The Self-Disproportionation of Enantiomers (SDE) of α-Pinene via Evaporation off Silica Gel and Foam Fractionation—Validation of the Plausibility of SDE via Gas Chromatography (GC) for α-Pinene

Separations

article

Alicja Wzorek¹  Vadim A. Soloshonok²  Karel D. Klika⁴ 

[1] Institute of Chemistry, Jan Kochanowski University in Kielce, Uniwersytecka 7;Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country;IKERBASQUE, Basque Foundation for Science;Molecular Structure Analysis, German Cancer Research Center

关键词: self-disproportionation of enantiomers (SDE);    α-pinene;    hydrocarbons;    gas chromatography;    silica gel;    foam fractionation;    evaporation;    2D chiral-based association packing;    molecular associations;    intermolecular interactions;   

DOI  :  10.3390/separations10070382

学科分类：社会科学、人文和艺术（综合）

来源: mdpi

【 摘 要 】

α-Pinene is an intriguing monoterpene as it has been reported to undergo the self-disproportionation of enantiomers (SDE) phenomenon via gas chromatography (GC), the only compound to decisively demonstrate this. Examples of the SDE involving the gaseous phase—sublimation aside—are extremely rare. Attempts to replicate the GC results were unsuccessful, though the authors argued convincingly for the difficulty of observing the phenomenon. However, we could effect for α-pinene SDE via evaporation off silica gel and by foam fractionation—albeit the SDE magnitude for both was only very slight—to confirm that α-pinene can undergo the SDE for processes involving a gaseous phase and thus validate the plausibility of the GC report. The indications are that the molecular associations responsible for the various SDE observations of α-pinene occur not in the gaseous phase or the bulk phase but rather in two-dimensional (2D) adsorbed monolayers and are not based on conventional functional group-based intermolecular interactions and instead are, most likely, as a result of homo- and heterochiral packing differences in the 2D monolayers—a well-known 2D chiral-based association packing effect. These are also the first reports of the occurrence of the SDE using an adsorptive bubble separation process (foam fractionation) and involving a gaseous phase other than sublimation, GC, and distillation.

【 授权许可】

CC BY