Proton resolvation process

The above presented dependencies of the composition of solvate shell on the mixed solvent composition as well as resolvation constants permit calculation of the solvate composition by varying solvent composition. The dependence of resolvation constants on the permittivity of the solvent is discussed in the example of the proton resolvation process. 

Table 9.7. The components of free energy (kJ moU) of proton resolvation process at 298.15K...

Solvation energy of complex by solvent A is small beeause eoordination vacancies of the proton are saturated to a considerable extent. Therefore the interaetion energy between A and B influences significantly the value of oAG. That is why, die mixed solvents (alcohol-water and alcohol-pyridine, for instance) are different because of the proton resolvation process. This can be explained in terms of higher energy of heteromoleeular association for the alcohol-water in comparison with alcohol pyridine. 

The concept of solvent effect on the proton resolvation process was confirmed by quantum chemical calculations. Above phenomena determine the dependence of resolvation constant on physical and chemical properties. 

Let us consider the changes in the system, when donor component is added to protic acid HA in solvent A. Anion solvation can be neglected, if both solvents have donor character. The interaction influences the proton resolvation process. 

Proton transfer processes are specially important excited state properties, and several detailed time resolved studies have been reported. Time resolved fluorescence studies of excited l-naphthol-3,6-disulphonate shows there is geminate recombination by proton transfer. Another detailed study is the examination of proton transfer and solvent polarization dynamics in 3-hydroxyflavone . The dynamics of proton transfer using a geminate dissociation and recombination model has also been investigated with 8-hydroxypyrene-l,3,6-trisulphonate 5 and also with... 

Several detailed time-resolved studies of proton transfer processes have been described this year see for example Masad and Huppert. 

Let the resolvation process proceeds at substantial abundance of the component A in mixed solvent and initial concentrations HA (HA" ) and B to be equal. The output of the process can be calculated from the equation similar to equation [9.66]. The large value of K s in all considered processes of proton resolvation indicates the effect of permittivity change on the yield of complex HB formation. The output of resolvated proton in process [9.104] proceeding in methanol equals 100%, whereas in the same process in low polarity solvent (e.g., methanol-hexane), with abundance of the second component, the equilibrium is shifted to the left, resulting in solvate output of less than 0.1%. K s values in single alcohol solvents are large, thus the output of reaction does not depend on solvent exchange. 

Solvation energy of proton by donor solvents is very high. The regularities of the proton selective solvation and resolvation processes were studied in more detail in comparison with other ions. 

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