Read the passage carefully and answer the Questions.
Aldehydes, carboxylic acids and ketones are widespread in the animal and plant kingdoms. They play a pivotal role in various biochemical processes of life. Their presence in nature adds fragrance and flavor. These compounds are widely used in food products, pharmaceuticals, paints, resins and other important product industries. These compounds are prepared by various laboratory methods, which mainly include oxidation, formylation, acylation and reduction. Due to the polar nature of the carbonyl group in aldehydes and ketones, they can exhibit different reactions like nucleophilic addition. They do exhibit redox and various condensation reactions which lead to the formation of various important compounds. On the other hand, the carboxylic acids are mainly prepared by oxidation and hydrolysis of different compounds. The carboxylic acid consists of a carbonyl group and the hydroxy group (attached to the carbonyl carbon atom). This makes it possible for the carboxylic acid to participate in various chemical reactions which involve cleavage of the C-OH bond and the O-H bond along with the reactions involving the complete -COOH group.
Propyne on hydration in presence of mercury ions produce
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Acetone
Alkynes add water in the presence of dilute sulphuric acid and mercury(II) sulphate. The addition follows Markovnikov’s rule: the –OH goes to the carbon with fewer hydrogens. The product is first an enol, which is unstable and changes (tautomerises) into the carbonyl compound. Ethyne gives ethanal; every other alkyne gives a ketone.
For propyne, the –OH adds to C-2:
\( \displaystyle \ce{CH3-C#CH + H2O} \xrightarrow[\text{333 K}]{\ce{Hg^2+}/\ce{H2SO4}} \ce{CH3-C(OH)=CH2} \)
\( \displaystyle \ce{CH3-C(OH)=CH2 <=> CH3-CO-CH3} \)
So propyne gives propanone, that is, acetone.
Why the other options are incorrect
Option (2) Propanal — Incorrect. It would need anti-Markovnikov addition (the –OH at C-1), which happens in hydroboration-oxidation, not in the mercury-catalysed hydration.
Option (3) 1-Propanol — Incorrect. Hydration of an alkyne ends at the carbonyl stage; a saturated alcohol comes from hydration of an alkene (anti-Markovnikov here) or reduction of a carbonyl compound.
Option (4) Propan-2-ol — Incorrect. This is the product of acid-catalysed hydration of propene; propyne stops at the ketone.
NCERT (2026-27 edition):
By Hydration of Alkynes
