Which of the following aromatic acids is most acidic?

Options

A.
B.
C.
D.

Answer

B

Explanation

It is due to ortho-effect i.e., ortho substituted acid is stronger. Benzoic acid is a resonance hybrid, and so the carbonyl group is coplanar with the ring. An osubstituent tends to prevent this coplanarity. The resonance is diminished (or prevented), and so the O atom of the – OH group has a greater positive charge, resulting in increased acid-strength.