Gas phase thermolysis of allylphosphines, kinetic study

Diallylphenyl, allylbenzylphenyl and allylmethylphenyl phosphines were pyrolized in a stirred‐flow reactor at 380–429°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) = 1010.57 ± 0.31 exp(‐143 ± 4 kJ/mol.RT) Allylbenzylphenylphosphine: k(s−1) = 109.71 ± 0.47 exp(‐135 ± 6 kJ/mol.RT) Allylbenzylphenylphosphine: k(s−1) = 109.61 ± 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.