CCl_4的光解微观机制研究

Study On the Laser Flash Photolysis of Carbon Tetrachloride

利用激光光解瞬态吸收光谱技术,研究有氧和无氧条件下CCl4的激光光解.结果表明,在248nm激光作用下,CCl4发生了单光子吸收,反应生成狖CCl4-Cl狚σ电荷转移复合物、(CCl3+…Cl-)离子对、CCl3O2过氧自由基等瞬态物种,它们的衰减过程是表观一级反应.狖CCl4-Cl狚σ电荷转移复合物在有氧/无氧条件下的拟合衰减速率常数分别是3.38×106s-1和3.65×106s-1,它的形成不受氧气含量影响.(CCl3+…Cl-)离子对在有氧/无氧条件下的拟合衰减速率分别为3.73×107s-1和3.02×107s-1,它的形成也不受氧气含量影响,CCl3O2过氧自由基需在有氧条件下形成,拟合衰减速率是2.32×104s-1.

Carbon tetrachloride was subjected to transient laser flash photolysis in the presence or absence of oxygen, transient absorption spectra were observed and analyzed. The experiment indicates that a series of micro-reactions occurred under 248 nm laser by a single photon absorption of CCl4, including the dissociation of the solvent and the formation of sophisticated substances - {CCl4 - Cl} sigma charge transfer complex, (CCl3+ ... Cl-) ion pair and CCl3O2. These absorptions decay according to the first order kinetics, and the decay rate constants of {CCl4 - Cl} sigma charge transfer complex were obtained to be 3.38 x 10(6) s(-1) and 3. 65 x 10(6) s(-1) in the presence and absence of oxygen, respectively, and its production has nothing to do with the oxygen. The decay rate constants of (CCl3+ (...) Cl-) were also gained to be 3.73 x 10(7) s(-1) and 3.02 x 10(7) s(-1) in the presence and absent of oxygen, respectively. However, CCl3O2 exists only in the presence of oxygen with a decay rate constant of 2.32 x 10(4) s(-1).