Theoretical estimates of sulfoxyanion triple-oxygen equilibrium isotope effects and their implications

Very often in order to understand physical and chemical processes taking place among several phases fractionation of naturally abundant isotopes is monitored. Its measurement can be accompanied by theoretical determination to provide a more insightful interpretation of observed phenomena. Predictions are challenging due to the complexity of the effects involved in fractionation such as solvent effects and non-covalent interactions governing the behavior of the system which results in the necessity of using large models of those systems. This is sometimes a bottleneck and limits the theoretical description to only a few methods. In this work vapour pressure isotope effects on evaporation from various organic solvents (ethanol, bromobenzene, dibromomethane, and trichloromethane) in the pure phase are estimated by combining force field or self-consistent charge density-functional tight-binding (SCC-DFTB) atomistic simulations with path integral principle. Furthermore, the recently developed Suzuki-Chin path integral is tested. In general, isotope effects are predicted qualitatively for most of the cases, however, the distinction between position-specific isotope effects observed for ethanol was only reproduced by SCC-DFTB, which indicates the importance of using non-harmonic bond approximations. Energy decomposition analysis performed using the symmetry-adapted perturbation theory (SAPT) revealed sometimes quite substantial differences in interaction energy depending on whether the studied system was treated classically or quantum mechanically. Those observed differences might be the source of different magnitudes of isotope effects predicted using these two different levels of theory which is of special importance for the systems governed by non-covalent interactions.

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Faculty Opinions recommendation of Inverse enzyme isotope effects in human purine nucleoside phosphorylase with heavy asparagine labels.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.733476941.793549593 ◽

2018 ◽

Author(s):

Andrey Kovalevsky ◽

Steven Dajnowicz

Keyword(s):

Purine Nucleoside Phosphorylase ◽

Isotope Effects ◽

Purine Nucleoside ◽

Nucleoside Phosphorylase

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Discoveries of Mass Independent Isotope Effects in the Solar System: Past, Present and Future

Reviews in Mineralogy and Geochemistry ◽

10.2138/rmg.2021.86.02 ◽

2021 ◽

Vol 86 (1) ◽

pp. 35-95

Author(s):

Mark H. Thiemens ◽

Mang Lin

Keyword(s):

Solar System ◽

Isotope Effects

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Mechanism of hydration and isomerisation of 4-ethylidene-2,6-di-tert-butyl-2,5-cyclohexadien-1-one. Kinetics, acid-base catalysis and solvent deuterium isotope effects

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19790110 ◽

1979 ◽

Vol 44 (1) ◽

pp. 110-122 ◽

Cited By ~ 2

Author(s):

Jiří Velek ◽

Bohumír Koutek ◽

Milan Souček

Keyword(s):

Aqueous Medium ◽

Rate Equation ◽

Kinetic Data ◽

Isotope Effects ◽

Base Catalysis ◽

Quinone Methide ◽

Reaction Products ◽

Acid Base ◽

Deuterium Isotope Effects ◽

Hydroxybenzyl Alcohol

Competitive hydration and isomerisation of the quinone methide I at 25 °C in an aqueous medium in the region of pH 2.4-13.0 was studied spectrophotometrically. The only reaction products in the studied range of pH are 4-hydroxybenzyl alcohol (II) and 4-hydroxystyrene (III). The form of the overall rate equation corresponds to a general acid-base catalysis. The mechanism of both reactions for three markedly separated pH regions is discussed on the basis of kinetic data and solvent deuterium effect.

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