The linear free energy relationlog(ks/k0) = mYexpressing the dependence of the rate of solvolysis of a substrate on ionizing power of the solvent. The rate constant k0 applies to the reference solvent (ethanol-water, 80:20, v/v) and ks to the solvent s, both at 25 oC. The parameter m is characteristic of the substrate and is assigned the value unity for tert-butyl chloride. The value Y is intended to be a quantitative measure of the ionizing power of the solvent s. The equation was later extended by WINSTEIN, GRUNWALD and JONES (1951) to the form
log(ks/k0) = mY + lNwhere N is the nucleophilicity of the solvent and l its susceptibility parameter. The equation has also been applied to reactions other than solvolysis. [For the definition of other Y-scales, see BENTLEY and SCHLEYER (1977), BENTLEY and LLEWELLYN (1990).] GRUNWALD and WINSTEIN (1948); FAINBERG and WINSTEIN (1956). See also Dimroth-Reichardt ET parameter, polarity, Z-value.
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