Which among the following substituent groups decreases the acidic strength of aromatic carboxylic acid?
Which among the following substituent groups decreases the acidic strength of aromatic carboxylic acid?
$-\mathrm{NH}_{2}$
$-\mathrm{CN}$
$-\mathrm{Cl}$
$-\mathrm{N} \mathrm{O}_{2}$
Solution
$-\mathrm{NH}_{2}$ is electron donating group which activate the benzene ring to electrophilic attack and make aromatic carboxylic acids less acidic. While $-\mathrm{Cl},-\mathrm{CN}$ and $-\mathrm{NO}_{2}$ are electron withdrawing groups which increases the acidity of aromatic carboxylic acids.