Question

From which of the following compounds can HO^- remove a proton in a reaction that favors product formation?

Short answer

The removal of protons for reaction 3 is the most stable one as it produces carboxylate ion which further undergoes resonance stabilization and produces 2 canonical structures.

Step-by-step solution

Hydrogen Abstraction

Among the 4 compounds, that compound will favor the H⁺ abstraction reaction which will be stabilized after that. The reaction with OH^- with all the compounds are given below,

Explanation For The Favoured Reaction

Here, reaction 1 will be the most favourable product formation.

$C{H}_{3}CO{O}^{-}$ is an anion with a resonance stabilization. Due to the -I effect of the ketone group, the electron density on O will decrease and there will be an electron delocalisation as well as increases its stability.

The product formed in reaction 3 is$C{H}_{3}C{H}_{2}N{H}_2$which has fulfilled octet. But the stability of primary amine is not that much of secondary, tertiary amine or carboxylate ion as it will have only one $-C{H}_3$group to increase its electron density.

Reaction 2 and 4 both are unstable as there is no such resonance stability or no group having -I effect to decrease the electron density.

So, formation of carboxylate ions is the most stable one.