Read the Passage carefully and answer the Questions.
Carbonyl compounds such as aldehydes, ketones, and carboxylic acids play an important role in the biochemical process of plants and animal kingdom. Many aldehydes and ketones find applications in dye, perfumery and other industries. The carbonyl carbon atom is \( sp^2 \)-hybridized forming three sigma and one pi-bond with oxygen. C-O bonds are polar bond due to high electronegativity of oxygen than carbon. Hence the carbonyl carbon behaves as an electrophilic center and oxygen as a nucleophilic centre. Primary and secondary alcohols yield aldehydes and ketones respectively upon oxidation with variety of oxidizing agents. The boiling points of aldehydes and ketones differ from hydrocarbons and ethers. Aldehydes and ketones undergo nucleophilic addition reaction due to presence of electrophilic carbonyl carbon. Nucleophile and a proton add across the carbon oxygen double bond.
The starting compound Y in the following reaction is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( \ce{RCH2OH} \)
A compound that is oxidised first to an aldehyde and then to a carboxylic acid must be a primary alcohol. Its \( \ce{-CH2OH} \) carbon has two hydrogens: losing one H from carbon (with the H of the O–H group) gives \( \ce{-CHO} \), and the aldehyde has one more H on that carbon, which is replaced by –OH in the second oxidation:
\( \displaystyle \ce{RCH2OH} \xrightarrow{[\ce{O}]} \ce{RCHO} \xrightarrow{[\ce{O}]} \ce{RCOOH} \)
So Y is \( \ce{RCH2OH} \). A secondary alcohol stops at a ketone, and a tertiary alcohol is not oxidised at all.
Why the other options are incorrect
Option (1) \( \ce{RCH2COOH} \) — Incorrect. This is already a carboxylic acid, the last stage of the oxidation; it does not give an aldehyde on oxidation.
Option (2) \( \ce{RCH=CHOH} \) — Incorrect. This is an enol, which is unstable and changes by tautomerism into the aldehyde \( \ce{RCH2CHO} \); the change is a rearrangement, not an oxidation.
Option (4) \( \ce{RCH2CH3} \) — Incorrect. An alkane has no functional group that common oxidising agents convert into an aldehyde.
NCERT (2026-27 edition):
Oxidation
