Question

Identify the reagent 'R' used in the following reaction
\(\text{C}_6\text{H}_5\text{COCl}\overset{\text{R}\,}{\rightarrow }\text{C}_6\text{H}_5\text{CHO}+\text{HCl}\)

• A. \(\text{CO},\text{HCl}\)
• B. \(\text{H}_2,\text{Pd}-\text{BaSO}_4\)
• C. \(\text{DIBAl}-\text{H}\)
• D. \(\text{H}_2\text{O}\)

Hint:

Rosenmund reduction uses H2 over poisoned palladium.

Answer 1

The Correct Option is B

Step 1: Match the by-product:
The equation shows HCl as the by-product, which is the Rosenmund pattern: the Cl of the acid chloride is replaced by H from hydrogen.

Step 2: Eliminate:
CO/HCl (Gattermann-Koch) formylates arenes and does not act on an acid chloride. $\text{H}_2\text{O}$ gives benzoic acid and HCl, not benzaldehyde.

Final Answer:
The reagent is $\text{H}_2$, $\text{Pd-BaSO}_4$, option (B). \[ \boxed{\text{H}_2,\ \text{Pd-BaSO}_4} \]