Term: Bunnett–Olsen equations
https://doi.org/10.1351/goldbook.B00758

Definition:
The equations for the relation between log10([SH+]/[S]) + H0 and log10[H+] + H0 for base S in aqueous mineral acid solution, where H0 is Hammett's acidity function and log10[H+] + H0 represents the activity function log10(γS.γH+)/γ.SH+ for the nitroaniline reference bases to build H0. \[\log _{10}(\frac{[\text{SH}^{+}]}{[\text{S}]})- \log _{10}[\text{H}^{+}]=(\varPhi - 1)\ (\log _{10}\text{[H}^{+}\text{]}+\text{H}_{0})+pK_{\text{SH}^{+}}\] \[\log _{10}(\frac{[\text{SH}^{+}]}{[\text{S}]})+H_{0}=\varPhi \ (\log _{10}[\text{H}^{+}]+\text{H}_{0})+pK_{\text{SH}^{+}}\]

Related Terms:
1) cox–yates equation (http://doi.org/10.1351/goldbook.C01386).
2) acidity function (http://doi.org/10.1351/goldbook.A00081).

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1091 (https://doi.org/10.1351/pac199466051077)

Citation: 'Bunnett–Olsen equations' 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.B00758

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