Department of Applied Chemistry and Institute of Molecular Science , National Chiao Tung University , Hsinchu 30010 , Taiwan.
Center for Emergent Functional Matter Science , National Chiao Tung University , Hsinchu 30010 , Taiwan.
J Phys Chem B. 2019 Dec 19;123(50):10663-10671. doi: 10.1021/acs.jpcb.9b08557. Epub 2019 Dec 11.
The acyclic form of monosaccharides exists in a structural equilibrium, with aldose having the aldehyde group and ketose the ketone group (ketose-aldose equilibrium). A basic catalyst facilitates their transformation, which affects the chemical properties of the monosaccharide. In this study, we investigated the ketose-aldose transformation of 1,3-dihydroxyacetone (1,3-DHA), one of the simplest systems of the ketose-aldose equilibrium. We examined the effects of piperidine as the basic catalyst and used IR electroabsorption spectroscopy to study the responses to an external electric field. We analyzed the changes in IR absorption by considering the changes in the molecular orientation and number of molecules in response to the external electric field. The results of the analysis revealed the permanent dipole moment μ, an angle η between μ and μ (the transition moment of the molecular vibration), and the equilibrium constants. The ketose-aldose transformation of 1,3-DHA can be explained in terms of the equilibrium of three states. In the presence of piperidine, a five-state equilibrium was concluded. On the basis of the experimental data, we propose plausible models of dihydroxyacetone, -enediols, -enediol, or glyceraldehyde for each state. The results of our structural analysis of these tautomers provide a detailed understanding of the ketose-aldose transformation of acyclic saccharides and the effects of the basic catalyst.
单糖的开链形式存在结构平衡，醛糖具有醛基，酮糖具有酮基（酮糖-醛糖平衡）。碱性催化剂促进了它们的转化，这影响了单糖的化学性质。在这项研究中，我们研究了最简单的酮糖-醛糖平衡体系之一 1,3-二羟基丙酮（1,3-DHA）的酮糖-醛糖转化。我们考察了哌啶作为碱性催化剂的效果，并使用红外电吸收光谱研究了对外电场的响应。我们通过考虑分子在外电场作用下的取向和数量变化来分析红外吸收的变化。分析结果揭示了永久偶极矩 μ、μ 与 μ 之间的角度 η（分子振动的跃迁矩）以及平衡常数。1,3-DHA 的酮糖-醛糖转化可以用三种状态的平衡来解释。在哌啶存在下，得出了五态平衡的结论。基于实验数据，我们为每个状态提出了合理的二羟丙酮、烯二醇、烯二醇或甘油醛模型。对这些互变异构体的结构分析结果提供了对开链糖的酮糖-醛糖转化以及碱性催化剂影响的详细理解。
