Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: (see structure) can be easily reduced using $\mathrm{Zn}-\mathrm{Hg} / \mathrm{HCl}$ to (see structure) Reason R: $\mathrm{Zn}-\mathrm{Hg} / \mathrm{HCl}$ is used to reduce carbonyl group to $-\mathrm{CH}_{2}-$ group. In the light of the above statements, choose the correct answer from the options given below:

(B) $A$ is true but $R$ is false

(C) Both A and R are true but R is not the correct explanation of A

(D) Both A and R are true and R is the correct explanation of A

JEE Main · 2023 · 30 Jan 2023 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: (see structure) can be easily reduced using

Zn - Hg / HCl

to (see structure)
Reason R:

Zn - Hg / HCl

is used to reduce carbonyl group to

- CH_{2} -

group.
In the light of the above statements, choose the correct answer from the options given below:

(A)A is false but R is true✓ Correct
(B) $A$ is true but $R$ is false
(C)Both A and R are true but R is not the correct explanation of A
(D)Both A and R are true and R is the correct explanation of A

Answer: (A)

Solution

The reagent is that of the Clemmensen reduction, and the reason states its role correctly: zinc amalgam with hydrochloric acid turns a carbonyl group into a methylene group. The assertion, however, would apply this reduction to a molecule that also bears a tertiary hydroxyl. The medium is hot concentrated hydrochloric acid, under which a tertiary alcohol ionises readily and is lost as water or replaced by chloride, so the hydroxyl cannot survive to give the product drawn. The reason is a true statement while the assertion is false.

JEE Main · 2023 · 30 Jan 2023 · Shift 2 · Single correct option

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JEE Main · 2023 · 30 Jan 2023 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

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