Kinetics of the Reactions of Unsaturated Hydrocarbon Free Radicals (Vinyl, Allyl, and Propargyl) with Molecular Chlorine

Article abstract of DOI:10.1021/j100291a037

The kinetics of the reactions of three unsaturated free radicals (vinyl, allyl, and propargyl) with molecular chlorine have been studied by using a tubular reactor coupled to a photoionization mass spectrometer.The radicals were homogeneously generated by the pulsed photolysis of precursor molecules at 193 nm.The subsequent decays of the radical concentrations were monitored in real-time experiments as a function of Cl2 concentration to obtain the rate constants of these Cl atom metathesis reactions.Rate constants were measured as a function of temperature to obtain Arrhenius parameters.The following rate constant expressions were obtained (units of the preexponential factor are cm³ molecule^-1 s^-1, and activation energies are in kJ mol^-1; the temperature range covered in each study is also indicated): C2H3 + Cl2<1E-11.06 exp(2/RT), 298-435 K>; C3H3 + Cl2 <1E-10.56 exp(-28/RT), 525-693 K>; C3H5 + Cl2 <1E-10.81 exp(-18/RT), 487-693 K>.The factors governing the reactivity of polyatomic free radicals in these and other Cl atom transfer reactions with molecular chlorine are reviewed.