Separating Enantiomers of Haloalkanes and Alcohols on a Stationary Phase Based on the Supramolecular Structure of Melamine with Induced Chirality
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A new chiral stationary phase is proposed that is based on the supramolecular structure of melamine self-assembled in the mode of the induction of chirality. Induction is achieved via mechanical stirring in accordance with the Kondepudi effect in order to form a layer of a supramolecular structure with predominantly one type of chiral supramolecular domains on the surface of the sorbent. The resulting inert support with 1% melamine is used for the gas chromatographic separation of enantiomers of 2-butanol, 1‑methoxy-2-propanol, 2-bromobutane, 2-chlorobutane, and 2-bromopentane. The coefficients of selectivity and the separation of enantiomers are calculated. No separation of enantiomers is observed on a column conditioned at 100°C. After conditioning the column at 200°C, a series of successful separations of racemates is obtained in the 60–110°C range of temperatures. The highest coefficient of selectivity for haloalkanes is obtained at 70–75°C, so 2-bromobutane has α = 1.62 at 70°C, 2-chlorobutane has α = 1.23 at 75°C, and 2‑bromopentane has α = 1.68 at 70°C. The coefficients of selectivity for 2-butanol and 1-methoxy-2-propanol are highest at 80 and 100°C (α = 1.45 and 2.24), respectively. It is assumed that the ability of the suprastructure of melamine to exhibit enantioselectivity is associated with the formation of cavities capable of chiral recognition.
Keywords:enantiomers melamine inert support 2-halosubstituted alkanes gas chromatography supramolecular structure induction of chirality Kondepudi effect coefficient of selectivity
This work was supported by a grant from the Russian Science Foundation, project no. 17-73-10181.
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