Proton Affinity

If we use B3LYP/VTZ+1 harmonics scaled by 0.985 for the Ezpv rather than the actual anharmonic values, mean absolute error at the W1 level deteriorates from 0.37 to 0.40 kcal/mol, which most users would regard as insignificant. At the W2 level, however, we see a somewhat more noticeable degradation from 0.23 to 0.30 kcal/mol - if kJ/mol accuracy is required, literally every little bit counts . If one is primarily concerned with keeping the maximum absolute error down, rather than getting sub-kJ/mol accuracy for individual molecules, the use of B3LYP/VTZ+1 harmonic values of Ezpv scaled by 0.985 is an acceptable fallback solution . The same would appear to be true for thermochemical properties to which the Ezpv contribution is smaller than for the TAE (e.g. ionization potentials, electron affinities, proton affinities, and the like). 

Synaptosomal particles have a high-affinity proton-... 

Table 5 Average Absolute Deviations (in kcal/mol) from Experiment of Various Composite Ab Initio Molecular Orbital Methods for Ionization Energies, Electron Affinities, Proton Affinities, and Enthalpies of Formation in the G2/97 Test Set"... 

Results in parentheses use B3LYP/6-31G geometries and 0.96 scaled frequencies. As can be seen, the predicted ionization potentials, electron affinities, proton affinities, and enthalpies are not highly sensitive to the molecular geometries and vibrational frequencies adopted. 

Boll M, Herget M, Wagener M, et al. Expression cloning and functional characterization of the kidney cortex high-affinity proton-coupled peptide transporter. Proc Natl Acad Sci U S A 1996 93 284-289. 

Calculated ionization energies, electron affinities, proton affinities, homolytic bond dissociation energies and other thermochemical quantities are tabulated and discussed. Agreement with experiment, where available, is very reasonable. 

Squires, R. R. Gas-Phase Transition Metal Negative Ion Chemistry, Chem. Rev. 1987, 87, 623-646. Tables with electron affinities, proton affinities, and metal-ligand bond dissociation enthalpies. 

Because of the large proton affinities protonated ions are quite stable. For example, if we use a thermodynamical argument the exothermicity of... 

A more universal measure of the basicity of a species is its gas-phase proton affinity (PA), which is defined in Equation (14.10). Like electron affinities, proton affinities are reported as positive values even though their enthalpies of reaction are always negative ... 

For the first time it is researched of classical quantum chemical method MNDO of modeling mechanism protonizataion of isobutylene—monomer of cationic pol5mierization. Showing, that he considerate some self-usual mechanism connection proton to olefin corresponding Morkovnikov s rule. Reaction exothermic and carry without a barrier character. Prize en-eigy in result of reaction -499 kDg/mol. Theoretical estimation of affinity proton to isobutylene -577 kDg/mol... 

Proton transfer mass spectrometiy (PTR-MS) was developed in 1995 at the University of Innsbruck by Werner Lindinger and his collaborators [48]. PTR-MS was able to utilize the ability of the H3O+ ion to transfer its proton (PA(H20) = 691 kJ mol ) to any analyte in air that has a higher proton affinity. Proton transfer reactions are invariably fast when exoergic and occnr at the collision rate [49], HjO is readily formed from a discharge in moist air it does not react with the bnlk constituents of air and is therefore a good indicator of the presence of any volatile species that may be present in a sample. Many of the organic molecnles that are important analytes in medicine, foods, and the environment have proton affinities (PAs) higher than that of H2O. Notable exceptions are the small alkanes, ethane, and acetylene. 

The NIST Chemistry WebBook supports a variety of searches for chemical species. Each search type has its own associated Web page. Search types currently available are genoal, physical property, formula, chemical name, CAS registry number, ion energetics, ionization energy, electron affinity, proton affinity, acidity, vibrational and electronic energy... 

Method Ionization potentials Electron affinities Proton affinities... 

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