摘要
甲硫嘧磺隆,试验代号为HNPC-C9908,化学名称为2-(4-甲氧基-6-甲硫基嘧啶-2-基)氨基甲酰基氨基磺酰基苯甲酸甲酯,是我国具有自主知识产权的新型磺酰脲类除草剂,主要用于麦田杂草的防除。采用HPLC和LC/MS研究了甲硫嘧磺隆的醇解动力学及其机理。结果表明,甲硫嘧磺隆在甲醇和乙醇中可发生快速的醇解反应,并可用一级动力学方程很好描述,其醇解半衰期分别为10.6和11.6d,说明醇解反应可能是磺酰脲类化合物的普遍特征之一。甲硫嘧磺隆的醇解反应因温度、pH值、甲醇含量以及有效成分浓度而异。甲硫嘧磺隆的醇解速率随温度升高而加快,其在15、25、35和45℃等4个温度下的醇解半衰期分别为41.0d、10.6d、3.8d和13.0h,温度效应系数为28.06;甲硫嘧磺隆醇解反应的活化能和活化焓与温度之间无明显相关性,其平均活化能和活化焓分别为186.28和183.71kJ·mol-1,而活化熵绝对值则随温度升高而增加,表现出良好的相关性,其平均活化熵为-11.28kJ·mol-1·K-1,说明甲硫嘧磺隆的醇解主要为双分子亲核取代反应;甲硫嘧磺隆在酸性醇液中的降解速率明显快于中性和碱性醇溶液中的降解速率,其在pH5、7和9的甲醇液中的醇解半衰期分别为6.8、172.2和109.5d;当甲醇含量为40%、50%、60%、70%、80%、90%和100%时,甲硫嘧磺隆的降解半衰期为27.8、30.7、30.1、43.3、42.5、43.9和10.6d,而在纯水中的半衰期为29.4d;在浓度较低(5mg·L-1)时,甲硫嘧磺隆的醇解速率较慢,其醇解半衰期为32.2d,而当增加到10和20mg·L-1时,对甲硫嘧磺隆的醇解速率影响不大。甲硫嘧磺隆醇解的主要途径是分子中脲桥裂解生成2-苯甲酸甲酯基磺酰基氨基甲酸酯和2-氨基-4-甲氧基-6-甲硫基嘧啶。
Methiopyrisulfuron （ test code ： HNPC -C9908 ）, methyl 2-[（4-methoxy-6 -methyhhio -pyrimidin -2-yl）carbamoylsulfamoyl] benzoate, is a novel sulfonylurea herbicide developed by Hunan Research Institute of Chemical Industry that has been used for weed control in wheat. The alcoholysis kinetics and its mechanisms of methiopyrisulfuron were studied using high performance liquid chromatography and mass spectra. Results showed that the rapid aleoholysis of herbicide methiopyrisulfuron occurred in methanol or ethanol, and the reaction rates could be described satisfactorily with the first-order kinetics equation. The calculated half-life of methiopyrisulfuron in methanol and ethanol was 10.6 days and 11.6 days, respectively, implying that the alcoholysis reaction appears to be a general characteristic of sulfonylurea herbicides. Alcholysis of methiopyrisulfuron varied with the temperatures, pH value, methanol content and active ingredient concentrations. Alcoholysis reaction rate of methiopyrisulfuron increased as the incubation temperature went up, and its half-life was 41.0 d, 10.6 d, 3.8 d and 13.0 b, respectively, at 15 ℃, 25℃, 35 ℃ and 45 ℃, and the temperature coefficient of methiopyrisulfuron aleoholysis was 28.06. There existed no obvious correlations between the activation energies of methiopyrisulfuron alcoholysis and temperatures, and its average activation energy and activation enthalpy was 186.28 kJ. mol^-1 and 183.71 kJ. mol^-1, respectively. The activation entropy absolute values of methiopyrisulfuron aleoholysis increased with the increasing temperatures in the environment, and its average activation entropy value was -11.28kJ. mol^-1· K^-1, indicating that alcoholysis of methiopyrisulfuron proceeds via a nucleophilic substitution mechanism. Alcoholysis rates of me-thiopyrisulfuron was significantly higher in acidic methanol solution than neutral and basic methanol solution, and its half-life in the methanol solution of pH5, 7 and 9 was 6.8 d, 172.2 d and 109.5 d, respectively. The hal
出处
《农业环境科学学报》
CAS
CSCD
北大核心
2010年第2期368-374,共7页
Journal of Agro-Environment Science
基金
国家十一五科技支撑计划课题(2006BAE01A04)
国家自然科学基金项目(20872033)
湖南省自然科学基金项目(09JJ3015)
