2-氨基乙醇振动频率及碱度的理论研究

Theoretical Studies on the Vibration Frequencies and Basicities of 2-aminoethanol

运用B3LYP方法在6-311+G(d,p)水平上对气相、水及四氯化碳溶液中2-氨基乙醇的构型稳定性、分子内氢键强度、振动频率及气相碱度进行了研究。计算结果表明,在气相中g′Gg′构型因具有分子内氢键而成为最稳定的构型。水溶液中2-氨基乙醇构型的稳定性决定于分子内氢键和羟基基团分子间溶剂化的综合作用。通过对振动模式的分析,表明随着构型能量的增加,各构型中C-O-H键弯曲和C-O键振动频率均蓝移,而O-H键振动频率红移;四氯化碳溶液中的振动频率和实验结果一致,计算结果表明G型2-氨基乙醇的气相碱度比T型的大。

The conformational stability,intramolecular H-bond strength,energy barriers,vibrational frequencies and gas-phase basicities of nine most stable conformers of 2-aminoethanol in gas phase and in aqueous and carbon tetrachloride solutions have been investigated at B3LYP level with 6-311＋G（d,p） basis set.In gas phase,the results suggest that the conformer g′Gg′,which exhibits an intramolecular H-bond of type–OH…N,is the most stable conformer.In aqueous solution,the calculations indicate that the stabilizations of 2-aminoethanol conformations are determined by the combination of intramolecular hydrogen bonds and intermolecular solvation of hydroxyl groups.The normal mode analysis for vibrational frequencies shows that the C-O-H bending and the C-O stretching frequencies of the conformers from high energy to low energy are blue-shifted,the O-H stretching frequency is red-shifted conversely.The computed vibrational frequencies in carbon tetrachloride solution are in agreement with the experimental data well.The calculated results of gas-phase basicities of different 2-aminoethanol conformers suggest that the Gas-phase basicities（GBs） of G-type conformers are higher than that of T-type conformers.