Zucker–Hammett hypothesis

https://doi.org/10.1351/goldbook.Z06751
This hypothesis states that, if in an acid catalysed reaction, $$\log _{10}k_{1}$$ (first-order @O04322@ of the reaction) is linear in $$H_{0}$$ (Hammett @A00081@), water is not involved in the @T06468@ of the @R05139@. However, if $$\log _{10}k_{1}$$ is linear in $$\log _{10}\left[\text{H}^{+}\right]$$ then water is involved. This has been shown to be incorrect by Hammett himself.
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1176 [Terms] [Paper]