Question

Is nitrobenzene more reactive than benzoic acid for electrophilic substitution?

Answer 1

We know that both nitro and carboxylic acids groups when attached to a benzene ring pull away the electron density from the ring towards themselves or in other words are powerful electron withdrawing groups but their relative withdrawing strengths decides their reactivity.

Complete Step By Step Answer:
Nitrobenzene is benzene attached to the nitro functional group and benzoic acid is benzene attached to the carboxylic acid group. Both these groups have a tendency to withdraw electron density from the ring towards them through electronic effects like inductive effect and resonance effect.
The $- R$ and $- I$ effect of nitro group and carboxylic acid group makes them powerful electron withdrawing groups.
Benzene ring is a rich source of electrons due to the cyclic conjugation of double bonds inside it and therefore shows electrophilic substitution reactions where electron deficient groups attack the benzene ring. In order to be more reactive towards electrophilic substitution reaction, the benzene rings must be attached to functional groups that add to the electron density of the ring and make it more electrophilic.
Both nitro and carboxylic acid groups act in the opposite direction and reduce the reactivity of the benzene ring towards electrophilic substitution. But the electron withdrawing strength of nitro group is higher than that of carboxylic acid group $( - N{O_2}) > ( - COOH)$ due to which nitrobenzene would be even less reactive than benzoic acid.
$\Rightarrow$ Therefore the answer is No, the nitrobenzene ring is not more reactive than benzoic acid towards electrophilic substitution reaction.

Note:
In order to make benzene rings more electrophilic and electron rich in nature, groups like hydroxyl group, amine group, methyl substituent should be attached that add to the electron density through electronic effects like resonance and hyperconjugation.