Surface photochemistry of pesticides containing 4-chlorophenoxyl chromophore
Surface photochemistry of pesticides containing 4-chlorophenoxyl chromophore
复制标题
DOI：
10.1016/j.jhazmat.2010.02.077
复制
发表时间：
2010-07-15
影响因子：
13.6
通讯作者：
Machado, Isabel Ferreira
中科院分区：
文献类型：
--
作者：
Da Silva, Jose P.;Vieira Ferreira, Luis F.;Machado, Isabel Ferreira
用漫反射和层析技术研究了含4-氯苯氧基发色团的农药在模型表面纤维素和二氧化硅上的表面光化学行为。以4-氯苯甲醚为模型化合物，在紫外灯(254 Nm)和太阳光照射下对其进行光转化。纤维素的光降解速率快于二氧化硅。纤维素的主要光降解产物为苯甲醚和二聚化合物，而在二氧化硅上的主要反应途径为4-羟基苯甲醚的生成和二聚反应。瞬时吸收研究表明，只有在氧气存在的情况下，4-甲氧基苯基过氧基才会在纤维素上形成。C-Cl键的均质裂解和随后形成的三重自由基对是两个表面上的主要反应步骤。然后，自由基对扩散或进行电子转移，分别形成苯基和苯基阳离子。这两种反应的中间产物导致了键合残留物的还原、加成和形成，这是在所研究的表面上观察到的主要反应，也有望在自然条件下占优势。(C)2010爱思唯尔B.V.保留所有权利。
The surface photochemistry of pesticides containing 4-chlorophenoxyl chromophore was accessed on the model surfaces cellulose and silica, using diffuse reflectance and chromatographic techniques. 4-Chloroanisole was chosen as the model compound and its phototransformation was followed under lamp (254 nm) and sunlight irradiation. The photodegradation rates are faster on cellulose than on silica. The main photodegradation products on cellulose are anisole and dimerization compounds while on silica the formation of 4-hydroxyanisole and dimerization are the main reaction pathways. Transient absorption studies showed the formation of the 4-methoxyphenylperoxyl radical only on cellulose and in the presence of oxygen. The homolytic cleavage of the C-Cl bond, and consequent formation of a triplet radical pair, is the main primary reaction step on both surfaces. The radical pair then diffuses apart or undergoes electron transfer to form phenyl radicals and phenyl cations, respectively. These two reaction intermediates account for reduction, addition, and formation of bonded residues, the main reactions observed on the studied surfaces and also expected to prevail under natural conditions. (c) 2010 Elsevier B.V. All rights reserved.