General multiparameter correlation analysis of solvent effects

1 General multiparameter correlation analysis of solvent effects 

Multiparameter correlation analyses of the effect of solvent on rates and equilibria were introduced by Koppel and Palm [37], but these have been utilized extensively by Taft and his students who recognized the contribution of five factors [38]. These are (i) the abihty of the solvent to stabilize an ion or dipole by dielectric effects (n ) (ii) the polarizability of the solvent (iii) the hydrogen-bond donation (a) (iv) the acceptor ability (P) and (v) the cohesive energy density of the solvent (8 ). In the case of the solvolysis reaction of t-butyl chloride, Taft s group found that the logarithm of the rate constant in 21 solvents from water to diethyl ether could be correlated with four factors [39]  

However, when the free energies of transfer of t-butyl chloride in these same solvents were determined, the data provided a good correlation with the same four factors but only the cohesive energy density term was significant [33]  

When the free energies of transfer of the ground state were subtracted from the free energies of activation, the free energies of transfer of the transition state were obtained, and these correlated well with the same four factors  

However, the dominant factors affecting the transition state are the ability of the solvent to stabilize dipoles and the ability of the solvent to donate a hydrogen bond. 

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See also in sourсe #XX -- [ ]

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