Question

Compare the two methods shown for the preparation of carboxylic acids :
Method 1 :$RBr\underset{diethyleither}{\overset{Mg}{\to }}RMgBr\underset{2.H_3{O}^{+}}{\overset{1.C{O}_2}{\to }}RC{O}_{2}H$
Method 2 : $RBr\stackrel{NaCN}{\to }RCN\underset{heat}{\overset{H_{2}O,HCl}{\to }}RC{O}_{2}H$
Which one of the following statements correctly describes this conversion ?

• A. Both method 1 and method 2 are appropriate for carrying out this conversion
• B. Neither method 1 nor method 2 is appropriate for carrying out this conversion
• C. Method 1 will work well, but method 2 is not appropriate
• D. Method 2 will work well, but method 1 is not appropriate

Answer 1

Answer: (C)

Method 1 will work well, but method 2 is not appropriate

This method is the best one.But method $-2$ is not appropriate as the first step is a $S{N}^2$ displacement which does not takes due to stearic hindrance.