Question

Which one of the following is reduced with $Zn/Hg$ and hydrochloric acid to give the corresponding hydrocarbon?
(A) Ethyl acetate
(B) Acetic acid
(C) Acetamide
(D) Butan-2-0ne

Answer 1

Hint: Clemmensen reduction is a reaction of aldehydes and ketones with zinc amalgam (Zn/HG) in presence of concentrated hydrochloric acid, which further reduces the aldehyde or ketone to a hydrocarbon. Zinc amalgam is most commonly used in this reaction.

Complete step by step answer:
The clemmensen reduction is a reaction that is used to reduce aldehydes or ketones to alkanes using hydrochloric acid and zinc amalgam. This reduction is named after a Danish chemist, Erik Christian Clemmensen.
Now, among the given options Butan-2- 0ne reduces with $Zn/Hg$ and hydrochloric acid to give the corresponding hydrocarbon because it is a ketone. The reduction takes place at the surface of the zinc catalyst.
The reaction is as shown:
$C{H_3}C{H_2}COC{H_3} + 4[H]\xrightarrow{{Zn/Hg\,and\,HCl}}C{H_3}C{H_2}C{H_3} + {H_2}O$
This reaction is particularly effective in aryl-alkyl ketones reduction formed in Friedel-crafts acylation. The reaction is further more effective in reduction of cyclic ketones or aliphatic and zinc metals.

Hence, option D is correct.

Note: In this reaction, alcohols are not postulated as intermediates because the subjection of the corresponding alcohols to these same reaction conditions does not further lead to alkanes. There are further two mechanisms involved in the reduction i.e. caranionic mechanism and carbenoid mechanism.