Concept:An allylic halide contains a halogen atom bonded to an
sp3 carbon that is directly adjacent to a carbon‑carbon double bond.
Explanation:The allylic position is the saturated carbon next to the double bond.
Option A:
CH3−CH2−CH2−X — there is no double bond, so it is not allylic.
Option B:
C6H5−CH2−X — the halogen is attached to the carbon next to a benzene ring, making it a benzyl halide, not an allylic halide.
Option C:
CH2=CH−CH2−X — the
CH2 group bearing X is adjacent to the double bond, so this is an allylic halide.
Option D:
CH3−CH=CH−X — the halogen is directly attached to an
sp2 double‑bond carbon, so this is a vinylic halide.
Answer:Option C:
CH2=CH−CH2−X.