苏氨酸对甲苯磺酸盐及其酯化物的微波合成、表征及量化计算

以苏氨酸(Thr)和对甲苯磺酸(p-TsOH)为原料, 用一步法在微波反应仪中合成了离子液体苏氨酸对甲苯磺酸盐(Thr-TsOH), 并采用对甲苯磺酸法一步制得其甲酯和乙酯化合物ThrC1-TsOH和ThrC2-TsOH. 对合成的离子液体的理化性质进行了表征, 它们均具有较低的熔点(低于100 ℃), 但热稳定性相对较差. 结合量化计算理论方法初步探索了氨基酸酯化对熔点的影响. 采用DFT的B3LYP/6-311++G**方法对苏氨酸对甲苯磺酸及其甲酯、乙酯化合物3种分子进行构型优化及振动频率分析, 通过对分子中阴、阳离子间结合能的研究发现, 酯化不仅能减弱分子间氢键相互作用, 还能明显减弱分子内离子间相互作用, 从而降低体系的熔点.

Microwave Synthesis, Characterization and Theoretical Study of para Toluenesulfonic Acid Threomine Salt and Its Ester Derivatives

Some newamino acid ionic liquids (ILs) derivedfromthreonine (Thr)were studied. The para-toluenesulfonic acid threonine and its methyl ester (ThrC1-TsOH) and ethyl ester (ThrC2-TsOH) derivatives were synthesized with one-step microwave synthesis method, and their physicochemical properties, including the IR spectra, melting points, and thermostability, were studied experimentally. Quantum chemistry calculations were also performed to study the influence of the esterification of cation on the melting point. Geometry optimizations on the single molecules of the Thr complex and its methyl and ethyl ester complexes in gas phase were performed with DFT B3LYP/6-311++G** method, and the vibration frequencies of each optimized molecule were analyzed at the same level method. The binding energies between ions were calculated and the basis set superposition error (BSSE) was corrected with counterpoise method (CP). It was found that the esterification of cation would weaken not only the intermolecular hydrogen bond interaction, but also the intramolecular interaction between ions obviously. And so the decrease of the melting point is caused by the two factors, and the weakenness of intramolecular interaction should be the main factor for the titled compound to be an ionic liquid.