Chapter 3, Problem 40P

Malonic acid, ${\text{HO}}_{\text{2}}{\text{CCH}}_{\text{2}}{\text{CO}}_{\text{2}}\text{H}$, is a diprotic acid. The $\text{p}{K}_{\text{a}}$ for the loss of the first proton is 2.83; the $\text{p}{K}_{\text{a}}$ for the loss of the second proton is 5.69. (a) Explain why malonic acid is a stronger acid than acetic acid ( $\text{p}{K}_{\text{a}}=4.75$). (b) Explain why the anion, ${}^{-}{\text{O}}_{\text{2}}{\text{CCH}}_{\text{2}}{\text{CO}}_{\text{2}}\text{H}$, is so much less acidic than malonic acid itself.