Question

$H_{3}C-COCl\underset{}{\overset{H_2/Pd-BaS{O}_4}{\to }}A\underset{}{\overset{Zn-Hg/HCl}{\to }}B$
What are A and B?

• A. $H_{3}C-C{H}_{2}Cl,H_{3}C-C{H}_3$
• B. $H_{3}C-CHO,H_{3}C-C{H}_3$
• C. $H_{3}C-C{O}_{2}H,H_{3}C-C{H}_3$
• D. $H_{3}C-C{H}_{2}OH,H_{3}C-C{H}_3$

Answer 1

Answer: (B)

$H_{3}C-CHO,H_{3}C-C{H}_3$

$H_{3}C-COCl\underset{}{\overset{H_2/Pd-BaS{O}_4}{\to }}C{H}_3-CHO\underset{}{\overset{Zn-Hg/HCl}{\to }}C{H}_3-C{H}_3$
1. Rossenmund reduction : in first step
The catalytic hydrogenation of acid chlorides allows the formation of aldehydes

2. Clemmensen reduction : in 2nd step
accomplishes the same using amalgamated zinc, Zn(Hg), and concentrated HCl. Used when starting materials are sensitive to base.
>$C=O\underset{HCl,Heat}{\overset{Zn\left(Hg\right)}{\to }}>C{H}_2$