Chemistry - GOC Question with Solution | TestHub

Removing ${\mathrm{H}}_1$ gives a carbanion between the two carbonyls :

Removing ${\mathrm{H}}_2$ gives the carboxylate :

The carboxylate carries the negative charge on oxygen, delocalised over two oxygens by resonance; the carbanion carries it largely on carbon ($\mathrm{p}{K}_{\mathrm{a}}$ of the α C-H here ~ 11, of the acid O-H ~ 3). The carboxylate is far more stable, so the O-H proton ${\mathrm{H}}_2$ is much more acidic.