266 nm光照下水溶液中氯苯与H2O2的反应机理研究

利用瞬态吸收光谱技术研究了不同条件下C₆H₅Cl与H₂O₂水溶液的激光闪光光解情况, 初步考察了其瞬态物种的生长和衰减等行为. 研究表明, •OH自由基和C₆H₅Cl反应生成C₆H₅Cl-OH adduct, 其反应速率常数在近中性、酸性条件下约为(5.89±0.65)×10⁹和(7.07±0.61)×10⁹ L•mol^－1•s^－1; 其衰减则符合双分子二级反应, 速率常数2k/εl＝1.1×10⁶ s^－1, 而在碱性时则为(4.34±0.51)×10⁹ L•mol^－1•s^－1, 衰减呈准一级反应, 速率常数为2.11×10⁵ s^－1. 在有氧条件下, O₂与C₆H₅Cl-OH adduct反应生成C₆H₅Cl-OHO₂ adduct, 其反应速率常数为6.8×10⁸ L•mol^－1•s^－1.

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)×10⁹ (L•mol^－1•s^－1) in the approximately neutral solution (pH≈6) or (7.07±0.61)×10⁹ L•mol^－1•s^－1 in acid (pH＝1.5) solution, while its rate constant is about (4.34±0.51)×10⁹ L•mol^－1•s^－1 in the basic (pH＝9) solution. In the approximately neutral solution (pH≈6) or in acid (pH＝1.5) solution, the intermediate can decay from itself gradually through a second-order reaction with 2k/εl＝1.1×10⁶ s^－1. While in the basic (pH＝9) solution, its decay trend shows pseudo-first-order rate constant of 2.11×10⁵ s^－1. The C₆H₅Cl-OH adduct will be able to react with O₂ to form C₆H₅Cl-OHO₂.