JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

An organic compound (X) with molecular formula

C_{3} H_{6} O

is not readily oxidised. On reduction it gives (

C_{3} H_{8} O (Y)

which reacts with HBr to give a bromide (Z) which is converted to Grignard reagent. This Grinard reagent on reaction with (X) followed by hydrolysis give 2,3-dimethylbutan-2-ol. Compounds (X), (Y) and (Z) respectively are :

(A) $CH_{3} COCH_{3}, CH_{3} CH_{2} CH_{2} OH, CH_{3} CH (Br) CH_{3}$
(B) $CH_{3} COCH_{3}, CH_{3} CH (OH) CH_{3}, CH_{3} CH (Br) CH_{3}$ ✓ Correct
(C) $CH_{3} CH_{2} CHO, CH_{3} CH_{2} CH_{2} OH, CH_{3} CH_{2} CH_{2} Br$
(D) $CH_{3} CH_{2} CHO, CH_{3} CH = CH_{2}, CH_{3} CH (Br) CH_{3}$

Answer: (B)

Solution

C_{3} H_{6} O

compound that resists ready oxidation is the ketone acetone rather than an aldehyde, so

X

C H_{3} COC H_{3}

. Its reduction gives propan-2-ol,

Y = C H_{3} CH (OH) C H_{3}

, which reacts with

HBr

to give 2-bromopropane,

Z = C H_{3} CHBrC H_{3}

. The Grignard reagent from

Z

, isopropylmagnesium bromide, adds to the carbonyl of acetone and on hydrolysis furnishes

(C H_{3})_{2} C (OH) CH (C H_{3})_{2}

, 2,3-dimethylbutan-2-ol. The compounds are thus

X = C H_{3} COC H_{3}

Y = C H_{3} CH (OH) C H_{3}

and

Z = C H_{3} CHBrC H_{3}

JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Single correct option

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JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

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