Alcohols can be prepared in many ways. They are prepared from alkenes by acid-catalysed hydration and by hydroboration–oxidation. Alcohols are also prepared from aldehydes and ketones by reduction. The reduction of carboxylic acids and esters also gives alcohols. Alcohols are produced by the reaction of Grignard reagents with aldehydes and ketones. Phenol, also known as carbolic acid, was first isolated in the early nineteenth century from coal tar. Nowadays, phenol is commercially produced synthetically. In the laboratory, phenols are prepared from benzene derivatives in many ways.
Propanone, on reaction with an alkylmagnesium bromide followed by hydrolysis, gives a:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Tertiary alcohol
A Grignard reagent adds to the carbonyl group (nucleophilic addition): its alkyl group bonds to the carbonyl carbon and the oxygen takes MgBr. Hydrolysis of this adduct gives the alcohol.
\( \displaystyle \ce{(CH3)2C=O + RMgBr -> (CH3)2C(R)-OMgBr} \)
\( \displaystyle \ce{(CH3)2C(R)-OMgBr + H2O -> (CH3)2C(R)-OH + Mg(OH)Br} \)
The carbonyl carbon of propanone already carries two CH3 groups; after the R group adds, the carbon bearing –OH is bonded to three carbon atoms, so the product is a tertiary alcohol. Every ketone gives a tertiary alcohol in this way.
Why the other options are incorrect
Option (1) Primary alcohol — Incorrect. A primary alcohol is formed only with methanal, whose carbonyl carbon carries no alkyl group.
Option (2) Secondary alcohol — Incorrect. A secondary alcohol is formed with other aldehydes (one alkyl group on the carbonyl carbon), not with a ketone.
Option (4) Carboxylic acid — Incorrect. A Grignard reagent gives a carboxylic acid with carbon dioxide, not with a ketone.
NCERT (2026-27 edition):
7.4.1 Preparation of Alcohols – “3. From Grignard reagents
Alcohols are produced by the reaction of Grignard reagents (Unit 6, Class XII) with aldehydes and ketones.”
“You will notice that the reaction produces … tertiary alcohol with ketones.”