Krizner Hadley E, De Haan David O, Kua Jeremy
Department of Chemistry, University of San Diego, 5998 Alcala Park, San Diego, California 92110, USA.
J Phys Chem A. 2009 Jun 25;113(25):6994-7001. doi: 10.1021/jp903213k.
Density functional theory (B3LYP//6-311+G*) calculations, including Poisson-Boltzmann implicit solvent and free energy corrections, are applied to study the hydration of methylglyoxal and the subsequent formation of dimeric species in solution. Our calculations show that, unlike glyoxal, fully hydrated species are not thermodynamically favored over their less hydrated counterparts, nor are dioxolane ring species the thermodynamic sink, which is in agreement with experimental data. Instead, we find that aldol condensations are the most favored oligomerization reactions for methylglyoxal. These results differ from those of glyoxal, which, lacking the methyl group, cannot access the enol structure leading to aldol condensation. For methylglyoxal, the product from nucleophilic attack at the aldehyde rather than the ketone was favored. Our results help explain some of the observed differences between methylglyoxal and glyoxal, in particular the different array of oligomers formed.
采用密度泛函理论（B3LYP//6-311+G*）计算方法，包括泊松-玻尔兹曼隐式溶剂模型和自由能校正，来研究甲基乙二醛的水合作用以及随后在溶液中形成二聚体物种的过程。我们的计算结果表明，与乙二醛不同，完全水合的物种在热力学上并不比水合程度较低的物种更有利，二氧戊环环物种也不是热力学阱，这与实验数据一致。相反，我们发现羟醛缩合是甲基乙二醛最有利的低聚反应。这些结果与乙二醛的结果不同，乙二醛由于没有甲基，无法形成导致羟醛缩合的烯醇结构。对于甲基乙二醛，亲核进攻醛基而非酮基的产物更受青睐。我们的结果有助于解释观察到的甲基乙二醛和乙二醛之间的一些差异，特别是形成的不同低聚物阵列。
