溶媒極性綜報

Abstract

This paper contains recent reports of the solvent effect on reaction rate. As a measure of solvent polarity, for example, dielectric constant e and dipole moment μ, have been of wide use in organic chemistry. These parameters, however, are not appropriate for organic reactions from the theoretical point of view; which is ascertained in many exeriments. Accordingly, a kinetic measure of this effect, the Y - values of Winstein, are introduced with success by means of the solvolysis rate of alkyl halides. The usage of them is restricted for fact that these reactions cannot be carried out in a variety of solvents. A new independent parameter is proposed by Kosower on the spectroscopic method; which is based on the transition energy derived from the band position of the charge-transfer absorption of 1-alkyl-4-carbomethoxy pyridinium iodide complex. It is indicated that there is a linear correlation between the Kosower's Z and the Winstein's Y values. The meaning and application of them are explained in some detail theoretically. Other solvent parameters, such as Ω, S, E and δ, are all correlated with both Y and Z values. Then, these indices of the solvent palarity should be utilized for the organic reaction in solution, especially giving the deep insight to reaction mechanism and interaction between solute and solvent molecules.