Question

Which of the following reaction represents Rosenmund reduction ?

• A. \(\text{R}-\text{CO}-\text{Cl}\rightarrow _{\text{Pd}-\text{BaSO}_4\,}^{\text{H}_2\,}\text{R}-\text{CHO}+\text{HCl}\)
• B. \(\text{R}-\text{CN}\rightarrow _{\text{H}_3\text{O}^+\,}^{\text{SnCl}_2,\text{HCl}\,}\text{R}-\text{CHO}+\text{NH}_4\text{Cl}\)
• C. \(\text{R}-\text{CHO}\rightarrow _{\Delta \,}^{\text{Zn}-\text{Hg conc.HCl}\,}\text{R}-\text{CH}_3+\text{H}_2\text{O}\)
• D. \(\text{R}-\text{CO}-\text{R}\rightarrow _{\text{ii) KOH, HO}-\text{CH}_2-\text{CH}_2-\text{OH}, \Delta \,}^{\text{i) H}_2\text{N}-\text{NH}_2\,}\text{R}-\text{CH}_2-\text{R}\)

Hint:

Rosenmund reduction converts an acyl chloride to an aldehyde using H2 over poisoned Pd-BaSO4.

Answer 1

The Correct Option is A

Step 1: Name each reaction:
(A) acid chloride plus $\text{H}_2$ over Pd-BaSO4: Rosenmund. (B) nitrile plus $\text{SnCl}_2$, HCl, then hydrolysis: Stephen. (C) carbonyl plus Zn-Hg and conc. HCl: Clemmensen. (D) hydrazine then KOH, glycol: Wolff-Kishner.

Step 2: Pick:
Only (A) starts from an acyl chloride and ends in an aldehyde with $\text{H}_2$ and Pd-BaSO4.

Final Answer:
Option (A) is the Rosenmund reduction. \[ \boxed{\text{(A)}} \]