The specific rate constant for opening the cyclopentyl radical has been determined to be 1014.5 exp –37 700/RT s−1. The energy of activation indicates that any eclipsed pairs of H atoms in the cyclic radical are not de-eclipsed in the activated complex. No evidence for the resulting five-membered linear radical can be found, only evidence for its breakdown products, allyl radical and ethylene.The disproportionation/combination ratio for methyl and cyclopentyl radicals is about 0.3. The energy of activation for methyl abstracting a hydrogen atom from cyclopentane has been confirmed as about 9.5 kcal/mole.Cyclopentyl radical also loses a hydrogen atom to form cyclopentene. The kinetic parameters are difficult to obtain because of radical–radical reactions which form cyclopentene. An analysis of the results indicates an energy of activation at least equal to that for opening the cyclopentyl ring.Evidence is presented to support the view that the cyclopentyl radical loses a molecule of hydrogen to form the resonance-stablized cyclopentenyl radical with an energy of activation close to that for opening the ring, and a pre-exponential factor about 1/10 of that for the opening of the ring.
Facet-dependent performance of BiOBr for photocatalytic reduction of Cr(vi)
