Term: Grunwald–Winstein equation
https://doi.org/10.1351/goldbook.G02710

Definition:
The linear free energy relation: \[\log _{10}(\frac{k_{\text{s}}}{k_{0}}) = m\ Y\] expressing the dependence of the rate of solvolysis of a substrate on ionizing power of the solvent. The rate constant k0 applies to the reference solvent (ethanol–water, 80:20, v/v) and ks 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: \[\log _{10}(\frac{k_{\text{s}}}{k_{0}}) = m\ Y+l\ N\] where N is the nucleophilicity of the solvent and l its susceptibility parameter. The equation has also been applied to reactions other than solvolysis.

Related Terms:
1) dimroth–reichardt <em>e</em><sub>t</sub> parameter (http://doi.org/10.1351/goldbook.D01746).
2) polarity (http://doi.org/10.1351/goldbook.P04710).
3) <em>z</em>-value (http://doi.org/10.1351/goldbook.Z06737).
4) free energy (http://doi.org/10.1351/goldbook.F02515).
5) solvolysis (http://doi.org/10.1351/goldbook.S05762).
6) ionizing power (http://doi.org/10.1351/goldbook.I03215).
7) rate constant (http://doi.org/10.1351/goldbook.O04322).
8) nucleophilicity (http://doi.org/10.1351/goldbook.N04251).

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1118 (https://doi.org/10.1351/pac199466051077)

Citation: 'Grunwald–Winstein equation' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.G02710

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