Unimolecular decomposition of the long-lived complex formed in the reaction F+C4H8

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Abstract
The reactions of fluorine atoms with four butene isomers have been studied by the method of crossed molecular beams. Angular distributions and velocity spectra of products formed by substitution of F for CH3 and H have been measured. Relative rates for CH3 and H substitution are in qualitative agreement with RRKM predictions for competitive rates of dissociation of a fluorobutyl complex. Quantitative agreement is possible with minor adjustments in the exothermicities or barriers to dissociation. The kinetic energy distributions of the products, on the other hand, are not in accord with those predicted by statistical theories of unimolecular reactions. The results suggest that the assumption of randomization of internal energy breaks down at least for complex configurations close to the transition state where coupling between separating fragments is still strong enough to allow appreciable nonrandom mixing of translational energy with rotations and vibrations of the larger fragment.