Question

In electrophilic substitution reaction nitrobenzene is:
A. Meta-directing
B. Ortho-directing
C. Para-directing
D. Not reactive and does not undergo any substitution

Answer 1

Hint: The substituents in the benzene ring can be classified as activating and deactivating groups. The activating groups are electron-donating whereas deactivating groups are electron-withdrawing groups. The activating groups favour ortho and para positions in the benzene ring whereas deactivating groups favour meta-position in the benzene ring.

Complete step by step answer:
It is known that benzene is an electron-rich compound because of its double bond and it tends to attract electron-deficient species. Electrophiles are the species that can accept electron pairs from other compounds and therefore, it acts as the electron acceptor. In benzene, an additional reaction is very difficult and almost impossible in the benzene ring since addition tends to break the delocalization of electrons in the benzene ring, and thus, it affects the stability of benzene. Thus, substitution is possible and favours in the benzene ring.
In nitrobenzene, it is known that the nitro group is an electron-withdrawing species, and therefore, it comes under the category of deactivating species. Thus, it favours meta-position for the upcoming substitution in benzene ring since deactivating groups have higher electron density in meta position than ortho and para position.
Thus, the electrophilic substitution reaction for nitrobenzene is meta-directing.

So, the correct answer is Option A.

Note: Generally, the activating group increases the rate of electrophilic substitution in the benzene ring since it increases the electron density of the benzene ring. The well-known example for activating groups is methyl (or) alkyl group, amine, alcohol group, etc. The deactivating group decreases the rate of electrophilic substitution in the benzene ring since it decreases the electron density of the benzene ring. The well-known example of deactivating groups is carbonyl group, nitro, ester, pyridine, and cyanide group, etc.