The reaction of toluene with \(Cl_2\) in the presence of \(FeCl_3\) gives \(X\) and the reaction in the presence of light gives \(Y\). Thus, \(X\) and \(Y\) are:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \(X\) = o and p-Chlorotoluene, \(Y=\) trichloromethylbenzene
The conditions decide where chlorine enters toluene:
Cl2 with FeCl3 (Lewis acid, in the dark) — electrophilic substitution in the ring. The \( \ce{CH3} \) group is ortho, para-directing, so X is a mixture of o-chlorotoluene and p-chlorotoluene.
Cl2 in light (or on heating) — free radical substitution in the side chain. The H atoms of \( \ce{CH3} \) are replaced one after another: \( \ce{C6H5CH2Cl} \) (benzyl chloride) → \( \ce{C6H5CHCl2} \) (benzal chloride) → \( \ce{C6H5CCl3} \). With enough chlorine, Y is trichloromethylbenzene (benzotrichloride).
\( \ce{C6H5CH3} \) + \( \ce{Cl2} \) (\( \ce{FeCl3} \), dark) → o- and p-\( \ce{ClC6H4CH3} \) + HCl
\( \ce{C6H5CH3} \) + \( \ce{3Cl2} \) (light) → \( \ce{C6H5CCl3} \) + 3HCl
Why the other options are incorrect
Option (1) X = Benzyl chloride, Y = m-Chlorotoluene — Incorrect. The two conditions are swapped; \( \ce{FeCl3} \) does not chlorinate the side chain, and light does not give ring substitution (nor would \( \ce{CH3} \) direct to meta).
Option (2) X = Benzyl chloride, Y = o-Chlorotoluene — Incorrect. Again the conditions are swapped: benzyl chloride comes from chlorination in light, o-chlorotoluene from \( \ce{Cl2} \)/\( \ce{FeCl3} \).
Option (3) X = m-Chlorotoluene, Y = p-Chlorotoluene — Incorrect. \( \ce{CH3} \) is ortho, para-directing, so m-chlorotoluene is not the product, and in light the side chain, not the ring, is chlorinated.
NCERT (2026-27 edition):
Preparation of Haloarenes – “… Aryl chlorides and bromides can be easily prepared by electrophilic substitution of arenes with chlorine and bromine respectively in the presence of Lewis acid catalysts like iron or iron(III) chloride. The ortho and para isomers can be easily separated due to large difference in their melting points.”
Preparation of Aldehydes – “… Side chain chlorination of toluene gives benzal chloride, which on hydrolysis gives benzaldehyde. This is a commercial method of manufacture of benzaldehyde.”