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Experimental evidence for heavy-atom tunneling in the ring-opening of cyclopropylcarbinyl radical from intramolecular 12C/13C kinetic isotope effects.

ABSTRACT: The intramolecular (13)C kinetic isotope effects for the ring-opening of cyclopropylcarbinyl radical were determined over a broad temperature range. The observed isotope effects are unprecedentedly large, ranging from 1.062 at 80 degrees C to 1.163 at -100 degrees C. Semiclassical calculations employing canonical variational transition-state theory drastically underpredict the observed isotope effects, but the predicted isotope effects including tunneling by a small-curvature tunneling model match well with experiment. These results and a curvature in the Arrhenius plot of the isotope effects support the recently predicted importance of heavy-atom tunneling in cyclopropylcarbinyl ring-opening.

SUBMITTER: Gonzalez-James OM

PROVIDER: S-EPMC2935944 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Experimental evidence for heavy-atom tunneling in the ring-opening of cyclopropylcarbinyl radical from intramolecular 12C/13C kinetic isotope effects.

Gonzalez-James Ollie M OM Zhang Xue X Datta Ayan A Hrovat David A DA Borden Weston Thatcher WT Singleton Daniel A DA

Journal of the American Chemical Society 20100901 36

The intramolecular (13)C kinetic isotope effects for the ring-opening of cyclopropylcarbinyl radical were determined over a broad temperature range. The observed isotope effects are unprecedentedly large, ranging from 1.062 at 80 degrees C to 1.163 at -100 degrees C. Semiclassical calculations employing canonical variational transition-state theory drastically underpredict the observed isotope effects, but the predicted isotope effects including tunneling by a small-curvature tunneling model mat ...[more]

PMID: 20722415

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