Mayr–Patz equation

https://doi.org/10.1351/goldbook.08185
Rate constants for the reactions of spA2-hybridized electrophiles with nucleophiles can be expressed by the correlation lg⁡[k/(dm3mol−1s−1)]=sN(E+N) where E is the nucleophile-independent electrophilicity parameter, N is the electrophile-independent nucleophilicity parameter, and sN is the electrophile-independent nucleophile-specific susceptibility parameter.
Notes:
  1. This equation is equivalent to the conventional linear Gibbs energy relationship lg⁡k=Nu+sNE, where Nu=sNN. The use of N is preferred, because it provides an approximate ranking of relative reactivities of nucleophiles.
  2. The correlation should not be applied to reactions with bulky electrophiles, where steric effects cannot be neglected. Because of the way of parametrization, the correlation is applicable only if one or both reaction centers are carbon.
  3. As the E parameters of the reference electrophiles are defined as solvent-independent, all solvent effects are shifted into the parameters N and sN.
  4. The equation transforms into the Ritchie equation for sN=1.
  5. Applications to SN2-type reactions are possible if an electrophile-specific susceptibility parameter is introduced.
  6. The Mayr scale is available at https://www.cup.lmu.de/oc/mayr/DBintro.html.
Source:
PAC, 2022, 94, 353. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)) on page 460 [Terms] [Paper]
Citation: 'Mayr–Patz 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.08185 RIS BibTex EndNote
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