Enthalpy and entropy contributions to solvent effects on adduct formation

Thermodynamic parameters for adducts of organometallic acids with tributylphosphine and triphenylphosphine oxide in various solvents have been determined by NMR and calorimetric analysis. These data combined with previously reported data on hydrogen-bonded and other adduct systems have been used to correlate and interpret solvent effects on the thermodynamics of adduct formation in organic media. Linear free energy (LFE) relationships are analyzed in terms of solvent effects on the enthalpy and entropy components of adduct formation. Empirical parameters related to electron pair donating and accepting abilities along with bulk solvent properties give LFE correlations which may be interpreted in terms of solute-solvent interactions