title: Deuterium and hydrogen tunneling in the hydrogenation of 4-oxocyclohexa-2,5-dienylidene.
abstract: 4-Oxocyclohexa-2,5-dienylidene is a highly reactive triplet ground state carbene that is hydrogenated in solid H2, HD, and D2 at temperatures as low as 3 K. The mechanism of the insertion of the carbene into dihydrogen was investigated by IR and EPR spectroscopy and by kinetic studies. H or D atoms were observed as products of the reaction with H2 and D2, respectively, whereas HD produces exclusively D atoms. The hydrogenation shows a very large kinetic isotope effect and remarkable isotope selectivity, as was expected for a tunneling reaction. The experiments, therefore, provide clear evidence for both hydrogen tunneling and the rare deuterium tunneling in an intermolecular reaction.
authors.affiliation: Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44781 Bochum (Germany).
authors.forename: Stefan
authors.initials: S
authors.lastname: Henkel
authors.forename: Melanie
authors.initials: M
authors.lastname: Ertelt
authors.forename: Wolfram
authors.initials: W
authors.lastname: Sander
keywords: EPR spectroscopy; IR spectroscopy; carbenes; hydrogen activation; matrix isolation