On the Origin of Conformational Kinetic Isotope Effects


  • D.J.O. thanks Pomona College for supporting this research. M.P.M. acknowledges NIGMS (GM87706-01).


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Neatly dissected: The computed conformational kinetic isotope effects (KIEs) for biphenyls 1 and 2 (X=D or H) are in good agreement with experimental values and have been partitioned according to the Bigeleisen–Mayer and ΔHS approaches. In [D8]-1 the KIE is dominated by a normal entropic contribution which overshadows an enthalpic contribution determined by Hvib and not HZPE. The inverse isotope effect in [D6]-2 is governed by an enthalpic zero-point energy term (HZPE) working against a normal entropic contribution.