Consider the following statements about the classification of monohydric alcohols.
(A) In allylic alcohols, the –OH group is attached to an sp3 hybridised carbon adjacent to the carbon–carbon double bond.
(B) In benzylic alcohols, the –OH group is attached to an sp2 hybridised carbon atom of the aromatic ring.
(C) Allylic and benzylic alcohols may be primary, secondary or tertiary.
(D) In vinylic alcohols, the –OH group is bonded to a carbon–carbon double bond, as in CH2=CH–OH.
Which of the statements given above are correct? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (C) and (D) only
Monohydric alcohols are classified by the hybridisation of the carbon atom that carries the –OH group. Allylic and benzylic alcohols have the –OH on an sp3 carbon; vinylic alcohols have it on an sp2 carbon.
(A) In allylic alcohols, the –OH group is attached to an sp3 hybridised carbon adjacent to the carbon–carbon double bond. — True. This carbon is the allylic carbon, as in CH2=CH–CH2OH.
(B) In benzylic alcohols, the –OH group is attached to an sp2 hybridised carbon atom of the aromatic ring. — False. In a benzylic alcohol the –OH is on an sp3 carbon next to the ring, as in C6H5CH2OH. An –OH on a ring carbon would make the compound a phenol.
(C) Allylic and benzylic alcohols may be primary, secondary or tertiary. — True. The sp3 carbon carrying –OH may hold one, two or three carbon groups, for example CH2=CH–CH2OH (primary) and C6H5CH(OH)CH3 (secondary).
(D) In vinylic alcohols, the –OH group is bonded to a carbon–carbon double bond, as in CH2=CH–OH. — True. The –OH is on a vinylic carbon, which is sp2 hybridised; these are the alcohols with a Csp2–OH bond.
NCERT (2026-27 edition):
7.1.1 Alcohols— Mono, Di, Tri or Polyhydric alcohols – “Allylic alcohols: In these alcohols, the —OH group is attached to a sp3 hybridised carbon adjacent to the carbon-carbon double bond, that is to an allylic carbon.”
“Benzylic alcohols: In these alcohols, the —OH group is attached to a sp3—hybridised carbon atom next to an aromatic ring.”
“Allylic and benzylic alcohols may be primary, secondary or tertiary.”
“(ii) Compounds containing Csp2−OH bond: These alcohols contain —OH group bonded to a carbon-carbon double bond, i.e., to a vinylic carbon or to an aryl carbon. These alcohols are also known as vinylic alcohols. Vinylic alcohol: CH2 = CH – OH”