Grishma Singh

Current textbooks explain deuterium (D) kinetic isotope effects (KIEs) using the semiclassical transition state (TS) theory. KIEs originate from the isotopic zero-point energy difference at the reactant versus TS states. Within the semiclassical theory, KIEs range from 2 to 7, and the isotopic activation energy difference (ΔEa = EaD – EaH), which reflects temperature (T) dependence of KIEs, falls in between 1.0 and 1.2 kcal/mol.

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Conflicts of Interest The authors declare no conflicts of interest. Supporting Information Filename Description poc70002-sup-0001-Supporting_Information.pdfPDF document, 511.9 KB Table S1. Gas-phase free energies (G°) of the optimized structures for KIE computationsa. Table S2. Free energies (G°) and DADPRC ’ s of the optimized PRC structures in acetonitrilea. References 1 and , “Enzyme Catalysis: Beyond Classical Paradigms,” Accounts of Chemical Research 31 (1998): 397–404.