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本文报道聚乙二醇(PEG)及其单醚类化合物在咪唑N-烷基化反应中的催化效应,它是以组成聚乙二醇的(CH_2CH_2O)单元中的氧同Im~-Na~+形成离子对参与反应的.催化剂活性与分子量关系不大,主要取决于分子链中有效的(CH_2CH_2O)单元个数,并以不少于5的单元个数组成配合基元通过界面传递阴离子.在一定的催化剂浓度下,遵循假一级反应动力学关系.由此求得的不同碳链(C_4～C_(16))烷基溴和咪唑发生N-烷基化反应的速度常数,显示碳链的空间结构对反应有明显的影响.咪唑和正-丁基溴发生N-正丁基化反应的活化能为12.4±0.5kcal/mol,还求取了该反应的活化参数△S、△H、△G,并与使用季铵盐和冠醚类化合物作相转移催化剂(PTC)的反应结果进行了对比.
In this paper, we report the catalytic effect of polyethylene glycol (PEG) and its monoethers on the N-alkylation of imidazole. It consists of the reaction of oxygen in the (CH 2 CH 2 O) + To form ion pair to participate in the reaction.The activity of the catalyst has little to do with the molecular weight, which depends on the number of CH 2 CH 2 O units in the chain, and the anions are transferred through the interface with the number of units of not less than 5. At a certain catalyst concentration, the pseudo first-order reaction kinetics was followed, and the rate constants of N-alkylation of different alkyl chains (C 4 -C 16) The spatial structure of the chain had a significant effect on the reaction.The activation energy of N-n-butylation reaction of imidazole and n-butyl bromide was 12.4 ± 0.5kcal / mol, and the activation parameters △ S and △ H , △ G, and compared with the reaction results using quaternary ammonium salts and crown ethers as the phase transfer catalyst (PTC).