JEE Main · 2017 · 02 Apr 2017 · Offline · Aldehydes Ketones and Carboxylic Acids

The correct sequence of reagents for the following conversion will be :

(A) $[Ag (NH_{3})_{2}]^{+} OH^{-}, H^{+} / CH_{3} OH$ , $CH_{3} MgBr$ ✓ Correct
(B) $CH_{3} MgBr, H^{+} / CH_{3} OH$ , $[Ag (NH_{3})_{2}]^{+} OH^{-}$
(C) $CH_{3} MgBr, [Ag (NH_{3})_{2}]^{+} OH^{-}, H^{+} / CH_{3} OH$
(D) $[Ag (NH_{3})_{2}]^{+} OH^{-}, CH_{3} MgBr, H^{+} / CH_{3} OH$

Answer: (A)

Solution

Read the target backwards. The aldehyde must first be lifted to a carboxylic acid, and Tollens' reagent

[Ag (NH X_{3}) X_{2}] X^{+} OH X^{-}

does exactly that oxidation. The acid is then esterified with

H X^{+} / CH X_{3} OH

, and finally

CH X_{3} MgBr

attacks the ester to install the new carbon framework. So the order runs Tollens' first, esterification next, Grignard last. Running the Grignard at the outset would be hopeless — the acidic

- COOH

- OH

protons would simply destroy it.

JEE Main · 2017 · 02 Apr 2017 · Offline · Single correct option

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JEE Main · 2017 · 02 Apr 2017 · Offline · Aldehydes Ketones and Carboxylic Acids

Solution

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