Gas chromatographic determination of rate constants in bimolecular gaseous reactions

Summary Rate constants for bimolecular reactions in the gas phase, under diffusion controlled conditions, can easily be determined by the reversed-flow gas chromatography (RF-GC) technique. The analysis of the diffusion band by means of a simple PC programme gives directly an apparent, second-order rate constant for gaseous reactions. By varying the amounts of the reactants, one can calculate the true order of the reaction and the true non-first-order rate constant of gaseous reactions. The calibration problem of the analytical techniques in non-first-order reaction kinetics is absent as are other disadvantages connected with carrier gas flow, peak shape and their instrumental spreading. The method can be used for atmospheric reactions and was applied in the gaseous reaction systems: SO₂+NO₂, SO₂+Br₂, C₆H₆+NO₂, C₆H₅CH₃+NO₂ and C₃H₆+NO₂ with various concentrations of reactants in nitrogen. The effect of the NO₂ concentration on the apparent second-order rate constant of C₂H₄+NO₂ at 333.2 K was also studied. Finally, the effect of sun light pre-irradiation of C₂H₂+NO₂ in nitrogen was investigated.