Question

The electrophilic aromatic substitution of a compound ${C_6}{H_5}Y$ produces mainly a meta-disubstituted product. Among the following, which one could be the substituent Y?
A.$- N{H_2}$
B.$- COOH$
C.$- C{H_3}$
D.$- OC{H_3}$

Answer 1

The aromatic compounds undergo substitution reactions like electrophilic substitution and nucleophilic substitution reactions. The incoming electrophile attacking position can be directed by the substituents present on the aromatic compound. Electron withdrawing groups make the incoming electrophile to be meta directed.

Complete answer:
Aromatic compounds are the compounds that are cyclic, planar, conjugation of $\pi$ electrons and obeying Huckel’s rule. Huckel's rule is given by the condition of $\left( {4n + 2} \right)\pi$ electrons, where n is a whole number.
Given the compound is ${C_6}{H_5}Y$ , it is an aromatic compound. There is a substituent Y on benzene ring. Thus, the compound is a derivative of benzene. Benzene and its derivatives are aromatic compounds.
The given compound undergoes electrophilic aromatic substitution. The presence of Y makes the incoming electrophile attack. If the substituent is electron withdrawing then it makes the incoming electrophile to be meta directed.
In the given options amine group, methyl group and methoxy groups are electron releasing groups. These all groups direct the incoming electrophile to ortho and para positions.
Acid group is an electron withdrawing group and directs the incoming electrophile to meta direction.
Thus, $- COOH$is the substituent on ${C_6}{H_5}Y$.
Hence option B is the correct one.

Note:
As the aromatic compounds involve resonance with the substituent on them. The electron withdrawing groups makes the compound have negative charge at meta position, which leads to the direction of incoming electrophile to meta position.