Chemistry
Chemistry
Problem
When benzoic acid (C₆H₅COOH) and p-aminobenzoic acid (H₂NC₆H₄COOH) are dissolved separately in dimethyl sulfoxide (DMSO), which one is expected to be the stronger acid? Justify your choice in one to two sentences.Intuitive explanation
Benzoic acid is the stronger acid because p-aminobenzoic acid has an electron-donating amino group () directly attached to the benzene ring, which increases electron density at the carboxyl group and stabilizes the conjugate base less effectively than benzoic acid's unsubstituted ring. The amino group's resonance donation destabilizes the negative charge on the carboxylate ion, making deprotonation less favorable.
Intuitive explanation
Benzoic acid is the stronger acid because p-aminobenzoic acid has an electron-donating amino group () directly attached to the benzene ring, which increases electron density at the carboxyl group and stabilizes the conjugate base less effectively than benzoic acid's unsubstituted ring. The amino group's resonance donation destabilizes the negative charge on the carboxylate ion, making deprotonation less favorable.