Formation of deuterium and hydrogen atoms in the pyrolysis of benzene-d6 and chlorobenzene behind shock waves

From the measurements of H atoms during pyrolysis of chlorobenzene under similar conditions at 1570-1790K, the first-order rate constant for the dissociation of chlorobenzene to chlorine atoms and phenyl radicals was found to be about an order of magnitude greater than that for the pyrolysis of C/sub 6/D/sub 6/, and a rate constant still another order of magnitude greater was noted for the dissociation of phenyl radicals to H atoms and other products. From this information, a rate constant was derived for the dissociation of benzene-d/sub 6/ to phenyl-d/sub 5/ and D atoms. The rate constant for the H-D exchange reaction on benzene was determined over the temperature range of 300-1400K by combining results of this work with that of others at lower temperatures. A very simple kinetic model based on a reaction chain with H as carrier can relate the data presented from this work to other shock-tube work at higher benzene concentrations.