textbook 6c 21 b

[Ruiyu Li 3I]

The question is Suggest an explanation for the different strengths of acetic acid and formic acid. The answer is Formic acid is a slightly stronger acid than acetic acid. Can anyone help with this?

[Alex Yeghikian 1C]

I think the book was just stating which one was the stronger acid in the answers to account for the fact that there could be many explanations, but I agree that it's not very useful. Formic acid HCOOH differs from acetic acid CH₃COOH only in what is bonded to the carboxyl group. The hydrogen attached to the central carbon atom in formic acid will be more easily removed than the hydrogen attached to the oxygen atom in acetic acid, because the methyl group in acetic acid is contributing more electrons and thus adding to the polarization of the molecule and the strength of the O-H bond while the hydrogen in formic acid is not.