[BPy]Br和[BMIm]Br微波辅助合成动力学

Reaction kinetics of [BPy] Br and [BMIm] Br under microwave-assisted synthesis

在微波反应仪中,于微波辐照下分别由吡啶、N-甲基咪唑与溴代正丁烷合成了溴化N-丁基吡啶（[BPy]Br）及溴化1-甲基-3-丁基咪唑（[BMIm]Br）,利用AgNO3电位滴定法测定了动力学数据,建立了动力学方程,研究了反应物、温度、溶剂对反应动力学的影响,并对微波作用机制进行了探讨。结果表明：反应遵循SN2历程,总包反应级数为二级;反应速率常数较传统加热方法提高近10倍,且随温度升高而增大;在异丙醇中合成[BPy]Br比在正庚烷中的速率常数值约高5倍;合成[BMIm]Br的活化能为30.39 kJ/mol,合成[BPy]Br的活化能为92.17~97.27 kJ/mol。与传统加热方法的动力学数据相比,微波作用不改变反应历程和活化能,但通过提高反应频率因子的方式能显著加快反应速率。

N-methyl imidazole bromide（[BPy]Br） and 1-methyl-3-butyl imidazole bromide（[BMIm]Br） were synthesized by the respective reactions of pyridine and N-methyl imidazole under microwave radiation in a microwave reactor.Reaction kinetics was determined by AgNO3 titration to obtain the reaction kinetics equation,and the influences of reactants,temperature,and solvent were also investigated.The mechanism of microwave-assisted reactions was proposed.Results showed that the reaction abides by SN2 mechanism,and the global reaction was of the second order.The reaction rate constant was enlarged by 10 times compared to traditional heating methods,and increased with rising temperaturing.The rate constant for synthesis of [BPy]Br in isopropanol was about 5 times larger than in n-heptane.The activation energy was 30.39kJ/mol for synthesis of [BMIm]Br,and 92.17～97.27kJ/mol for synthesis of Br.Microwave radiation could take effect by increasing reaction frequency factors instead of changing the reaction mechanism and activation energy.