Kinetics and mechanism of the gas phase reaction of Cl atoms and OH radicals with bromobenzene

Relative rate techniques were used to study the kinetics and mechanism of the reaction of Cl atoms and OH radicals with bromobenzene (C6H5Br) in 20–700 Torr of N2, O2, or air diluent at 295±2 K. Using the observed rate constant ratios k(C6H5Br+Cl)/k(C2H5Cl+Cl)=1.56±0.05 and k(C6H5Br+Cl)/k(C2H6+Cl)=0.24±0.01, the C6H5Br+Cl rate constant is determined to be k(C6H5Br+Cl)=(1.32±0.20)×10−11 cm3 molecule−1 s−1 giving exclusively C6H5Cl through a displacement mechanism. Using the observed rate constant ratios k(C6H5Br+OH)/k(C6H6+OH)=0.77±0.06 and k(C6H5Br+OH)/k(C2H4+OH)=0.11±0.004, the C6H5Br+OH rate constant is determined to be k(C6H5Br+OH)=(9.37±2.04)×10−13 cm3 molecule−1 s−1. The product expected from a displacement mechanism, phenol, was not observed (<10% yield).