摘要
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%。
ω-Monobromination of 2,4-dichloroacetophenone and the factors influencing the yield of ω-bromo-2,4-dichloroacetophenone(namely monobromide) were studied. It was proved that when taking benzene,dichloromethane,carbon tetrachloride or 1,2-dichloroethane as reaction medium,the yields of monobromide were between 84% and 86%;when taking ether,chloroform,methanol,ethanol or acetic acid as reaction medium,the yields were only 69% to 77%,but increasing the use level of bromine in solvent methanol,ethanol or chloroform can raise the yields,for example,to 89.23% in ethanol.Increasing the amount of solvent used or washing the product solution with water or base before evaporating didn' t change the yield of monobromide.In reaction medium benzene,the reaction temperature at -10 ℃ to 10 ℃ didn' t affect the monobromination,but heating was necessary when some water was added in,and the monobromide yield was decreased.Heating was necessary too,when 1,2-dichloroethane,methanol or ethanol was used,or bromine-dioxane complex was taken as brominating agent.The bromine-dioxane complex can not reduce the by-product ω,ω-dibromo-2,4-dichloroacetophenone.By blowing nitrogen to remove HBr or absorbing HBr with H_2O_2 during the reaction,yield of target compound can be raised to 89.40% or 89.74% respectively.
出处
《精细化工》
EI
CAS
CSCD
北大核心
2004年第2期153-156,共4页
Fine Chemicals
