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Solvent Effects on ρ Values of the Hammett Equation

1969; Oxford University Press; Volume: 42; Issue: 4 Linguagem: Inglês

10.1246/bcsj.42.1037

1348-0634

Yasuhiko Kondo, Takeki Matsui, Niichiro Tokura,

Spectroscopy and Quantum Chemical Studies

Abstract The effects of selvents on ρ values have been systematically treated as a two-variable problem within a linear free-energy relationship framework. It is assumed that the standard activation free energy is a continuous function of σ, a substituent variable, and ξ, a solvent variable. The applicability of the resultant equations is proved by a test of the dissociation constants (obtained from the literature) of benzoic acids in various solvents. As a result, it is proposed that these effects on ρ values can be explained in terms of the interaction or cross-term of σ and ξ. The application to the reaction rates of a typical Menschutkin reaction, obtained by experiments in ten nonaqueous solvents, suggests that the solvent dependence in these reactivities is much more complicated.