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Issue 15, 2017
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Unusual H/D isotope effect in isomerization and keto–enol tautomerism reactions of pyruvic acid: nuclear quantum effect restricts some rotational isomerization reactions

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Abstract

Isomerization and keto–enol tautomerism reactions of the pyruvic acid molecule have been investigated using the multicomponent B3LYP (MC_B3LYP) methods, which can take account of the nuclear quantum effect (NQE) of a light nucleus, such as a proton and a deuteron. While the conventional harmonic zero point vibrational energy (ZPVE) correction makes the activation energies of all the reactions in this system lower, a contrasting behavior is found in our MC_B3LYP results for several rotational reactions. In such cases, the H/D isotope effect on the activation energy is also completely opposite between harmonic ZPVE-corrected B3LYP and MC_B3LYP calculations. In our MC_B3LYP calculation, the activation energies of several C–C or O–H rotational reactions of H species are slightly higher than those of D species, since the NQE of a hydrogen-bonded proton strengthens the hydrogen-bonded interaction more than that of a deuteron, and, thus, the rotational motion of H species is restricted. Such an “unusual” H/D isotope effect on the activation energies can be observed only in the MC_B3LYP results. Our MC_B3LYP calculations clearly demonstrate that direct inclusion of NQE is indispensable to analyze H/D isotope effects on activation energies of not only hydrogen transfer reactions but also C–C and O–H rotational reactions in the isomerization and keto–enol tautomerism of pyruvic acid molecule.

Graphical abstract: Unusual H/D isotope effect in isomerization and keto–enol tautomerism reactions of pyruvic acid: nuclear quantum effect restricts some rotational isomerization reactions

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Publication details

The article was received on 16 Dec 2016, accepted on 27 Jan 2017 and first published on 31 Jan 2017


Article type: Paper
DOI: 10.1039/C6RA28271G
Citation: RSC Adv., 2017,7, 9328-9337
  • Open access: Creative Commons BY license
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    Unusual H/D isotope effect in isomerization and keto–enol tautomerism reactions of pyruvic acid: nuclear quantum effect restricts some rotational isomerization reactions

    T. Udagawa, K. Sugiura, K. Suzuki and M. Tachikawa, RSC Adv., 2017, 7, 9328
    DOI: 10.1039/C6RA28271G

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