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Hydrogen Tunnelling as a Probe of the Involvement of Water Vibrational Dynamics in Aqueous Chemistry?
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Kinetic Isotope Effects and Hydrogen Tunnelling in PCET Oxidations of Ascorbate: New Insights into Aqueous Chemistry?

Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10 000 Zagreb, Croatia
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Academic Editor: Poul Erik Hansen
Molecules 2020, 25(6), 1443; https://doi.org/10.3390/molecules25061443
Received: 17 February 2020 / Revised: 19 March 2020 / Accepted: 21 March 2020 / Published: 23 March 2020
(This article belongs to the Special Issue Isotope Effects 2019)
Recent experimental studies of kinetic isotope effects (KIE-s) and hydrogen tunnelling comprising three proton-coupled electron transfer (PCET) oxidations of ascorbate monoanion, (a) in aqueous reaction solutions, (b) in the mixed water-organic cosolvent systems, (c) in aqueous solutions of various salts and (d) in fairly diluted aqueous solutions of the various partial hydrophobes are reviewed. A number of new insights into the wealth of the kinetic isotope phenomena in the PCET reactions have been obtained. The modulation of KIE-s and hydrogen tunnelling observed when partially hydrophobic solutes are added into water reaction solution, in the case of fairly diluted solutions is revealed as the strong linear correlation of the isotopic ratios of the Arrhenius prefactors Ah/Ad and the isotopic differences in activation energies ΔEa (D,H). The observation has been proposed to be a signature of the involvement of the collective intermolecular excitonic vibrational dynamics of water in activation processes and aqueous chemistry. View Full-Text
Keywords: kinetic isotope effects; ascorbate PCET reactions; hydrogen tunnelling; water vibrational dynamics; activation processes kinetic isotope effects; ascorbate PCET reactions; hydrogen tunnelling; water vibrational dynamics; activation processes
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Karković Marković, A.; Jakobušić Brala, C.; Pilepić, V.; Uršić, S. Kinetic Isotope Effects and Hydrogen Tunnelling in PCET Oxidations of Ascorbate: New Insights into Aqueous Chemistry? Molecules 2020, 25, 1443.

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