Intramolecular hydrogen bonding, gauche interactions, and thermodynamic functions of 1,2-ethanediamine, 1,2-ethanediol, and 2-aminoethanol: A global conformational analysis
Intramolecular hydrogen bonding, gauche interactions, and thermodynamic functions of 1,2-ethanediamine, 1,2-ethanediol, and 2-aminoethanol: A global conformational analysis
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DOI：
10.1021/jp971022j
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发表时间：
1997-08-21
影响因子：
2.9
通讯作者：
Chao, I
中科院分区：
文献类型：
--
作者：
Chang, YP;Su, TM;Chao, I
1,2-乙二醇、1,2-乙二胺和2-氨基乙醇（X- ch2 - ch2 -Y； X, Y = OH或NH2）的整体构象势在MP2/6-311+G（2d,p）水平上通过扫描两个官能团和碳-碳键的二面角得到，其余核坐标能量最小。发现电位可以用相邻分子片段之间的直接键电位和相邻分子片段和相邻分子片段之间的穿越空间静电电位来表示。在这里，通过-直接键势用常规的三个傅里叶项表示，通过空间势，包括X和Y之间的分子内氢键，用电偶极-偶极、偶极-四极和四极-四极相互作用项的一般功能形式表示。拟合的X和Y片段之间的静电相互作用强度与Hirshfeld电荷居群分析计算的分子片段偶极矩和四极矩的理论预测相吻合。在此能量分解方案下，可以得到不受分子内氢键影响的内征间扭相互作用，并将其与X和y的基团电负性相关联。利用整体构象势，计算了分子及其单个构象的热力学函数，并与文献中气相实验热力学数据进行了比较。
The global conformational potentials of 1,2-ethanediol, I,2-ethanediamine, and 2-aminoethanol (X-CH2-CH2-Y; X, Y = OH or NH2) were obtained at the MP2/6-311+G(2d,p) level by scanning through the dihedral angles of the two functional groups and the carbon-carbon bond with the remaining nuclear coordinates being energy-minimized. It was found that the potentials could be represented by the direct-bond potentials between the adjacent molecular fragments and by the through-space electrostatic potentials between the vicinal and geminal fragments. Here, the through-direct-bond potentials are represented by the conventional three Fourier terms of the internal rotation angles, and the through-space potentials, which include the intramolecular hydrogen bonding between X and Y, are represented by the general functional forms of the electric dipole-dipole, dipole-quadrupole, and quadrupole-quadrupole interaction terms. The fitted electrostatic interaction strengths between the X and Y fragments are in good agreement with the predictions of the theoretical molecular fragment dipole and quadrupole moments calculated by the Hirshfeld charge population analysis. Under the present energy decomposition scheme, the intrinsic gauche interactions, which are free of the contribution of the intramolecular H-bonding, could be obtained and correlated with the group electronegativities of X and Y. The potentials were also calculated by the MM3 molecular mechanics method and compared with the present results. With the global conformation potentials, the thermodynamic functions of the molecules and also their individual conformers are calculated and compared with the gas-phase experimental thermodynamic data in the literature.