Yamabe Shinichi, Tsuchida Noriko, Hayashida Yousuke
Department of Chemistry, Nara University of Education, Takabatake-cho, Nara 630-8528, Japan.
J Phys Chem A. 2005 Aug 18;109(32):7216-24. doi: 10.1021/jp058029i.
Density functional theory calculations were conducted on the title reactions with explicit inclusion of a variety of water molecules. Concerted reaction paths were examined first in the reaction model, ester(H2O)n --> MeCOOH(H2O)(n-1)EtOH, with n = 1-4. Their Gibbs activation energies are much larger than the experimental value, and the concerted paths are unfavorable. Various stepwise paths were investigated, and the ester(H2O)4 reactant gives a likely stepwise path. The n = 4 based reaction models, n = 4 + 5 and n = 4 + 12, were found to have similar proton-relay shapes with good hydrogen-bond directionality. The distinction of either the concerted or the stepwise path is described by the position of only one proton in the "junction" water molecule.
对标题反应进行了密度泛函理论计算，明确包含了各种水分子。首先在反应模型酯（H₂O）ₙ→MeCOOH（H₂O）ₙ₋₁EtOH（n = 1 - 4）中研究了协同反应路径。它们的吉布斯活化能远大于实验值，且协同路径不利。研究了各种分步路径，酯（H₂O）₄反应物给出了一条可能的分步路径。发现基于n = 4的反应模型n = 4 + 5和n = 4 + 12具有相似的质子传递形状和良好的氢键方向性。协同路径或分步路径的区别仅由“连接”水分子中一个质子的位置来描述。
