Recoil tritium reactions with cyclohexene and alkenes. Determination of rate parameters

Kinetic rate parameters can be determined from recoil tritium reaction studies although the energy distribution of the reacting tritium atoms is not known. T is produced by /sup 3/He(n,p)T. Recoil T-for-H substitution on cyclohexene gives excited cyclohexene-t molecules. The dependence of product yield on pressure (in the hexene-t molecules decomposed unimolecularly to give ethylene-t and butadiene-t with an apparent rate constant (at 135 deg ) of 5 x 10/ sup 6/ s/sup -1/. The s parameter in the RRK (Rice, Ramsperger, and Kassel) treatment of the unimolecular decomposition of cyclohexene was determined as s = 24. Similarly, the pressure dependence of product yield showed that cyclohexyl-t radicals which are fornaed by recoil T atom addition to cyclohexene decomposed unimolecularly to give n-hexene-t, 1-butene-t, and methane-t with rate constant 8 x 10/sup 3/, 3 x 10/sup 4/, and 5 x 10/sup 2/ s/sup -1/, respectively . The relative nate of abstraction vs addition of radicals in alkenes was determined from the scavenger dependence of the yields of products with a nadical precursor. (40 references) (auth)