Onsager-Kirkwood parameter

Figure 10 Solvation free energy versus the Onsager-Kirkwood parameter (e — l)/(2e + 1).

The importance of light absorption to directly populate the triplet state in the presence of heavy atoms [(10.271)] and the effect of heavy atoms on the phosphorescence of acenaphthylene [(10.27m)] are easily ruled out. No new absorption bands or increased band intensities are noted in the presence of heavy atoms. Since no phosphorescence is observed, even at low temperature, there cannot be an important effect on this process. A heavy-atom effect on the partitioning of reactions (10.27g,h) and (10.27k) is eliminated by the data of Hartmann, Hartmann, and Schenck in their study of solvent effects on the photosensitized photolysis of acenaphthylene. The influence of a number of solvents was described with the use of Kirkwood-Onsager solvent parameters (an empirical method for the correlation of reaction rate with the ability of the solvent to stabilize the change in dipole moment in proceeding to the transition state). A linear plot of log(fra/u/cw) vs. the expression [(Z) — 1)/(2Z) -f- where D is the dielectric constant, p is... 

It may be of some concern that the solvent dielectric properties are nowhere in evidence in this correlation, but that is the result of the solvents chosen. All have a value of the Kirkwood-Onsager (KO) parameter between 0.44 and 0.48. Only if data in solvents of very low dielectric constant are included (e.g. benzene, ether, THF, ethyl acetate) is there a contribution from the KO function [44] ... 

We conclude this section by discussing an expression for the excess chemical potential in temrs of the pair correlation fimction and a parameter X, which couples the interactions of one particle with the rest. The idea of a coupling parameter was mtrodiiced by Onsager [20] and Kirkwood [Hj. The choice of X depends on the system considered. In an electrolyte solution it could be the charge, but in general it is some variable that characterizes the pair potential. The potential energy of the system... 

Ab initio SCRF/MO methods have been applied to the hydrolysis and methanol-ysis of methanesulfonyl chloride (334). ° The aminolysis by aromatic amines of sulfonyl and acyl chlorides has been examined in terms of solvent parameters, the former being the more solvent-dependent process.Solvent effects on the reactions of dansyl chloride (335) with substituted pyridines in MeOH-MeCN were studied using two parameters of Taft s solvatochromatic correlation and four parameters of the Kirkwood-Onsager, Parker, Marcus and Hildebrand equations. MeCN solvent molecules accelerate charge separation of the reactants and stabilize the transition... 

For such a comparison one has to consider the step of the density at the phase transition. All the other relations which connect molecular parameters such as the molecular dipole moment /i, the polarizability a and the angle between the molecular long axis and fj, with each other have a general problem the calculation of the internal field and its anisotropy. Therefore, all the equations given in Vol. 1, Chap. VII.2 are necessary and useful but one has to take always into account the limitations of the models. Nevertheless, the Onsager theory [27] (basis for the Maier-Meier model [28]) and Kirkwood-Frbhlich model [29] have been... 

In relation to general interactions, the solvent is assumed to be a dielectric continuum. The earliest models for this type of interaction were developed by Kirkwood and Onsager, and were later modified with corrections for the effect of electrostatic saturation. " The intrinsic difficulty of these models in accurately determining the dimensions of the cybotactic region (viz. the solvent region where solvent molecules are directly per-tmbed by the presence of solute molecule) that surrounds each solute molecule in the solvent bulk, have usually raised a need for empirical approximations to the determination of a parameter encompassing solvent polarity and polarizability. An alternative approach to... 

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