Question

Reaction by which Benzaldehyde cannot be prepared?

A.

 

B.

C.

D.

Answer 1

Hint:. Substances like $Zn$ and conc $HCl$ are accustomed to convert the chemical group or, aldehyde or ketone group to methylene radical.

Complete step by step answer:
Before starting with the question, allow us to get to grasp some important reactions in chemical science.
Etard Reaction: The Etard reaction is an organic chemical action which involves the direct oxidation of an heterocyclic or aromatic bound methyl to an aldehyde using chromyl chloride, or As an example, the compound toluene may be easily oxidized to benzaldehyde.

Rosenmund Reaction: The Rosenmund reduction may be a process of hydrogenation during which an acyl chloride is selectively reduced to an aldehyde. The rosenmund reaction is catalyzed by reagents like palladium or barium sulphate..

Gatterman Koch Reaction: The Gattermann Koch reaction, may be a reaction within which aromatic compounds are reacted by a combination of chemical compound and acid within the presence of a catalyst, preferable is a Lewis acid, like $AlC{{l}_{3}}$.

Now, allow us to come to our answer options. watching option A, we are able to determine that the reaction occurring is Etard reaction and it can form benzaldehyde as a product.
Option B is none aside from Rosenmund reaction and it reduces the radical and forma benzaldehyde
In option C, the reaction occurring is Gatterman Koch and even it gives benzaldehyde as the final major product.
It is only in option D, where benzaldehyde can not be formed.
So, the correct answer is “Option D”.

Note: In Rosenmund reaction, the role of sulphate is that it reduces the activity of palladium because of its low expanse meaning that it decreases the reducing power of palladium so as to forestall excess reduction of the acid.