Dimroth-Reichardt parameter

Physical organic chemists have tended to examine parameters based on shifts in the absorption peaks in the spectra of various dyes or indicator molecules. The a and P scales of Taft and Kamlet, the ET(30) scale of Dimroth and Reichardt, the 7t scale of Taft and co-workers and the Z value of Kosower are all examples of this type of parameter. The definitions and measurement means for these parameters, as well as important references, are shown in Table 5. An alternative definition of the Dimroth-Reichardt parameter is the dimensionless, ETN, which is now preferred by some organic chemists (for a discussion see Ref. 15). The Z value is important in that it led to the scale of Dimroth and Reichardt, which overcomes many of the limitations of the earlier scale. Several workers have shown that relationships exist, with good correlation coefficients, between similar parameters. Thus, DN is linearly related to p, both parameters being designed to measure the donor properties (or Lewis basicity) of solvent molecules. Also, Lr(30) is related to a as well as to AN all three parameters purport to measure the electron acceptor properties (or Lewis acidity) of solvent molecules. It has been found that different solvent types have different coefficients in linear relationships between n and the dipole moment. The Taft and Dimroth-Reichardt parameters, in particular, have been found to correlate with free energies and... 

Solvatochromic effects occur then the color of a solute depends on the nature of the solvent in which it is dissolved. Two such systems were discussed in section 4.9. The first is the betaine dye, 4-(2,4,6-triphenylpyridinium)-2,6-diphenylphen-oxide, which is used to define the Dimroth-Reichardt parameter Ej. This molecule undergoes a ti ti transition in the visible region whose wavelength is very solvent dependent. In the strongly acidic solvent water it is equal to 453 nm which corresponds to an energy gap of 264kJmoH. In the very weakly acidic solvent diphenylether, the wavelength for the same transition is 810 nm. This corresponds... 

It is generally well understood that values of E1/2 can vary markedly as a function of solvent. Numerous papers have been published in this area and they often include correlations between E1/2 and one or more solvent parameters such as the Gutmann donor number, the Gutmann acceptor number, or the Dimroth-Reichardt parameter [14]. In general, values of E1/2 have been shown to correlate with the Gutmann donor number for electrode reactions of the type where n is a... 

Figure 7.5. Correlation of half-wave potentials for the first three electron transfers of Ceo and (a) the Guttmann donor number and (b) normalized Dimroth-Reichardt parameter ( -r (30)) of the solvent in solutions containing 0,1 M TBACIO4. See text in Table 7.1. for abbreviations. (Reprinted with permission from ref 34. Copyright 1992, American Chemical Society.)...

The correlation between the Dimroth-Reichardt ET(30) and the Kosower Z solvent polarity parameters, Eq. (4.8), both in kcal mol 1... 

Oxygenation of 2-substituted adamantanes with methyl(trifluoromethyl)dioxirane showed a reaction constant, p = -2.31, consistent with a strongly electron-demanding transition state. Analysis of the effect of solvents on the rate yielded a positive regression coefficient with Dimroth-Reichardt Ej solvent polarity parameter. A mechanism involving an electrophilic O atom insertion has been postulated for the formation of alcohols and carbonyl compounds.201... 

Dimroth-Reichardt ET parameter A measure of the IONIZING POWER (loosely polarity) of a solvent, based on the maximum wave number of the longest wavelength electronic absorption band of... 

See also Dimroth-Reichardt et parameter Grunwald-Winstein equation. 

Descriptor 6, is the Reichardt-Dimroth (30) parameter[24] expressed in SI units. (30) defined as the transition energy (kcal) at 25 C of the long wave absorption band of standard betain dyes when dissolved in the solvent. Descriptor 8, log P is the logarithm of the equihbrium constant of the distribution of the solvent between 1-octanol and water at 25 °C. 

The Kosower parameter (Z = //v) is derived from the effect of the solvent on the charge transfer spectrum of the pyridinium iodide (5) excitation. A high value of Z (the energy of the charge transfer transition) corresponds to highly polar solvents. Similar parameters have been obtained for other reporter molecules and the charge transfer system of 6 generates the Dimroth-Reichardt scale. 

C, Pc = 73.83 bar, = 0.467 g mL , ought to be utilized. [5] In terms of polarity, SC-CO2 [Dimroth-Reichardt t(30) value of 32 [6]] is roughly comparable to carbon tetrachloride. However, differences remain when the Kamlet-Taft n solvatochromicity parameter n = -0.2) [7] is taken into account. Thus, SC-CO2 could be used as a replacement for commonly used organic solvents. Until 1994 it appears that most experiments have been primarily governed by academic curiosity, however, interest has largely increased since. 

Dimroth-Reichardt t(30) solvatochromic polarity parameter in kJ/mol taken from [145]. 

Dimroth-Reichardt solvatochromic polarity parameter t(30) converted to kJ/mol units... 

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