RATE COEFFICIENTS FOR THE GAS-PHASE REACTIONS OF BROMINE RADICALS WITH A SERIES OF ALKENES, DIENES, AND AROMATIC-HYDROCARBONS AT 298+ -2-K/

Using the relative kinetic method rate coefficients have been determin ed for the gas-phase reaction of bromine (Br) radicals with a series o f alkenes, chloroalkenes, dienes, and aromatic hydrocarbons in 1000 mb ar of synthetic air at 298 +/- 2 K. Both the UV photolysis of CH2Br2 ( lambda = 254 nm) and the visible photolysis of Br-2 (320 less than or equal to lambda less than or equal to 480) were used to generate Br ra dicals. For the alkenes and dienes the following rate coefficients wer e obtained (in units of 10-(12) cm(3) molecule(-1) s(-1)): trans-2-but ene 9.26 +/- 1.85; 2-methyl-1-butene 15.20 +/- 3.00; 2-methyl-2-butene 19.10 +/- 3.80; 2,3-dimethyl-2-butene 28.20 +/- 5.60; alpha-pinene 22 .20 +/- 4.40; beta-pinene 28.60 +/- 5.70; 1,3-butadiene 57.50 +/- 11.5 0; isoprene 74.20 +/- 14.80; and 2,3-dimethyl-1,3-butadiene 81.7 +/- 1 6.30. For the chloroalkenes and aromatic hydrocarbons the following ra te coefficients were obtained (in units of 10(-13) cm(3) molecule(-1) s(-1)): chloroethene 7.37 +/- 1.92; 1,1-dichloroethene 3.66 +/- 0.73; trichloroethene 0.90 +/- 0.18; tetrachloroethene less than or equal to 0.1; benzene less than or equal to 0.10; toluene less than or equal t o 0.10; p-xylene less than or equal to 0.10; and furan less than or eq ual to 0.10. With the exception of trans-2-butene, this study represen ts the first determination of the rate coefficients for all of the com pounds. (C) 1996 John Wiley & Sons, Inc.