Alcohols behave as:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Both (2) and (3)
A Bronsted acid donates a proton and a Bronsted base accepts one. An alcohol can do both.
As a Bronsted acid: the polar O–H bond lets an alcohol give its proton to a stronger base, for example to sodium metal:
\( \displaystyle \ce{2R-OH + 2Na -> 2R-ONa + H2} \)
The alcohol loses \( \ce{H^+} \) and forms a sodium alkoxide with hydrogen gas.
As a Bronsted base: the unshared electron pairs on oxygen accept a proton from a strong acid:
\( \displaystyle \ce{R-OH + H^+ -> R-OH2^+} \)
The alcohol gains \( \ce{H^+} \) and forms a protonated alcohol.
Why the other options are incorrect
Option (1) Lewis acids — Incorrect. A Lewis acid accepts an electron pair. The oxygen of an alcohol has lone pairs to donate, so an alcohol behaves as a Lewis base, not a Lewis acid.
NCERT (2026-27 edition):
Acidity of alcohols and phenols – “… In fact, alcohols and phenols are Brönsted acids i.e., they can donate a proton to a stronger base (B:).”
“… Alcohols act as Bronsted bases as well. It is due to the presence of unshared electron pairs on oxygen, which makes them proton acceptors.”