离子液体催化氯乙酸甲酯合成氯乙酸-2-庚酯的研究

Study on the synthesis of 2-heptyl chloroacetate from methyl chloroacetate by using ionic liquid as a catalyst

探索了离子液体催化氯乙酸甲酯和2-庚醇的酯交换反应,制备了1-甲基-3-(丙基-3-磺酸基)咪唑对甲苯磺酸盐[MIM-PS][PTSA]、1-甲基-3-(丙基-3-磺酸基)咪唑硫酸氢盐[MIM-PS][HSO_(4)]、1-丁基-3-甲基咪唑硫酸氢盐[BMIM]HSO_(4)、N-甲基咪唑磷酸盐[HMIM]H_(2)PO_(4)四种离子液体催化剂并用于酯交换反应,通过考察产品氯乙酸-2-庚酯收率,筛选出最佳催化剂[MIM-PS][PTSA]。并用[MIM-PS][PTSA]考察了反应温度、反应时间、催化剂添加量、催化剂循环使用对合成产品收率的影响。结果表明:将氯乙酸甲酯和2-庚醇在100℃下,添加5%[MIM-PS][PTSA]催化剂,反应6 h,合成氯乙酸-2-庚酯,收率可达76.3%,离子液体重复使用3次,氯乙酸-2-庚酯收率仍大于初次收率的95%。本实验用离子液体做溶剂或催化剂,反应条件稳定,可循环利用、对环境友好,且产品收率高,为工艺放大提供实验条件参考。

2-Heptyl chloroacetate is an important intermediate for synthesizing new pesticides and herbicides.Conventional esterification reactions often use traditional strong acids,which is harmful to equipment and shows low product yield.Using ionic liquids as solvents or catalysts can make the reaction conditions stable,recyclable and environment-friendly,and lead to high product yield.Herein,the transesterification reaction between methyl chloroacetate and 2-heptanol was studied.Four ionic liquid catalysts were synthesized,including 1-methyl-3-(propyl-3-sulfonic acid)imidazole p-toluenesulfonic acid salt[MIM-PS][PTSA],1-butyl-3-methylimidazole hydrosulfate[BMIM]HSO_(4),1-methyl-3-(propyl-3-sulfonic acid)imidazole hydrosulfate[MIM-PS][HSO_(4)]and N-methylimidazole phosphoric acid salt[HMIM]H_(2)PO_(4).These four ionic liquid catalysts were used in a transesterification reaction.According to the product yield of the transesterification reaction,the optimal catalyst[MIM-PS][PTSA]was screened.The effects of ester-alcohol ratio,reaction temperature,reaction time,catalyst dosage and catalyst cycle were investigated in the presence of[MIM-PS][PTSA].The results showed that,for the reaction between methyl chloroacetate and 2-heptanol,5%[MIM-PS][PTSA]catalyst was added,the reaction temperature was 100℃,and the reaction time was 6 h,indicative of a yield of 76.3%.When the ionic liquid was reused for three times,the yield of 2-heptyl chloroacetate was still greater than the 95%of the initial yield.When the catalyst was more than 5%or the temperature was too high,byproducts such as 2-heptene or 2-heptyl ether might be formed.When the reaction time was too long,the product might undergo substitution reaction to form corresponding ether compounds.In this work,ionic liquids were used as solvents or catalysts,and the reaction conditions were stable,recyclable and environment-friendly,and the product yield was high,which could provide reference for the conditions of process amplification.