The acetyl group (-COCH3) in o-acetylbenzoic acid is an electron-withdrawing group. It withdraws electrons from the benzene ring, which makes the hydrogen atom on the carboxylic acid group more acidic. This means that o-acetylbenzoic acid will more readily lose its hydrogen ion (H+), resulting in a lower pH.

In contrast, benzoic acid does not have any electron-withdrawing groups on the benzene ring. This means that the hydrogen atom on the carboxylic acid group is less acidic, and benzoic acid will not lose its hydrogen ion as easily as o-acetylbenzoic acid. As a result, benzoic acid will have a higher pH.

The difference in acidity between benzoic acid and o-acetylbenzoic acid can be seen in their pKa values. The pKa of benzoic acid is 4.20, while the pKa of o-acetylbenzoic acid is 3.45. The lower pKa value of o-acetylbenzoic acid indicates that it is more acidic than benzoic acid.