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 data are available from the literature, including the observed kinetic isotope effects. For both cases the computed kinetic isotope effect was significantly smaller than that observed. These results provide further support for the presence of tunneling in thermal, antarafacial [1,7]-hydrogen shift reactions.