$\underset{\left(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{Cl}_{2}\right)}{\mathrm{A}} \xrightarrow[373 \mathrm{~K}]{\text { Hydrolysis }}\underset{\left(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}\right)}{\mathrm{B}}$ B reacts with Hydroxyl amine but does not give Tollen's test. Identify A and B.

(D) 2,2 - Dichlorobutane and Butan - 2 - one

(A) 1, 1 - Dichlorobutane and Butanal

(B) 2,2 - Dichlorobutane and Butanal

(C) 1, 1- Dichlorobutane and 2 - Butanone

JEE Main · 2021 · 26 Feb 2021 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

(C_{4} H_{8} Cl_{2}) A Hydrolysis 373 K (C_{4} H_{8} O) B

B reacts with Hydroxyl amine but does not give Tollen's test. Identify A and B.

(A)1, 1 - Dichlorobutane and Butanal
(B)2,2 - Dichlorobutane and Butanal
(C)1, 1- Dichlorobutane and 2 - Butanone
(D)2,2 - Dichlorobutane and Butan - 2 - one✓ Correct

Answer: (D)

Solution

Hydrolysis of a geminal dihalide at

373

K replaces the two halogens held on one carbon by a single oxygen, so B carries a carbonyl group. B adds hydroxylamine, which confirms the carbonyl, but it fails Tollens' test, so B is a ketone and not an aldehyde.
A ketone of formula

C_{4} H_{8} O

demands the carbonyl carbon inside the chain, so both chlorine atoms of

C_{4} H_{8} C l_{2}

must sit on the second carbon of a straight four carbon chain:

C H_{3} CC l_{2} C H_{2} C H_{3} H_{2} O, 373 K C H_{3} COC H_{2} C H_{3}

A is 2,2-dichlorobutane and B is butan-2-one.

JEE Main · 2021 · 26 Feb 2021 · Shift 1 · Single correct option

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JEE Main · 2021 · 26 Feb 2021 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

Solution

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