Carbonyl derivatives with a proton on an a-carbon react with a suitable base to generate a carbon nucleophile called an enolate anion. Enolate anions react as a nucleophile in acyl addition, acyl substitution and alkylation reactions. A powerful base such as an organolithium is required to remove the proton from nitrogen. An acid-base reaction is an equilibrium. The nature of the base plays a major role in the position of the equilibrium after deprotonation of an aldehyde or ketone. An aldol condensation with different ketones can lead to very interesting aldol products. The ability to control the equilibrium of an aldol condensation reaction was accomplished when non-nucleophilic bases were developed.