Question

For the following reaction:
$\text{Phenol}\underset{2.C{O}_2,H^{+}}{\overset{1.\text{Base}}{\to }}\text{Product(s)}$
Choose the correct option(s):

• A. o-salicylic acid will be the major product if the base is $NaOH$
• B. p-salicylic acid will be the major product if the base is $KOH$
• C. o-salicylic acid will always be the major product.
• D. p-salicylic acid will always be the major product.

Answer 1

Answer: (A), (B)

p-salicylic acid will be the major product if the base is $KOH$

Kolbe’s Reaction:

In the above reaction, o-salicylic acid is the major product when $NaOH$ is used as a base whereas p-salicylic acid is the major product when $KOH$ is used.
This is because a stabilized cyclic transition state is formed when $NaOH$ is used, whereas due to large size of $K$, it doesn’t fit into the cyclic transition state. Hence cyclic transition state cannot be formed and para isomer is the major product in case of $KOH$