JEE Main · 2021 · 27 Aug 2021 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

Given below are two statements:
Statement I: Ethyl pent-4-yn-oate on reaction with

CH_{3} MgBr

gives a

3^{\circ}

-alcohol.
Statement II: In this reaction one mole of ethyl pent-4-yn-oate utilizes two moles of

CH_{3} MgBr

.
In the light of the above statements, choose the most appropriate answer from the options given below.

(A)Both Statement I and Statement II are false.
(B)Both Statement I and Statement II are true.
(C)Statement I is false but Statement II is true.
(D)Statement I is true but Statement II is false.✓ Correct

Answer: (D)

Solution

Ethyl pent-4-ynoate,

HC \equiv C - C H_{2} C H_{2} - COO C_{2} H_{5}

, carries both an ester group and an acidic terminal alkynic hydrogen. One equivalent of

C H_{3} MgBr

is spent merely in deprotonating the

\equiv C - H

, while the ester reacts with two further equivalents: the first gives a ketone and the second adds to it, so after work-up a tertiary alcohol bearing two methyl groups results. A

3^{\circ}

alcohol is indeed formed, but three moles of the reagent are needed, not two. Statement I is true and Statement II is false.

JEE Main · 2021 · 27 Aug 2021 · Shift 2 · Single correct option

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JEE Main · 2021 · 27 Aug 2021 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

Solution

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