2-氯-5-三氯甲基吡啶电化学脱氯合成2-氯-5-氯甲基吡啶

Electrochemical dechlorination of 2-chloro-5-trichloromethylpy to 2-chloro-5-chloromethylpridine

摘要:

2-氯-5-三氯甲基吡啶（TCMP）电化学脱氯合成2-氯-5-氯甲基吡啶（CCMP）在农药“吡虫啉”合成中具有重要工业应用价值。本文采用电解合成法研究了支持电解质、阴极材料及目数、反应温度和电流密度等工艺条件对上述反应的影响和TCMP及其脱氯中间产物的脱氯电位。实验结果表明：在乙酸锂、氯化锂、高氯酸锂、氯化铵、四丁基高氯酸铵中，乙酸锂为最佳支持电解质。各阴极材料上CCMP收率从高到低次序为：铜＞铅＞石墨＞银＞锌＞镍。在优化条件下（阴极液：含10 φ(%)乙酸 5 φ(%)水 0.2 mol/L乙酸锂 0.1 mol/L TCMP的甲醇溶液；阴极：80目铜网；反应温度：30℃；电流密度：前期电流密度为333 A/m2，后期为166 A/m2），0.1 mol/L TCMP能较高效地转化为CCMP，其收率可达56.9%。TCMP脱氯成2-氯-5-二氯甲基吡啶（DCMP）的电位明显正于DCMP脱氯成CCMP的脱氯电位，后者与CCMP进一步脱氯的电位则非常接近。

Abstract:

Electrochemical dechlorination of 2-chloro-5-trichloromethylpyridine (TCMP) to 2-chloro-5-chloromethylpyridine (CCMP) has important industrial application value in the preparation of imidacloprid. In this work, the influence of various process conditions (such as supporting electrolyte, cathode materials and their mesh number, temperature and current density) on the dechlorination, and the dechlorination potentials of TCMP and its dechlorinated products were investigated using bulk electrolysis experiments. The experimental results show that lithium acetate is the best choice among lithium acetate, lithium chloride, lithium perchlorate, ammonium chloride and tetrabutyl ammonium perchlorate. The yield of CCMP on each cathode material decreases in the following order: Cu > Pb > graphite > Ag > Zn > Ni. Under optimized process conditions (catholyte: methanol solution containing 10 φ(%) CH3COOH 5 φ(%) H2O 0.2 mol/L CH3COOLi 0.1 mol/L TCMP, cathode: 80 mesh copper, temperature: 30℃, the current density: 333 A/m2 at the early stage of reaction and 166 A/m2 at the last stage of reaction), 0.1 mol/L TCMP could be selectively dechlorinated to CCMP with the yield of 56.9%. The dechlorination po-tential of TCMP to DCMP is more positive than that of DCMP to CCMP, and the later is almost same to that of CCMP to CMP.