Hydrogen atoms from the decomposition of hexamethylethane were reacted with chlorobenzene, o-dichlorobenzene, p-dichlorobenzene, and 1,2,3-trichlorobenzene in the presence of toluene or 1,3,5-1rimethylbenzene in single-pulse shock tube experiments. Using the rate expression for the displacement of the methyl group from the methylated aromatics as standards we find k(H + C6H5C1 -C6H6 + Cl) = (2.2 X 1010) exp(-4531/7) L/(mol-s), k(H + o-C6H4C12 -C6HSC1 + Cl) = (9.2 X 1010) exp(-5196/T) L/(mol-s), fc(H + p-C6H4Cl2 -C6H5C1 + Cl) = (4.6 X 1010) exp(-4541/T) L/(mol-s), /t(H + ,1,2,3-C6H3C13o-C6H4C1 + Cl) = (1.9 X 1010) exp(-2954/T) L/(mol-s), and k(H + 1,2,3-C6H3C13w-C6H4C1 + Cl) = (3.7 X 109) exp(-1856/7) L/(mol-s) at temperatures of 1050-1150 K and pressures between 2.5 and 3.2 atm. In this temperature range the relative rate constants on a per-chlorine basis for the five processes are 1:1.15:1.05:1.8:2.4. The absolute uncertainty in the rate expressions are of the order of 8 kj in the activation energy and a factor of 2.5 in the A factor. The relative rate constants have an uncertainty of no more than a factor of 1.1. Rate expressions for the reverse chlorination processes have been calculated to be k(Cl + C6H6 -* C6H5C1 + ) = (4.7 x 10*°) exp(-13453/7) L/(mol-s), k(Cl + C6H5C1 -» o-C6H4C12 + ) = (2.9 X 1010) exp(-15075/7') L/(mol-s), and k(Cl + C6H5C1p-C6H4Cl2 + ) = (8.8 X 109) exp(-13614/7) L/mol-s.
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