Because the reactivity only comes about through keto-enol tautomerism, some students forget to consider reactions at the α carbon when presented with an aldehyde or ketone in an MCAT question. For example, the α carbon of an enolate can act as a nucleophile. It can be used to react by nucleophilic substitution with alkyl halides. If you aren't thinking about keto-enol tautomerism, you would have a difficult time making the connection to such a product in the array of multiple choice answers.