The figure shows primary, secondary and tertiary benzylic alcohols.
What is the hybridisation of the carbon atom that carries the –OH group, and of the ring carbon atom to which it is attached, respectively?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → sp3 and sp2
A carbon with four single bonds is sp3; a carbon that is part of a double bond or of the benzene ring is sp2.
Carbon carrying –OH — sp3. In each structure this carbon (CH2OH, or the coloured C with OH) has four single bonds: to OH, to the ring and to H or C groups.
Ring carbon attached to it — sp2. It belongs to the benzene ring, whose carbons are joined by alternate double bonds.
Why the other options are incorrect
Option (1) sp2 and sp2 — Incorrect. –OH on an sp2 ring carbon would make a phenol, not a benzylic alcohol.
Option (3) sp3 and sp3 — Incorrect. The ring carbon is part of the aromatic ring, so it is not sp3.
Option (4) sp2 and sp3 — Incorrect. This reverses the two carbons: the carbon carrying –OH has only single bonds, and the ring carbon is part of the benzene ring.
NCERT (2026-27 edition):
7.1.1 Alcohols— Mono, Di, Tri or Polyhydric alcohols – “Benzylic alcohols: In these alcohols, the —OH group is attached to a sp3—hybridised carbon atom next to an aromatic ring.”
7.3 Structures of Functional Groups – “In phenols, the –OH group is attached to sp2 hybridised carbon of an aromatic ring.”
Primary, secondary and tertiary benzylic alcohols (7.1.1)