1.

Dissociation constant of benzoic acid, p-nitro benzoic acid and p-hydroxy benzoic acid are 6.3 xx 10^(-5), 36 xx 10^(-5) " and ", 2.5 xx 10^(-5) respectively. Explain

Answer»

Solution :
(i) `NO_(2)` group is an electron withdrawing group and tends to stabilise the carboxylate anion more than the benzoate ion after the RELEASE of `H^(+)` ion. Thus, `p-`nitrobenzoic acid is a stronger acid than benzoic acid.
(ii) OH group is an electron releasing group and tends to DESTABILISE the carboxylate anion more than the benzoate ion after the release of `H^(+)`ion. Thus, `p-`hydroxybenzoic acid is a WEAKER acid than benzoic acid.
The relative order of acidic STRENGTHS is, thus, justified


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