Cross-interaction constants as a measure of the transition-state structure. Part 4. Brønsted-type cross-interaction constants

Abstract

The Brønsted-type (β_ij) and the mixed Hammett-Brønsted type (λ_ij) cross-interaction constants are introduced, and inter-relationships between various parameters are deduced in order to provide some quantitative basis for the two parameters. The β_ij value represents a more direct measure of the transition-state structure and has the advantage of wider applicability over the Hammett-type constant (ρ_ij), which contains two constant factors corresponding to the interactions between substituents and reaction centres. The λ_ij values are found to be useful as a measure of the transition-state structure for a reaction series in which only one fragment involves a substituent change.