Hori Takumi, Takahashi Hideaki, Furukawa Shin-Ichi, Nakano Masayoshi, Yang Weitao
Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Machikaneyama-cho 1-3, Toyonaka, Osaka 560-8531, Japan.
J Phys Chem B. 2007 Jan 25;111(3):581-8. doi: 10.1021/jp066334d.
We have applied the quantum mechanical/molecular mechanical (QM/MM) method combined with the theory of energy representation (ER) to study the acidity of acetic acid in aqueous solution. We have focused our attention on the relative acidity DeltapK(a) of the molecule with respect to water solvent to circumvent the ambiguity of the solvation free energies of the molecular species referred to as proton. The value of DeltapK(a) for the acetic acid has been computed as -11.5 when we adopt the free energy change in the gas phase obtained by the B3LYP functional, which is in excellent agreement with the experimental value of -11.0. It has been demonstrated that the QM/MM-ER approach recently developed gives an adequate description for the solvation free energies related to the acidity/basicity calculations of organic molecules.
我们应用量子力学/分子力学（QM/MM）方法并结合能量表示理论（ER）来研究水溶液中乙酸的酸度。我们将注意力集中在分子相对于水溶剂的相对酸度ΔpK(a)上，以规避被称为质子的分子物种的溶剂化自由能的模糊性。当我们采用由B3LYP泛函得到的气相自由能变化时，计算出的乙酸的ΔpK(a)值为 -11.5，这与 -11.0的实验值非常吻合。结果表明，最近开发的QM/MM-ER方法能够对与有机分子酸度/碱度计算相关的溶剂化自由能给出充分的描述。
