Kinetic studies of the self-reaction and reaction with HO2 of a tertiary beta-brominated peroxy radical between 298 and 393 K

The kinetics of reactions of the tertiary beta -brominated peroxy radical B rC(CH3)(2)C(CH3)(2)O-2 (2-bromo-1,1,2-trimethylpropylperoxy) have been stud ied using the laser flash photolysis technique. photolysing HBr at 248 nm i n the presence of O-2 and 2,3-dimethylbut-2-ene. At room temperature. a rat e constant of (2.0 +/- 0.8) x 10(-14) cm(3) molecule(-1) s(-1) was determin ed for the BrC(CH3)(2)C(CH3)(2)O-2 self-reaction. The reaction of BrC(CH3)( 2)C(CH3)(2)O-2 with HO2 was investigated in the temperature range 306-393 K , yielding the following Arrhenius expression: k(BrC(CH3)(2)C(CH3)(2)O-2 HO2) = (2.04 +/- 0.25) X 10(-12) exp[(501 +/- 36)K/T] cm(3) molecule(-1) s( -1) giving by extrapolation (1.10 +/- 0.13) X 10(-11) cm(3) molecule(-1) s( -1) at 298 K. These results confirm the enhancement of the peroxy radical s elf reaction reactivity upon beta -substitution, which is similar for Br an d OH substituents. in contrast, no significant effect of substituent has be en observed on the rate constant for the reactions of peroxy radicals with HO2. The global uncertainty factors on rate constants are equal to nearly 2 For the self-reaction and to 1.35 for the reaction with HO2. (C) 2000 John Wiley & Sons, Inc.