KINETIC AND PRIMARY PRODUCT STUDIES OF THE REACTION OF O (P-3) WITH STYRENE IN THE GAS-PHASE

The rates of the reaction of styrene with atomic oxygen have been measured in a discharge flow system with mass spectrometric detection. The measurements were carried out under oxygen atom excess in the temperature range 298 K < T < 873 K. The main reaction channel at room temperature is O atom addition to the vinyl side chain, yielding as main product (identified by mass spectrometric product analysis) styrene oxide. Towards higher temperatures O atom addition to the aromatic ring as a second reaction channel becomes more important. Using Hammett plots the following Arrhenius expressions for the addition to the aromatic ring (k(ar)) and to the alkene double bond (k(db)) of the side chain can be derived: k(ar)(T) = (1.70 +/- 0.34) . 10(13) . exp(-2051 +/- 205/T) cm3 mol-1 s-1 k(dp)(T) = (0.14 +/- 0.03) . 10(13) . exp(+198 +/- 20/T) cm3 mol-1 s-1. First experiments with indene give similar results, showing a somewhat higher reactivity for this molecule compared to styrene.