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Question 40

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.
Assertion A:        

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 can be easily reduced using Zn $$-$$ Hg/HCl to

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.
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:

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Analysis of Assertion (A):

The reactant provided is a keto-alcohol (contains both a carbonyl group, $$\text{C=O}$$, and a hydroxyl group, $$\text{--OH}$$). When treated with Clemmensen reducing agent (amalgamated zinc and concentrated hydrochloric acid, $$\text{Zn--Hg/HCl}$$), two distinct chemical transformations happen simultaneously:

  1. Reduction of the Carbonyl Group: The ketone group ($$\text{C=O}$$) is successfully reduced to a methylene group ($$\text{--CH}_2\text{--}$$).
  2. Substitution of the Hydroxyl Group: Because the reaction happens under highly acidic conditions using concentrated $$\text{HCl}$$, the secondary alcohol ($$\text{--OH}$$) undergoes a nucleophilic substitution reaction where it is replaced by a chlorine atom ($$\text{--Cl}$$).

Since the final product doesn't accurately shows the carbonyl converted to a alkane linkage and the hydroxyl replaced by chlorine, Assertion A is FALSE.


Analysis of Reason (R):

Reason (R) states that $$\text{Zn--Hg/HCl}$$ is standardly employed to reduce a carbonyl group down to a active methylene ($$\text{--CH}_2\text{--}$$) group. This is the fundamental definition of a Clemmensen reduction, making Reason R perfectly TRUE as an independent chemical statement.

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