Infrared photochemistry of specifically deuterated bicyclopropyl. A direct test of statistical unimolecular rate theory applied to branching ratios in multiphoton dissociation

Abstract

The infrared photochemical decomposition of bicyclopropyl-d/sub 4/, specifically deuterated on one ring, has been examined. The molecule incorporates two reactive moieties that are differentiated only by isotopic substitution, hydrogenated and deuterated cyclopropane rings. Since statistical theories predict essentially equivalent rates of decomposition of each ring at any internal energy, the branching ratio constitutes a direct probe for nonstatistical effects. From a determination of the deuterium distribution in the single-ring cleaved product, allylcyclopropane, a branching ratio, k/sub H//k/sub D/ = 1.03 +- 0.08, is calculated. This is in good agreement with the statistical prediction and provides direct chemical evidence for the lack of significant nonrandom chemistry in the multiphoton infrared photochemistry of bicyclopropyl under the conditions of these experiments. 6 figures, 1 table.