A compound (X) containing C, H and O does not react with sodium. It also does not reduce Tollens’ reagent. On heating with an excess of hydroiodic acid (HI), (X) gives only one organic product (Y). On hydrolysis, (Y) gives a new compound (Z), which can be converted back into (Y) by reaction with red phosphorus and iodine. On oxidation with potassium permanganate, (Z) gives a monocarboxylic acid whose molar mass is 60 g mol−1.
What is the compound (Z)?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Ethanol
A primary alcohol is oxidised by potassium permanganate to the carboxylic acid with the same number of carbon atoms. So (Z) is found from the acid it gives.
The acid: a monocarboxylic acid CnH2n+1COOH has molar mass 14n + 46; 14n + 46 = 60 gives n = 1, so the acid is \( \ce{CH3COOH} \) (ethanoic acid).
Compound (Z): the two-carbon primary alcohol that gives it is ethanol:
\( \displaystyle \ce{CH3CH2OH + 2[O]} \xrightarrow{\ce{KMnO4}} \ce{CH3COOH + H2O} \)
NCERT (2026-27 edition):
8.7 Methods of Preparation of Carboxylic Acids – “1. From primary alcohols and aldehydes
Primary alcohols are readily oxidised to carboxylic acids with common oxidising agents such as potassium permanganate (KMnO4) in neutral, acidic or alkaline media or by potassium dichromate (K2Cr2O7) and chromium trioxide (CrO3) in acidic media (Jones reagent).”