6C 21 part b

[LBacker_2E]

Can someone give an explanation of why formic acid (HCOOH) is a stronger acid than acetic acid (CH3COOH) because the one in the textbook was a little confusing and unclear to me?

[KeyaV1C]

If the conjugate base is more stable, the compound it corresponds to is more acidic. If you look at the conjugate bases for formic acid and acetic acid, both conjugate bases are stabilized by resonance, and electronegativity. The main difference is that there's a CH3 group instead of an H adjacent to the carbonyl in the conjugate base of the acetic acid. This methyl group is an electron donating group which can destabilize the negative charge of the conjugate base which is why acetic acid is less acidic than formic acid.

[Wendy 1E]

Formic acid is stronger than acetic acid because acetic acid has a CH3 that is e- donating. This means that CH3 contributes electron density to the O-H bond. This makes it harder to remove the H. Thus it is weaker acid compared to formic acid.