Energy of proton transfer

Calculate the energy of proton transfer from trimethylsulfoxonium cation to its ylide, relative to that for trimethylsulfonium cation to its ylide, i.e. 

Schuurmann, G., Quantum chemical analysis of the energy of proton transfer from phenol and chlorophenols to H20 in the gas phase and in aqueous solution, J. Chem. Phys., 109, 9523-9528, 1998b. 

A second class [ 16] is one that may enjoy increased interest in the future because of the presence of one of its members in the first industrial IL process [lb], and also because of the new finding that its members can have aqueous solution-like conductivities [17] and can serve as novel electrolytes for fuel cells [18]. This class is closely related to the first but differs in that the cation has been formed by transfer of a proton from a Br0nsted acid to a Br0nsted base. The process is reversible, depending on how large the free energy of proton transfer is. When the gap across which... 

The activation energy of proton transfer has been estimated to be E < 2 kcal/mol (4) according to... 

SO3- groups will provide lower activation energies of proton transfer. 

Activation parameters of the organosilicon compounds reactions with OH groups on the pyrogenic silica surface (A, pre-exponential factor and observed activation energy on free surface) [79-81], the estimated heat of adsorption complex formation (Qads) and activation energy of proton transfer (E j ) from [49]... 

Table 4. The enthalpy values of hydrogen bonded complexes of acids RAH with ( 03)280, coalescence temperature Tc, and activation energy of proton transfer in the complex...

Now let us return to the approaches connected with the estimation of the primary medium effect for protons, log y0 n+, that are used for obtaining quantitative information on the acidity of pure protolytic or aprotic solvents relative to the standard solution of a strong acid in water. From the thermodynamics, these are known to be a measure of the Gibbs free energy of proton transfer from the standard solution in water to the one in a non-aqueous solvent (M). This parameter is connected with the energy of proton resolvation in the following way ... 

Standard Free Energies of Proton Transfer and Solvation in Aqueous Aci< General Description. ... 

STANDARD FREE ENERGIES OF PROTON TRANSFER AND SOLVATION IN AQUEOUS ACID... 

In other words, the medium-specific contribution is not easily measured or quantified for probe molecules in interaction with solid surfaces. Moreover, in the case of microporous solids, the short-distance interactions known as "confinement effects" are even more difficult to evaluate. In all comparisons of experimental data one should be aware that the reactivity of probe base molecules is largely influenced by the size of adsorbates and micropore dimensions. As a result, the acidity scales based on the free energy of proton transfer to a specific base are expected to depend on the choice of reference base. This fact has been confirmed experimentally, as calorimetric heats of adsorption of various bases on, e.g., zeolites, depend on the base chosen. For example, a ZH zeolite may be a stronger acid... 

It was possible to rationalize the family of Arrhenius plots measured for Nafion 117 at different water contents [46]. Under an assumption that the surface conductivity has higher activation energy, supported by microscopic considerations in Refs. 40, 43, the Arrhenius slope should become steeper with the decreasing amount of water in the membrane [39], that is, the smaller the amount of the bulk water that we have in pores. Activation energies obtained from these plots are 0.1 eV for the largest possible water contents (Activation energies of proton transfer in water, estimated from nuclear magnetic resonance relaxation times, are 0.1 eV [47].) and 0.3-0.4eV at small water contents. How to rationalize this variation. ... 

The activation energies of proton transfer reactions in water. J. Am. Chem. Soc.,... 

There is also a relationship between the dihydrogen bond strength and the activation free energy of proton transfer. The latter decreases with the increase of -AT/qjjb (Fig. 8.5). This experimental trend is also predicted by theoretical calculations, which show the ultimate disappearance of the dihydrogen bond minimum and a spontaneous proton transfer with the increase of dihydrogen bond strength [38-40]. 

Comparison of experimental and theoretical (STO-3G) energies of proton transfer in the gas phase ... 

ShuMa SK, Kumar A (2013) Probing the acidity of carboxyhc acids in protic ionic liquids, water, and their binary mixtures activation energy of proton transfer. J Phys Chem B 117(8) 2456-2465. doi 10.1021/jp310927w... 

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