron-withdrawing nature of the group.

Step-by-step solution

Reactions of arene diazonium salt

Aniline can be converted to arene diazonium salt by treating with nitrous acid. Nucleophiles like cyanide, bromide, and chloride replace the diazonium group if the appropriate copper(I) salt is added to the solution comprising the arene diazonium salt.

Explanation of why the diazonium group on the benzene ring cannot be used to direct an incoming substituent to the meta position.

The rate of reactions in an aromatic electrophilic substitution reaction relies upon the presence of an electron releasing or withdrawing group.

The deactivating groups tend to withdraw electron density from the benzene ring and decrease the overall reaction rate.

A diazonium ion is an electrophile due to its positive charge. The electrophilic groups tend to accept or withdraw electrons from the rest of the compound. Thus, a diazonium cation serves as an electron-withdrawing group and deactivates the aromatic ring.

The deactivated ring does not participate in the reactions, due to which the diazonium group is not used to direct an incoming substituent to the meta position.