直链酸与水相互作用的理论研究

Theoretical study on the interaction of linear chain acid and water

采用量子化学方法中的密度泛函理论B3LYP方法,在B3LYP/6-311++G(d,p)基组水平上,对直链酸(甲酸至庚酸)与单分子水形成的体系进行结构优化和频率计算,从分子水平上研究了体系的相关的结构参数、电荷分布以及结合能,运用AIM理论分析了体系的电了密度拓扑。结果表明:直链酸与水形成两个氢键,其中羧基中氢原子作为质子供体的氢键1的键能强于水的氢作为质子供体的氢键2的键能。氢键1对体系的结合能影响起主导作用。稳定构型为六元环构型。直链酸与水结合能不随碳链增长呈明显变化,在(38.7-39.7)kJ/mol之间。

Based on B3LYP method in quantum chemistry methods, the optimized structure and frequency of the system of linear chain acid （methane acid to heptoic acid） and single-molecule water was calculated using the GAUSSIAN09 at B3LYP/6-311 ＋＋G （d, p） level. Quantum chemical simulation was used to study the structure changes, charge distribution, frequency changes and the binding energy. AIM theory wasused to study the electron density of the system topology. The results show that： all the systems form two hydrogen bonds, the hydrogen 1 （the hydrogen atom in the carboxyl group as a proton donor） is stronger than the hydrogen 2 （the hydrogen atom in water as a proton donor）. The hydrogen 1 plays a leading role of affecting the binding energy. Stable configuration for the system is a six-membered ring. The binding energy is in the range of （38.7-39.7） kJ/mol and it doesn＇t change a lot with the growth of the carbon.