Development of a New Flow Reactor for Kinetic Studies. Application to the Ozonolysis of a Series of Alkenes

A new flow reactor has been developed to study ozonolysis reactions at ambient pressure and room temperature (297 +/- 2 K). The reaction kinetics of O-3 with 4-methyl-1-pentene (4M1P), 2-methyl-2-pentene (2M2P), 2,4,4-trimethyl-1-pentene (tM1P), 2,4,4-trimethy1-2-pentene (tM2P) and a-pinene have been investigated under pseudo-first-order conditions. Absolute measurements of the rate coefficients have been carried out by recording O-3 consumption in excess of organic compound. Alkene concentrations have been determined by sampling adsorbent cartridges that were thermodesorbed and analyzed by gas-chromatography coupled to flame ionization detection. Complementary experimental data have been obtained using a 250 L Teflon smog chamber. The following ozonolysis rate coefficients can be proposed (in cm(3) molecule(-1) s(-1)): k(4MIP) (8.23 +/- 0.50) x 10(-18), k(2M2p) = (4.54 +/- 0.96) X 10(-16), ktmir. = (1.48 +/- 0.11) X 10(-17), = (1.25 +/- 0.10) X 10(-16), and = (1.29 +/- 0.16) x 10(-16), in very good agreement with literature values. The products of tM2P ozonolysis have been investigated, and branching ratios of (21.4 +/- 2.8)% and (73.9 +/- 7.3)% have been determined for acetone and 2,2-dimethyl-propanal, respectively. Additionally, a new nonoxidized intermediate, 2-methyl-1-propene, has been identified and quantified. A topological SAR analysis was also performed to strengthen the consistency of the kinetic data obtained with this new flow reactor.