Carbonyl coordination chemistry from a new angle: a computational study of alpha-carbon acidity based on electrophile coordination geometry.

[reaction: see text] The dependence of acidity on Li+ coordination geometry to alpha-carbon acids is investigated by generating potential energy surfaces of Li+ complexation with acetaldehyde and its respective enolate. The global minimum for the enolate complex shows significant Li+-pi-system coordination to both oxygen and the alpha-carbon. The gas-phase acidity analysis reveals significantly more alpha-carbon coordination, which presumably enhances the lability of the cleaving proton in the transition state of deprotonation.