Computational support for tunneling in thermal [1,7]-hydrogen shift reactions

Density functional calculations have been performed for the [1,7]-hydrogen shift in two substituted 1,3,5-heptatrienes (1 and 9) for which kinetic dat a are available from the literature, including the observed kinetic isotope effects. For both cases the computed kinetic isotope effect was significan tly smaller than that observed. These results provide further support for t he presence of tunneling in thermal, antarafacial [1,7]-hydrogen shift reac tions.