Structure dependent thermo-reversible dissolution of organic molecules based on β-cyclodextrin complexes and its application in preparetive-scale separation of xylene isomers

This paper describes an interesting structure dependent thermo-reversible dissolution of organic molecules in the presence of β-cyclodextrin (β-CD) in N, N-dimethyllformamide (DMF). β-CD could influence the solubility of dissolved organic molecules, resulting in the precipitation of organic molecule–β-CD complex from the original transparent solution as the temperature is increasing, while the precipitate will be dissolved again upon cooling. Different organic molecule–β-CD complex precipitates corresponded to different turbid temperatures (Tt). No precipitates were observed solely for either organic molecules or β-CD in DMF when the temperature increased, indicating the structure dependent recognition of β-CD to organic molecules. This molecular recognition behavior had been successfully applied in the separation of xylene isomers in preparative scale.

Varieties of small organic molecules can be precipitated in DMF by β-CD in the form of inclusion complex at different temperatures by a molecular recognition thermo-reversible process. The finding was successfully applied for the separation of xylene isomer mixtures in a preparation-scale in DMF solution.Figure optionsDownload as PowerPoint slideHighlights
► An unusual structure dependent thermo-reversible precipitation–dissolution behavior was reported.
► Varieties of small organic molecules could be precipitated/dissolved in the presence of β-CD by heating/cooling in DMF.
► They can form organic molecules–β-CD complex by heating.
► Different organic molecule–β-CD complex precipitates corresponded to different temperature.
► This behavior was successfully applied for the separation of xylene isomer mixtures in DMF solution.