C6H5NH-H□X分子间氢键的理论研究

摘要

The geometric structures optimization and vibration frequency calculation on a series of C6H5 NH - H□X hydrogen - bonded complexes involving H2O, HCOH, NH3 , CH3 COCH3, CH2NH and HCN as proton acceptors were performed at B3LYP/6 -311 ＋ ＋ G（3df,2p） level. Natural bond orbital analysis and thermodynamic property studies were performed on the stable structures. The resuits show that a strong N -H□O and N -H□N hydrogen- bond exists in C6H5NH -H□X hydrogen- bonded complexes. The formation of hydrogen bond forces the vibration frequency of H - N red - shift apparently. At 298.15 K and standard state, the formations of C6H5NH- H□X system molecular are exothermic, entropy decreasing and non -spontaneous processes in the gaseous phase.%在B3LYP／6-311＋＋G（3df，2p）理论水平上，对C6H5NH-H□X（X=H2O，HCOH，CH3COCH3，NH3，CH2NH和HCN）氢键体系进行几何结构优化与振动频率计算，在所得稳定构型的基础上进行自然键轨道分析和热力学性质研究．结果表明，C6H5NH-H□X体系存在较弱的N—H□O与N—H□N氢键，氢键的形成使H—N伸缩振动频率明显红移．在298．15K和标准状态下，C6H5NH-H□X体系分子在气相的形成过程是一个放热、熵减的非自发过程．