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.
To which class of compounds does (X) belong?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Ether
An ether (R–O–R) has no O–H bond and no C=O group, and its C–O bond is cleaved by an excess of HI on heating. The clues on (X) fit this:
No reaction with sodium: (X) has no –OH group.
Does not reduce Tollens’ reagent: (X) is not an aldehyde.
Excess HI gives only one product (Y): both alkyl groups are the same, so (X) is a symmetrical dialkyl ether.
Acid of molar mass 60 g mol−1: this is \( \ce{CH3COOH} \) (24 + 4 + 32 = 60), so (Z) is ethanol, (Y) is ethyl iodide and (X) is ethoxyethane (diethyl ether).
\( \displaystyle \ce{C2H5-O-C2H5 + 2HI} \xrightarrow{\Delta} \ce{2C2H5I + H2O} \)
The C–O bonds of the ether break, and each ethyl group ends up as ethyl iodide.
Why the other options are incorrect
Option (1) Carboxylic acid — Incorrect. A carboxylic acid has an acidic –COOH group and reacts with sodium to give hydrogen; (X) does not.
Option (2) Aldehyde — Incorrect. An aldehyde is easily oxidised and reduces Tollens’ reagent to a silver mirror; (X) does not.
Option (3) Alcohol — Incorrect. An alcohol has an –OH group and reacts with sodium to give an alkoxide and hydrogen; (X) does not.
NCERT (2026-27 edition):
7.6.3 Chemical Reactions – “Ethers are the least reactive of the functional groups. The cleavage of C-O bond in ethers takes place under drastic conditions with excess of hydrogen halides. The reaction of dialkyl ether gives two alkyl halide molecules.”