ON THE KINETICS OF REACTIONS OF HYDROGEN-ATOMS WITH CHLORINATED AND BROMINATED HYDROCARBONS

The reactions of hydrogen atoms with several halogenated hydrocarbons have been investigated in an isothermal discharge flow reactor at a te mperature of 298 K and a pressure of 4 mbar. Overall rate constants we re determined by detecting the decrease of the halocarbon for differen t reaction times, using quadrupole mass spectrometry. The following ra te constants (in cm(3) mol(-1) s(-1)) were obtained: CH3Cl, (5.6 +/- 2 .8). 10(8); C2H5Cl, (1.4 +/- 0.7). 10(9); C2H5Br, (5.1 +/- 2.5). 10(10 ); C6H5CH2Cl, (2.2 +/- 1.1). 10(10); C6H5CH2Br, (9.6 +/- 4.8). 10(10); C6H5CH2CH2Cl, (8.4 +/- 4.2). 10(9); and C6H5CH2CH2Br, (2.9 +/- 1.4). 10(10). Trends in reacivity are verified and branching ratios between halogen and hydrogen abstraction are estimated by means of simple bond -energy bond-order (BEBO) calculations.