相转移法合成2,4-二羟基二苯甲酮

间苯二酚水溶液与三氯甲苯反应可制备紫外线吸收剂 2 ,4-二羟基二苯甲酮。通过向反应体系中加入少量水溶性的有机溶剂可明显改善产品质量。实验结果表明 ,二甲基甲酰胺和冰醋酸的效果较好。重点考察了各类表面活性剂对该反应的影响。这些表面活性剂包括十八烷基二甲基苄基氯化铵、十六烷基三甲基溴化铵、四丁基溴化铵、十二烷基磺酸钠、十二烷基硫酸钠、工业乳化剂和聚乙二醇等。实验发现十六烷基三甲基溴化铵的用量为 0 .8% (基于水的质量分数 )时 ,2 ,4-二羟基二苯甲酮的纯度可达 99.7% ,产品的分离产率为 95 .7% ,外观为淡黄色 ,十六烷基三甲基溴化铵是一种比较理想的相转移催化剂

A Phase Transfer Method for the Synthesis of 2,4-Dihydroxybenzophenone

Dihydroxybenzophenone can be prepared by reacting of resorcinol with benzotrichloride in water. The quality of product is improved significantly by adding some water-soluble organic solvent into the reaction system. It is demonstrated that acetic acid and dimethylformamide give better results. The influences of various surfactants on this reaction are mainly investigated. These surfactants are octadecyldimethylbenzylammonium chloride, octadecyltrimethylammonium bromide, tetrabutylammonium bromide, 1-Dodecane sulfonic acid sodium salt, sodium dodecyl sulfate, some industrial pure emulsifiers and polyethylene glycol (PEG). It is found that the purity and yield of 2,4-Dihydroxybenzophenone reaches 99.7% and 95.7% respectively by adding 0.8% octadecyltrimethylammonium bromide (by weight of water) into the reaction mixture. Octadecyltrimethylammonium bromide is an ideal phase transfer catalyst.