Dorofeeva Olga V, Vogt Natalja, Vogt Jürgen, Popik Mikhail V, Rykov Anatolii N, Vilkov Lev V
Department of Chemistry, Moscow State University, Moscow 119992, Russia.
J Phys Chem A. 2007 Jul 19;111(28):6434-42. doi: 10.1021/jp072122k. Epub 2007 Jun 27.
The molecular structure of 1,3-dihydroxyacetone (DHA) has been studied by gas-phase electron diffraction (GED), combined analysis of GED and microwave (MW) data, ab initio, and density functional theory calculations. The equilibrium re structure of DHA was determined by a joint analysis of the GED data and rotational constants taken from the literature. The anharmonic vibrational corrections to the internuclear distances (re-ra) and to the rotational constants (B(i)e-B(i)0) needed for the estimation of the re structure were calculated from the B3LYP/cc-pVTZ cubic force field. It was found that the experimental data are well reproduced by assuming that DHA consists of a mixture of three conformers. The most stable conformer of C2v symmetry has two hydrogen bonds, whereas the next two lowest energy conformers (Cs and C1 symmetry) have one hydrogen bond and their abundance is about 30% in total. A combined analysis of GED and MW data led to the following equilibrium structural parameters (re) of the most abundant conformer of DHA (the uncertainties in parentheses are 3 times the standard deviations): r(C=O)=1.215(2) A, r(C-C)=1.516(2) A, r(C-O)=1.393(2) A, r(C-H)=1.096(4) A, r(O-H)=0.967(4) A, angleC-C=O=119.9(2) degrees, angleC-C-O=111.0(2) degrees, angleC-C-H=108.2(7) degrees, angleC-O-H=106.5(7) degrees. These structural parameters reproduce the experimental B(i)0 values within 0.05 MHz. The experimental structural parameters are in good agreement with those obtained from theoretical calculations. Ideal gas thermodynamic functions (S degrees (T), C degrees p(T), and H degrees (T)-H degrees (0)) of DHA were calculated on the basis of experimental and theoretical molecular parameters obtained in this work. The enthalpy of formation of DHA, -523+/-4 kJ/mol, was calculated by the atomization procedure using the G3X method.
通过气相电子衍射（GED）、GED与微波（MW）数据的联合分析、从头算以及密度泛函理论计算，对1,3 - 二羟基丙酮（DHA）的分子结构进行了研究。通过对GED数据和文献中获取的转动常数进行联合分析，确定了DHA的平衡再结构。利用B3LYP/cc - pVTZ立方力场计算了估计再结构所需的核间距（$r_e - r_a$）和转动常数（$B_i^e - B_i^0$）的非谐振动校正。结果发现，假设DHA由三种构象异构体的混合物组成时，实验数据能够得到很好的再现。对称性为$C_{2v}$的最稳定构象异构体有两个氢键，而接下来两个能量最低的构象异构体（$C_s$和$C_1$对称性）有一个氢键，它们的总丰度约为30%。GED和MW数据的联合分析得出了DHA最丰富构象异构体的以下平衡结构参数（括号内的不确定度为标准偏差的3倍）：$r(C = O)=1.215(2)\mathring{A}$，$r(C - C)=1.516(2)\mathring{A}$，$r(C - O)=1.393(2)\mathring{A}$，$r(C - H)=1.096(4)\mathring{A}$，$r(O - H)=0.967(4)\mathring{A}$，$\angle C - C = O = 119.9(2)^{\circ}$，$\angle C - C - O = 111.0(2)^{\circ}$，$\angle C - C - H = 108.2(7)^{\circ}$，$\angle C - O - H = 106.5(7)^{\circ}$。这些结构参数在0.05 MHz范围内再现了实验$B_i^0$值。实验结构参数与理论计算得到的参数吻合良好。基于本工作中获得的实验和理论分子参数，计算了DHA的理想气体热力学函数（$S^{\circ}(T)$、$C_p^{\circ}(T)$和$H^{\circ}(T)-H^{\circ}(0)$）。采用G3X方法通过原子化程序计算得出DHA的生成焓为$-523 \pm 4$ kJ/mol。
