Solvation, of proton

The cationic species—that is, solvation of proton by HF—has also been the subject of various theoretical approaches in association with the development of the superacid field. 

Due to the solvation of protons by hydrogen peroxide, an oxonium structure is observed, as in Equation (4.53) this structure changes the nature of the peroxide bond and thus increases its stability. 

An analysis of the transport properties of alkali metal halides in TFE led to association constants, which were interpreted in terms of greater anion solvation by TFE than by ethanol and also less cation solvation by TFE (19). Despite evidence that chloride ion is strongly solvated by TFE, HC1 is about 15 times more soluble in ethanol than in TFE this result emphasizes the weak solvation of protons by TFE (19). Continuing this trend, alkali metal salts are very sparingly soluble in HFIP (18). 

The direct reduction of SbF5 in the absence of hydrocarbons by molecular hydrogen necessitates, however, more forcing conditions (50 atm, high temperature) which suggests that the protolytic ionization of alkanes proceeds probably via solvation of protonated alkane by SbF 5 and concurrent ionization-reduction (equation 14) ". ... 

The only solute species common to all solvents is the proton, and it is with respect to this species that any universal scale must be drawn up. The solvation of protons will occur to different extents in different solvents... 

Bagno, A., Boso, R.L., Ferrari, N. and Scorrano, G. (1995) Steric effects on the solvation of protonated di-ferf-butyl ketone and phenyl ferf-butyl ketone. J. Chem. Soc., Chem. Commun., 2053-2054. 

Many organic reactions involve acid concentrations considerably higher than can be accurately measured on the pH scale, which applies to relatively dilute aqueous solutions. It is not difficult to prepare solutions in which the formal proton concentration is 10 M or more, but these formal concentrations are not a suitable measure of the activity of protons in such solutions. For this reason, it has been necessaiy to develop acidity functions to measure the proton-donating strength of concentrated acidic solutions. The activity of the hydrogen ion (solvated proton) can be related to the extent of protonation of a series of bases by the equilibrium expression for the protonation reaction. 

These isomerization processes may be dependent on the nature of the solvent. For example, the rotational barrier of the tetrazathiapentalenes 15.15 (ca. 16 kcal moF ) is influenced by the donor or acceptor ability of the substituents X and Y through the S N short contacts.Solvents with acidic protons increase the magnitude of the barrier, whereas solvents that are good Lewis bases decrease the size of the barrier, owing to solvation of the transition state. 

In the meantime, it should not be forgotten that all the equations involving the proton have been written in a conventional, i.e., the most concise, way as the degree of solvation of the proton in a solvent such as HOAc is unknown (cf., reaction 4.53). 

Thermodynamically it can be stated, if the differences of solvation of the compounds X" and HX between two solvents are neglected, that the difference in the pK values of compound HX in the two solvents is completely determined by the difference in the proton affinities of the two solvents80 hence a comparison of the pjfifj, values of various compounds in the solvents 1,2-DCE, m-cresol, acetic acid, pyridine and water is worth considering (see Table 4.5)80. 

B. Influence of Solvation on the Composition of Protonated Clusters Mixed Cluster Systems... 

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