Use resonance forms of the conjugate bases to explain why methanesulfonic acid (CH₃SO₃H,pK_a= -2.6) is a much stronger acid than acetic acid (CH₃COOH,pK_a =4.8)

Resonance structures constitute structures that explain the electron delocalization in a particular molecule. A molecule comprising several resonance structures possesses significant stability.

Numerous factors impact the acidic strength, and some of them include resonance and inductive effect. The conjugate base stability is more significant for a molecule comprising resonance effect, and such molecules are acidic.

The acidic strength decides the stability of a conjugate base. The acid comprising a more stable conjugate base is highly stable.

The methanesulfonate ion is stabilized by resonance and induction. It has three resonance structures. The sulfur atom is more electronegative than carbon and comprises a small role in stabilizing the negative charge on carbon.

The acetate ion has two resonance structures. It does not have an inductive effect to stabilize the anion. The resonance structures of acetate ion and methylsulfonate ion can be given as:

Resonance structures of acetate and methylsulfonate ion

Acetic acid is a mild acid, but methanesulfonic acid is stronger than acetic acid.