JEE Advanced · 2011 · 10 Apr 2011 · Paper 1 · General Organic Chemistry

Among the following compounds, the most acidic is

(A) $p$ -nitrophenol
(B)p-hydroxybenzoic acid
(C) $o$ -hydroxybenzoic acid✓ Correct
(D) $p$ -toluic acid

Answer: (C)

Solution

o

-Hydroxybenzoic acid (salicylic acid) is the most acidic due to the ortho effect. The ortho-hydroxyl group forms an intramolecular hydrogen bond with the carboxyl group, stabilizing the carboxylate anion and making it easier to lose a proton.

The order of decreasing acidity is:

o

-hydroxybenzoic acid >

p

-hydroxybenzoic acid >

p

-nitrophenol >

p

-toluic acid

JEE Advanced · 2011 · 10 Apr 2011 · Paper 1 · Single correct option

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