Identify the allyl chloride from the following:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 3-chlorocyclopentene
Halogen compounds are classified by the carbon that carries the halogen. In an allylic halide, the halogen is bonded to an sp3 carbon next to a C=C double bond (the allylic carbon). In a vinylic halide it is on a doubly bonded carbon itself, and in a benzylic halide it is on an sp3 carbon attached to a benzene ring.
In Option (3) the chlorine is on the ring carbon right next to the C=C bond of cyclopentene, so it is an allylic chloride.
Why the other options are incorrect
Option (1) benzyl chloride — Incorrect. The \( \ce{CH2Cl} \) carbon is attached to a benzene ring, so it is a benzylic halide.
Option (2) a chlorocycloheptene — Incorrect. The carbon carrying Cl is not next to the double bond, so it is an ordinary secondary alkyl halide.
Option (4) a vinylic chloride — Incorrect. The chlorine is on a carbon that is itself part of the C=C bond, so it is a vinylic halide.
NCERT (2026-27 edition):
Allylic Halides
