355 nm光作用下C6F6-HNO2水溶液的反应机理

利用激光闪光光解-瞬态吸收光谱技术研究了355 nm 光作用下六氟苯(C6F6)-HNO2水溶液的反应机理, 探讨了中间产物及其动力学行为, 并对终产物进行了分析. 实验表明, C6F6可与HNO2光解产生的OH自由基反应生成加合物C6F6…OH, 二级反应速率常数为1.8×109 L·mol -1·s-1, 加合物吸收峰位置在250、270和400 nm处; C6F6…OH 加合物通过消除反应生成C6F5O·, 其表观生成常数为6.1×105 s-1. C6F6…OH与O2复合转化为C6F6OHO2, 二级反应速率常数为2.8×106 L·mol-1·s-1, C6F6OHO2峰位置与C6F6…OH 加合物相似. 终产物分析表明, OH自由基与六氟苯发生消除HF的反应而生成C6F5OH, 有O2时, 还产生四氟醌C6F4O2, 但无论有氧还是无氧体系, 均不发生硝基化反应.

Reaction Mechanism of C6F6-HNO2 Aqueous Solution under Irradiation at 355 nm

The reaction mechanism of C6F6-HNO2 aqueous solution was studied using laser flash photolysis-transient absorption spectrum technique under irradiation at 355 nm. The characteristic absorption peaks and the kinetic parameters of transient species were also investigated. The hydroxyl radical derived from the photolysis of HNO2 was added to hexafluorobenzene with a second-order rate constant of 1.8×109 L·mol-1·s-1 to form an adduct, C6F6…OH, which had absorption peaks at 250, 270, and 400 nm. The C6F6…OH adduct decayed by the elimination of HF to yield C6F5O· with an apparent first-order rate constant 6.1×105 s-1. In the presence of O2, C6F6…OH underwent a complex reaction with a rate constant of 2.8×106 L·mol-1·s-1 to form C6F6OHO2, which had the same absorption bands as C6F6…OH. The final products were identified using the GC-MS technique and the possible reaction pathways were also discussed.