Toluene on chlorination in presence of UV light gives

The correct answer is Option (2) → Benzal Chloride

Chlorine reacts with toluene in two different ways, depending on the conditions. In the dark with a Lewis acid (\( \ce{FeCl3} \)), chlorine substitutes on the ring, at the ortho and para positions. In UV light (or at the boiling point) without a catalyst, chlorine atoms (free radicals) are formed, and they substitute the hydrogens of the methyl side chain one after another:

    \( \displaystyle \ce{C6H5CH3} \xrightarrow[h\nu]{\ce{Cl2}} \ce{C6H5CH2Cl} \xrightarrow[h\nu]{\ce{Cl2}} \ce{C6H5CHCl2} \xrightarrow[h\nu]{\ce{Cl2}} \ce{C6H5CCl3} \)

The products are benzyl chloride, benzal chloride and benzotrichloride, each step also giving HCl. Side chain chlorination of toluene to benzal chloride, followed by hydrolysis, is the commercial method of making benzaldehyde:

    \( \displaystyle \ce{C6H5CHCl2} \xrightarrow[373\ \mathrm{K}]{\ce{H2O}} \ce{C6H5CHO + 2HCl} \)

Why the other options are incorrect

• Option (1) Benzoyl Chloride — Incorrect. Benzoyl chloride, \( \ce{C6H5COCl} \), is an acid chloride; it contains a C=O group and is made from benzoic acid with \( \ce{SOCl2} \) or \( \ce{PCl5} \). Chlorine only replaces hydrogen atoms of the side chain; it cannot introduce oxygen.

• Option (3) p- Chlorotoluene — Incorrect. Ring substitution at the para position needs a Lewis acid catalyst (\( \ce{FeCl3} \)) in the dark, not UV light.

• Option (4) o-Chlorotoluene — Incorrect. This is the other ring product of chlorination with \( \ce{FeCl3} \) in the dark; it is not formed by free-radical side chain chlorination.

Note: In the original NTA paper, Option (1) was printed as “Benzyl Chloride”. Benzyl chloride is also formed in this reaction: it is the first product of side chain chlorination, and with a limited amount of chlorine it is the main product, so that option was also correct. It has been changed to “Benzoyl Chloride” so that students are not confused and the question has a single answer.

NCERT (2026-27 edition):
By Side Chain Chlorination Followed by Hydrolysis