Dimroth–Reichardt ET parameter

https://doi.org/10.1351/goldbook.D01746
A measure of the
ionizing power
(loosely
polarity
) of a solvent, based on the maximum wavenumber of the longest
wavelength
electronic absorption band of:
in a given solvent. ET, called ET(30) by its originators, is given by: ET=2.859×103 ν=2.859×104 λ1 where ET is in kcalmol1, ν is in cm1 and λ is in nm. The so-called normalized ETN scale is defined as: ETN=ET(solvent)ET(SiMe4)ET(water)ET(SiMe4)=ET(solvent)30.732.4
See also:
Grunwald–Winstein equation
,
Z-value
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1106 [Terms] [Paper]