While acyl chlorides react at an enolate's oxygen site to yield enol esters, alkyl halides usually react via the α carbon. This is because an enolate is an ambident nucleophile. Its nucleophilic oxygen and a carbon can both attack an electrophile, called O-attack and C-attack, respectively. Although the enolate's oxygen atom bears most of the negative charge, most reactions involve a C-attack rather than an O-attack because the α carbon has a greater share of the HOMO. While drawing the mechanism for the C-attack of an enolate, the realistic convention starts with the negative charge on oxygen, as the oxyanion is the more significant contributing structure. The simpler convention is to draw the C-attack with the negative charge on the α carbon. The carbanion is the less significant contributing structure, but fewer curved arrows are needed to depict the mechanism. The two conventions represent the same overall electron movement, so the choice is based on a preference for accuracy or simplicity.