CHARGE-TRANSFER TRANSITION ENERGIES AND THE PREDICTION OF REACTIVITY IN ELECTROPHILE NUCLEOPHILE REACTIONS

The differences between charge-transfer transition energies calculated for donor-acceptor pairs at infinite separation and values determined experimentally for the charge-transfer complex geometry vary according to the charge type of the pairs and within a group of fixed charge type. It is argued that these differences provide a guide to the slope of the state-correlation curves for the product configuration in electrophile-nucleophile reactions of the corresponding charge type and that the observed variation invalidates the use of the simple expression DELTA-E = f-GAMMA - beta with constant f, derived from the curve-crossing model, to estimate energy barriers to reaction.