Which one is the example of Allylic halide?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 3-bromocyclohex-1-ene
An allylic halide has the halogen on an sp3 carbon atom next to a C=C double bond, that is, on an allylic carbon. The simplest example is allyl bromide, \( \ce{CH2=CH-CH2Br} \). It differs from a vinylic halide, where the halogen is on a carbon of the double bond itself, and from an aryl halide, where the halogen is on a benzene ring.
In the structure of Option (3), 3-bromocyclohex-1-ene, the bromine atom is on a ring carbon that is not part of the double bond but is bonded to one of its carbon atoms. That carbon is sp3 hybridised and allylic, so this compound is the allylic halide.
Why the other options are incorrect
Option (1) bromobenzene — Incorrect. Br is bonded directly to an sp2 carbon of a benzene ring, so it is an aryl halide.
Option (2) 1-bromocyclohex-1-ene — Incorrect. Br is on one of the two carbon atoms of the ring double bond, so it is a vinylic halide.
Option (4) \(CH_2=CHBr\) — Incorrect. Vinyl bromide has Br on a carbon of the C=C bond; it is the simplest vinylic halide.
NCERT (2026-27 edition):
Allylic Halides
