Tertiary alcohols do not undergo oxidation under ordinary conditions. Which of the following explains this?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → The carbon atom carrying the –OH group has no hydrogen atom that can be lost to form a C=O bond.
In the oxidation of an alcohol, a carbon-oxygen double bond is formed by the loss of the H of the O–H group and an H from the carbon that carries the –OH group.
A primary carbon (–CH2OH) has two such hydrogens and a secondary carbon (>CHOH) has one, but in a tertiary alcohol, R3C–OH, that carbon carries three alkyl groups and no hydrogen. So no C=O can form on it.
Only under strong conditions, such as KMnO4 at elevated temperatures, are C–C bonds broken, giving a mixture of carboxylic acids with fewer carbon atoms.
Why the other options are incorrect
Option (1) Tertiary alcohols form the most stable carbocations. — Incorrect.
The fact is true, and it explains why tertiary alcohols react fastest with HCl and are dehydrated most easily.
In oxidation, however, only the O–H and C–H bonds are broken; the C–O bond stays, no carbocation is formed, and so its stability has no part in the result.
Option (3) Tertiary alcohols are stronger acids than primary alcohols. — Incorrect. The acid strength of alcohols falls in the order primary > secondary > tertiary, so tertiary alcohols are the weakest acids.
Option (4) The C–O bond of a tertiary alcohol is too strong to be broken. — Incorrect. The C–O bond of a tertiary alcohol breaks most easily: in the Lucas test it gives turbidity at once, and the C–O bond is not broken in oxidation anyway.
NCERT (2026-27 edition):
7.4.4 Chemical Reactions – “4. Oxidation: Oxidation of alcohols involves the formation of a carbon- oxygen double bond with cleavage of an O-H and C-H bonds.”
“Tertiary alcohols do not undergo oxidation reaction. Under strong reaction conditions such as strong oxidising agents (KMnO4) and elevated temperatures, cleavage of various C-C bonds takes place and a mixture of carboxylic acids containing lesser number of carbon atoms is formed.”