Q20 / 155 · WBJEE 2017 · Chemistry
The correct order of acid strengths of benzoic acid $(X),$ peroxybenzoic acid $(Y)$ and $p$-nitrobenzoic acid $(Z)$ is
- A$Y>Z>X$
- B$Z>Y>X$
- Correct answerC$Z>X>Y$
- D$Y>X>Z$
Solution
$\because$ In $p$ -nitrobenzoic acid $(Z)-\mathrm{NO}_{2}$ present as electron withdrawing group, thus is most acidic
$(X) \because$ Benzoic acid is stabilised via resonance, thus is more acidic than per oxybenzoic acid.
(Y) peroxy benzoic acid does not show any such resonance.
Thus is least acidic.
Hence, correct order is $Z>X>Y$
$(X) \because$ Benzoic acid is stabilised via resonance, thus is more acidic than per oxybenzoic acid.
(Y) peroxy benzoic acid does not show any such resonance.
Thus is least acidic.
Hence, correct order is $Z>X>Y$Hence, the correct answer is option: 'C'.