ON THE KINETICS OF REACTIONS OF HYDROGEN-ATOMS WITH AROMATIC-HYDROCARBONS

The kinetics of the reactions between H atoms and several aromatic hyd rocarbons has been studied in an isothermal discharge flow-reactor cou pled to a quadrupole mass-spectrometer. Overall rate coefficients at a temperature of 298 K and a pressure of 4 mbar (1.6 mbar in the case o f styrene and 2-propenylbenzene) were determined from the decrease of the hydrocarbon concentration for different reaction times. The follow ing values (in cm(3) mol(-1) s(-1)) were obtained: benzene, (3.4 +/- 1 .7).10(10); toluene, (8.1 +/- 4.0).10(10): ethylbenzene, (1.5 +/- 0.7) .10(11); styrene, (2.1 +/- 1.0).10(12); 2-propenylbenzene, (2.6 +/- 1. 3).10(12). The magnitudes of these rate coefficients as well as mechan istic aspects are discussed in view of the different substituents.