Dimroth–Reichardt ET parameter

A measure of the @I03215@ (loosely @P04710@) of a solvent, based on the maximum wavenumber of the longest @W06659@ electronic absorption band of:
in a given solvent. \(E_{\text{T}}\), called \(E_{\text{T}}(30)\) by its originators, is given by: \[E_{\text{T}} = 2.859\times 10^{-3}\ \nu = 2.859\times 10^{4}\ \lambda ^{-1}\] where \(E_{\text{T}}\) is in \(\text{kcal mol}^{-1}\), \(\nu \) is in \(\text{cm}^{-1}\) and \(\lambda \) is in \(\text{nm}\). The so-called normalized \(E_{\text{T}}^{\text{N}}\) scale is defined as: \[E_{\text{T}}^{\text{N}}=\frac{E_{\text{T}}\left(\text{solvent}\right)- E_{\text{T}}\left(\text{Si}\text{Me}_{4}\right)}{E_{\text{T}}\left(\text{water}\right)- E_{\text{T}}\left(\text{Si}\text{Me}_{4}\right)}=\frac{E_{\text{T}}\left(\text{solvent}\right)- 30.7}{32.4}\]
See also:
Grunwald–Winstein equation
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1106 [Terms] [Paper]