Which of the following statements relating to the acidic character of alcohols is not true?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Alcohols behave as electrophiles.
Alcohols are Brönsted acids: they can donate the proton of the O–H group to a strong base and form alkoxide ions (e.g. with sodium they give RONa and \( \ce{H2} \)). Their acidic character comes from the polar O–H bond, and it is affected by groups that change the electron density on oxygen.
\( \displaystyle \ce{2R-OH + 2Na -> 2R-ONa + H2 ^} \)
Option (1) It is due to the polar nature of OH bond. — True of the acidic character of alcohols. Oxygen is more electronegative than hydrogen, so the shared pair is pulled towards O and the H can leave as \( \ce{H^+} \).
Option (2) Increases with an attachment of e− withdrawing group. — True of the acidic character of alcohols. An electron-withdrawing group pulls electron density away from oxygen, which increases the polarity of O–H and stabilises the alkoxide ion. Electron-releasing alkyl groups do the opposite, so acidity falls in the order 1° > 2° > 3°.
Option (3) Alcohols are weaker acids than water. — True of the acidic character of alcohols. The alkyl group pushes electrons towards oxygen and destabilises the alkoxide ion. So water is the better proton donor, and it takes the proton back from an alkoxide:
\( \displaystyle \ce{R-O^-Na^+ + H2O -> R-OH + NaOH} \)
Option (4) Alcohols behave as electrophiles. — Not true of the acidic character of alcohols. Alcohols do react as electrophiles in some reactions, but then the C–O bond breaks (a protonated alcohol loses water). In acidic behaviour the O–H bond breaks and the alcohol gives up \( \ce{H^+} \) as a proton donor, so acting as an electrophile is not part of its acidic character.
NCERT (2026-27 edition):
Acidity of Alcohols and Phenols – “… (ii) Acidity of alcohols: The acidic character of alcohols is due to the polar nature of O–H bond. An electron-releasing group (–CH3, –C2H5) increases electron density on oxygen tending to decrease the polarity of O-H bond. This decreases the acid strength. … Alcohols are, however, weaker acids than water. This can be illustrated by the reaction of water with an alkoxide.”
Chemical Reactions – “Alcohols are versatile compounds. They react both as nucleophiles and electrophiles. The bond between O–H is broken when alcohols react as nucleophiles. … The bond between C–O is broken when they react as electrophiles. Protonated alcohols react in this manner.”