ADDITION OF NEW DONORS TO THE E AND C MODEL

The enthalpies of adduct formation of donors with BF3 measured in CH2Cl2 and the free energies of proton transfer from ammonia to nonprotonic, second-row donors in aqueous solution are found to correlate with the E and C equation. Conditions for fitting data, which are not solvation minimized, to the E and C model are described, and a complete analysis of the solution contribution to the BF3 enthalpies is presented. These new acceptor systems and a series of recently reported spectral probes lead to the addition of over 40 new donors to the E and C data base. The new parameters and a complete listing of the recommended transformed set of parameters are offered here for the first time, providing a complete data base of all known parameters for the E and C model. New donors are readily added to the correlation by using enthalpies and the probes described in this article. The extension of the E and C model to these new donors and acceptors facilitates its use as a scale of donor and acceptor strengths in the dual parameter analysis of physicochemical data.