Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylicacid is a stronger acid than phenol. Why

The acidity of a compound is determined by the stability of its conjugate base. A more stable conjugate base makes the compound a stronger acid.

1. Phenol and carboxylic acid both lose a proton (H+) to form their respective conjugate bases, phenoxide ion and carboxylate ion.

2. Although phenoxide ion has more resonating structures than carboxylate ion, the negative charge in the carboxylate ion is not only delocalized over two oxygen atoms but also over the more electronegative oxygen atoms. This makes the carboxylate ion more stable than the phenoxide ion.

3. In addition, the carboxylate ion has an extra oxygen atom which can accommodate the negative charge more effectively due to its higher electronegativity. This further stabilizes the carboxylate ion.

4. Therefore, despite having fewer resonating structures, the carboxylate ion is more stable than the phenoxide ion. This makes carboxylic acid a stronger acid than phenol.