Relationship between nucleophilicity/electrophilicity indices and reaction mechanisms for the nucleophilic substitution reactions of carbonyl compounds

Theoretical electrophilicity and nucleophilicity scales, defined in terms of electronic reactivity indices, were tested for the reaction of a series of carbonates with neutral and charged reagents of varying nucleophilicity. The electrophilicity and nucleophilicity scales were used to rationalize some mechanistic aspects developed by these reacting systems: the greater the electrophilicity/nucleophilicity difference, the more concerted the reaction mechanism will be. Conversely, a small electrophilicity/nucleophilicty gap will in general be associated with a stepwise reaction mechanism.