Study on the reaction mechanism of chlorobenzene with hydrogen peroxide in aqueous solutions initiated by 266 nm UV light

The reaction microscopic mechanism of chlorobenzene with hydrogen peroxide in aqueous solutions under different conditions was studied by laser flash photolysis. The main characteristic peaks in these transient absorbance spectra were assigned and the build-up/decay trends of several transient species were investigated. OH free radical can be produced through the 266 nm laser flash photolysis of hydrogen peroxide in aqueous solutions. The reaction of OH free radical and chlorobenzene produces C6H5Cl-OH adduct with a rate constant of (5.89 +/- 0.65) x 10(9) (L center dot mol(-1)center dot s(-1)) in the approximately neutral solution (pH approximate to 6) or (7.07 +/- 0.61) X 10(9) L center dot mol(-1)center dot s(-1) in acid (pH=1.5) solution, while its rate constant is about (4.34 +/- 0.51)X 10(9) L center dot mol(-1)center dot s(-1) in the basic (pH=9) solution. In the approximately neutral solution (pH approximate to 6) or in acid (pH = 1.5) solution, the intermediate can decay from itself gradually through a second-order reaction with 2k/epsilon l=1.1 X 10(6) s(-1). While in the basic (pH=9) solution, its decay trend shows pseudo-first-order rate constant of 2.11 X 10(5) s(-1). The C6H5Cl-OH adduct will be able to react with O-2 to form C6H5Cl-OHO2.