【作者】 牛涛；

【导师】 宋启军；

【作者基本信息】 江南大学 ， 分析化学， 2008， 硕士

【摘要】 氯代酚作为常见的环境污染物,对其降解的研究已成为热点。本实验室在前期的研究中发现氯代酚敏化光降解的初级产物(中间体)遇氧化剂NBS,会有发光现象产生,且发光信号强度与氯代酚浓度密切相关,并由此建立了测定氯代酚的流动注射化学发光分析方法。同时实验研究已证实单线态氧与氯代酚反应直接导致了氯代酚的敏化光降解,但是目前我们无法通过实验手段来确定氯代酚敏化光降解后产生的中间体的结构,进而也无法深入探讨单线态氧参与下的氯代酚的敏化光降解机理。计算化学利用有效的数学近似以及电脑程序来计算分子性质进而研究化学问题。利用计算化学方法预测某些反应已取得很好的效果。为此,本文先后选择氯代酚中的代表物质2,4-二氯苯酚和邻氯苯酚作为模型分子,借助计算化学的方法从理论上来模拟单线态氧与氯代酚的反应,以期来推测出该类中间体的结构。依据Bobrowski等人提出的“单线态氧与芳香性和不饱和化合物加成时所涵盖的四大反应类型”,总结归纳出单线态氧与2,4-二氯苯酚(邻氯苯酚)反应的十二条具体的反应路径。通过密度泛函理论B3LYP方法在6-31+G(d, p)基组水平优化得到了反应路径上的反应物(反应复合物)、中间体、过渡态和产物的几何构型、零点能和谐振频率,同时在B3LYP/6-311+(2df, p)水平上进行了单点能计算。最后得出单线态氧与2,4-二氯苯酚(邻氯苯酚)的含有含氢基团的双键进行1,3加成反应,生成一个烯丙基氢过氧化物以及单线态氧与2,4-二氯苯酚(邻氯苯酚)进行1,4加成生成一个氢过氧化物酮类物质的反应,在热力学上发生的可能性较大;进而再通过对它们二者反应活化能垒的分析,发现单线态氧与2,4-二氯苯酚(邻氯苯酚)的含有含氢基团的双键进行1,3加成反应,生成一个烯丙基氢过氧化物的反应在动力学更可行。其间还通过反应过程中所涉及到的各驻点,对它们中的相关原子间的距离以及相关原子的NBO电荷的分析来揭示单线态氧与2,4-二氯苯酚(邻氯苯酚)反应的机理。更多还原

【Abstract】 Chlorophenols are frequently encountered organic pollutants in the environment. The study of its degradation has become a hot issue. In previous study, it was found in our laboratory that luminescence phenomenon can be produced when the photosensitized degradation products (light emitting precursors) of chlorophenols are treated with NBS. And there is a close correlation between chemiluminescence intensities and the concentrations of chlorophenols. Based on this principle, a series of flow injection chemiluminescence (FIA-CL) analytical methods for the determination of chlorophenols were established. It was generally recognized that the reaction between singlet oxygen and chlophenols is responsible to cause the photosensitized degradation of chlorophenols directly. But due to the complexity of the reaction matrix, the determination of the structures of the light emitting precursors by experimental means is often difficult. Hence it is also difficult to explain the reaction mechanism between singlet oxygen and chlorophenols. Computational chemistry methods are increasingly used for resolving chemistry problems by calculating the molecular properties with computer program. To better understand the chemical structures of the intermediate products formed in the photodegradation process, the reaction between singlet oxygen and chlorophenols is investigated with computational methods in this paper. 2, 4-dichlorophenol and o-chlorophenol were chosen as the model molecules for chlorophenols. Twelve reaction routes for the reaction between singlet oxygen and 2,4-dichlorophenol (o-chlorophenol) were induced by the four principal types of oxygen-addition reactions to aromatic and unsaturated compounds proposed by Bobrowski. The geometries of reactants (reactant complexes), intermediates, transition states and products were optimized at B3LYP/6-31+G (d, p) level. The corresponding vibration frequencies and zero-point energies were calculated at the same level. The single-point energies for all the stationary points were obtained at B3LYP/6-311+ (2df, p) level. We find that the reaction types of“1,3-addition to a double bond connected to a hydrogen-carrying group, resulting in the formation of allylic hydroperoxides”and“1,4-addition to chlorophenols with the formation of hydroperoxide ketones”have much probability than the other two reaction types. But the type of“1,3-addition to a double bond connected to a hydrogen-carrying group, resulting in the formation of allylic hydroperoxides”has the lowest reaction barriers, therefore is predicted to be the preferred route. We also analysis the distances between the correlation atoms and their NBO charges in order to study the reaction mechanism between 2, 4-dichlorophenol (o-chlorophenol) and singlet oxygen.更多还原