GAS-PHASE THERMOLYSIS OF ALLYLPHOSPHINES, KINETIC-STUDY

Diallylphenyl, allylbenzylphenyl and allylmethylphenyl phosphines were pyrolized in a stirred-flow reactor at 380-429-degrees-C/7-20 torr, using toluene as carrier gas. The reaction products were propene, 1-phospha-1,3-butadiene, 1-phospha-1,2-diphenylethylene and 1-phosphaethylene. The phospha-alkenes formed evolve into cyclo addition products. The propene elimination reaction showed first-order kinetics with rate coefficients following the Arrhenius equations: Diallylphenylphosphine: k(s-1) = 10(10.57 +/- 0.31) exp(-143 +/- 4 kJ/mol.RT) Allylbenzylphenylphosphine: k(s-1) = 10(9.71 +/- 0.47) exp (-135 +/- 6 kJ/mol.RT) Allylmethylphenylphosphine: k(s-1) = 10(9.61 +/- 0.61) exp(-144 +/- 9 kJ/mol.RT) A six-center cyclic transition state unimolecular reaction mechanism, consistent with the above Arrhenius parameters, is proposed for the propene elimination reaction.