Diffusion Studies of Dihydroxybenzene Isomers in Water-Alcohol Systems
Diffusion Studies of Dihydroxybenzene Isomers in Water-Alcohol Systems
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DOI：
10.1021/jp311044a
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发表时间：
2013-03-07
影响因子：
3.3
通讯作者：
Price, William S.
中科院分区：
文献类型：
--
作者：
Codling, Dale J.;Zheng, Gang;Price, William S.
核磁共振扩散研究可以用来识别混合物中的不同化合物。然而，由于扩散系数主要取决于有效流体动力半径，因此在扩散的基础上分辨具有相似大小和结构的化合物（如异构体）是特别困难的。在某些溶液中，物种之间的微分溶液相互作用可以提供分离的可能性。在本研究中，研究了二羟基苯的三种异构体（即（1,2-）儿茶酚，（1,3-）间苯二酚和（1,4-）对苯二酚）在水，水一元醇（即乙醇，1-丙醇，叔丁醇）和水乙二醇中的自扩散。这些体系允许对同分异构和不同溶剂相互作用对扩散的影响进行检验。在水溶液中，这些异构体具有相同的扩散系数，但在水-一元醇体系中，儿茶酚的扩散系数与间苯二酚和对苯二酚的扩散系数不同。一水醇浓度越高，分离越明显。研究了这些差异背后的化学原因。
Nuclear magnetic resonance diffusion studies can be used to identify different compounds in a mixture. However, because the diffusion coefficient is primarily dependent on the effective hydrodynamic radius, it is particularly difficult to resolve compounds with similar size and structure, such as isomers, on the basis of diffusion. Differential solution interactions between species in certain solutions can afford possibilities for separation. In the present study, the self-diffusion of the three isomers of dihydroxybenzene (i.e., (1,2-) catechol, (1,3-) resorcinol, and (1,4-) hydroquinone) was studied in water, aqueous monohydric alcohols (i.e., ethanol, 1-propanol, tert-butanol), and aqueous ethylene glycol. These systems allowed the effects of isomerism and differential solvent interactions on diffusion to be examined. It was found that, while in aqueous solution these isomers had the same diffusion coefficient, in water-monohydric alcohol systems the diffusion coefficient of catechol differed from those of resorcinol and hydroquinone. The separation was found to increase at higher concentrations of monohydric alcohols. The underlying chemical reasons for these differences were investigated.