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研究了2,4 二氯苯乙酮ω 位单溴化反应及其影响ω 溴 2,4 二氯苯乙酮(即单溴物)收率的各种因素。结果表明,以苯、二氯甲烷、四氯化碳与1,2 二氯乙烷等作为反应介质时,单溴物的收率为84%～86%,而以乙醚、三氯甲烷、甲醇、乙醇及冰醋酸等作为反应介质,单溴物的收率只有69%～77%,但在甲醇、乙醇或三氯甲烷等溶剂中,增加溴的用量收率增加,如在乙醇中收率可升至89 23%。脱去溶剂前是否用水或碱溶液洗涤,对单溴物的收率没有明显影响。以苯为反应介质时,温度在-10～10℃对单溴化的影响不大,但在加入水时,收率下降,且需要加热反应才能正常进行。在1,2 二氯乙烷、甲醇、乙醇等溶剂中,或以络合态溴作为溴化剂时,反应也需要加热。溴与二氧六环形成络合物后,不能减少ω,ω 二溴 2,4 二氯苯乙酮(即二溴物)的产生。反应过程中吹入N2排除HBr,或用H2O2吸收并利用HBr,可使单溴物收率分别上升到89 40%和89 74%。
The monobromination reaction of 2,4-dichloroacetophenone and its effect on the yield of ω-bromo-2,4-dichloroacetophenone (ie, monobromobenzene) were studied. The results showed that the yield of monochromate was 84% ~ 86% with benzene, dichloromethane, carbon tetrachloride and 1,2-dichloroethane as the reaction medium. The yield of monobromide was 84% ~ 86% , Ethanol and glacial acetic acid as the reaction medium, the yield of monochromate is only 69% ~ 77%, but in the solvent of methanol, ethanol or trichloromethane, the dosage of bromine increased, such as the yield of ethanol Can rise to 89 23%. Whether or not the solvent was washed with water or an alkali solution before removal of the solvent had no significant effect on the yield of the monobromide product. With benzene as the reaction medium, the temperature of -10 ~ 10 ℃ on the single bromine little effect, but when adding water, the yield decreased, and the need for heating reaction to normal. The reaction also requires heating in solvents such as 1,2-dichloroethane, methanol, ethanol and the like, or with complexed bromine as the brominating agent. The formation of complexes of bromine with dioxane can not reduce the production of ω, ω dibromo-2,4-dichloroacetophenone (ie dibromo). During the reaction, N2 was blown in to remove HBr, or H2O2 was absorbed and HBr was used to increase the yield of monobromide to 89 40% and 89 74%, respectively.