Grunwald–Winstein equation

The linear free energy relation:

$log 10 ( k s k 0 ) = m Y$

expressing the dependence of the rate of solvolysis of a substrate on ionizing power of the solvent. The rate constant $k 0$ applies to the reference solvent (ethanol–water, 80:20, v/v) and $k s$ to the solvent s, both at $25 °C$ . 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 solvents. The equation was later extended to the form:

$log 10 ( k s k 0 ) = m Y + l N$

where $N$ is the nucleophilicity of the solvent and $l$ its susceptibility parameter. The equation has also been applied to reactions other than solvolysis.

Source:

PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1118