多氯代二苯并呋喃(PCDFs)光解性质的量子化学研究

Quantum study on the photolysis behaviour of polychlorinated dibenzo-furans (PCDFs)

多氯代二苯并呋喃(PCDFs)是持久性有机污染物之一,其光化学降解是其主要的环境降解途径,本文是采用量子化学方法对PCDFs光解性质进行研究。本文采取AM1半经验量子化学计算方法计算了所有135种PCDFs的生成热和前线分子轨道能量,据此讨论了PCDFs分子光激发和还原脱氯难易程度与分子结构之间的关系。结果表明生成热可以成功解释PCDFs在水相中随着分子氯取代数目增加而光解速率降低的规律,而前线分子轨道能则可以解释正构烷烃溶剂中随氯原子取代数目增加而还原脱氯在降解机理中越占主导地位的规律,从而从量子化学的角度为实验结果提供了理论解释。

Polychlorinated dibenzofurans (PCDFs) is included in the blacklist of so-called persistent organic pollutants, and the photolysis is its predominant degradation mechanism in the real environment. Currently the application of quantum chemical approaches to study the photolysis property has not reported. In this paper, the photo-degradability of all 135 iso-mers of was explored via computing heats of formation and energies of frontier molecular orbitals with AMI semiempirical computational method. The results indicated that the photolysis rates decrease with number of chlorine atoms in the molecular increase can be explained from the view of the heat of formation, while the reduction dechlorination becomes more predominant for the photolysis of PCDFs in water from the view of the energy of frontier molecular orbits, which have give a good theoretical explanation for the reported experimental results in the literatures.