在常压釜式反应器中,以乙酸为溶剂,开展了乙酸铵(氨源)与甲醛、乙醛和丙烯醛中的一种或多种反应制备吡啶碱的研究。通过Hückel和Mulliken模型的量子化学和热力学计算,分析了丙烯醛和反应中间体丙烯亚胺的构型和电荷,考察了生成中间体二氢吡啶和产物3-甲基吡啶过程中的静电相互作用、前线分子轨道和能量变化,从而提出了丙烯醛/氨合成3-甲基吡啶的反应机理,并总结了醛/氨反应制吡啶碱反应的一般规律。理论预测的产物组成与实验结果具有良好的一致性。
Pyridine bases were prepared by reactions of aldehydes(formaldehyde,acrolein and/or acetaldehyde)with ammonium acetate,using acetic acid as solvent,in a refluxing tank reactor under atmospheric pressure.Quantum chemical and thermodynamic calculations were conducted to analyze the configurations and charges of acrolein and propylene imine and to investigate the electrostatic interaction,frontier molecular orbital and energy changes during the formations of intermediate dihydropyridine and product 3-methyl pyridine.Based on these results,a reaction mechanism was proposed for the formation of 3-methyl pyridine from acrolein and ammonia,and also,a general rule was summarized for the reaction of aldehyde with ammonia to form pyridine bases.The products distribution predicted theoretically was consistent with that obtained by experiment.