A ketone, in the presence of a strong base like LDA, loses an acidic α hydrogen to give an enolate ion, which is stabilized by resonance. Its hybrid structure reveals negative charges on the carbonyl oxygen and the α carbon. The ambident enolate nucleophile can attack an electrophile via two potential reactive sites: the anionic oxygen or the anionic α carbon. Reactions through O-attack are less preferred than C-attack. This is because the oxygen site is less accessible, as the positive counterpart of the base stays more strongly attached to the oxygen than to the α carbon. Moreover, in the O-attack product, the strong carbonyl bond is lost, which is otherwise retained in the C-attack product. In summary, to alkylate a ketone, the ketone is first reacted with a strong base to give an enolate, which undergoes a C-attack with an alkyl halide in an SN2 reaction to produce an α-alkylated ketone.