Itou Y, Mori S, Udagawa T, Tachikawa M, Ishimoto T, Nagashima U. Quantum Treatment of Hydrogen Nuclei in Primary Kinetic Isotope Effects in a Thermal [1,5]-Sigmatropic Hydrogen (or Deuterium) Shift from (Z)-1,3-Pentadiene.
J Phys Chem A 2006;
111:261-7. [PMID:
17214462 DOI:
10.1021/jp065759x]
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Abstract
The geometric and kinetic isotope effects (GIE and KIE) for thermal [1,5]-sigmatropic H and D shifts of (Z)-1,3-pentadiene were studied by including the direct quantum effect of the migrating H or D nucleus in the multi-component molecular orbital-Hartree-Fock (MC_MO-HF) method. Based on the results, the C(1)-D bond lengths are 0.007 Angstrom shorter than the C1-H bond lengths in both the reactant (A) and the transition states (TS), whereas other bond lengths resemble those between H and D. The ratio of the rate constant (k(H)/k(D)) of the reaction for the thermal [1,5]-H and D shifts determined using the MC_MO-HF method (8.28) is closer to the experimental value (12.2) than that determined using either the conventional restricted Hartree-Fock (4.10) or restricted Møller-Plesset second-order perturbation (3.79) methods.
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