Question

Decreasing order of acidic strength of the following hydroxy benzoic acid is:

• A. $o->p->m-$
• B. $o->m->p-$
• C. $p->o->m-$
• D. $m->0->p-$

Answer 1

The correct option is B $o->m->p-$

In the o-isomer, a strong hydrogen bridge can be formed between the phenolic $-OH$ & the carboxylate anion which stabilizes the carboxylate base & hence more acidic.

In the m-isomer, there is no resonance but only $-I$ effect of $-OH$ group.

In the p-isomer, $-I$ effect is more.

Therefore the order of decrease of acidic strength is

$o->m->p-$