The structure of chiral phenylethylammonium montmorillonites in ethanol-toluene mixtures
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Chiral phenylethyl alkylammonium montmorillonites were prepared by ion exchange of Na montmorillonite (from Wyoming). The structure of chiral montmorillonite organocomplexes was studied in the dry state by X-ray diffraction, IR spectroscopy and 13C cross-polarized MAS NMR and after swelling by X-ray diffraction. The phenylethylammonium ions are intercalated in montmorillonite in a monolayer structure, while higher derivatives containing alkyl chains with lengths of nc=10−16 take up a bilayer orientation. The hydrophobized clay mineral is readily dispersed in organic solvents, for example in ethanol, toluene and their binary mixtures. Due to selective adsorption, the liquids penetrate into the interlamellar space under significant interlayer expansion producing a great variety of alkyl chain orientations within the interlamellar space, depending on the length of alkyl chains and on the mixture composition. Such interlamellar spaces are possible chiral nanoreactors with adjustable volume and may be prospectively utilized for shape-selective catalytic reactions and the production of enantiomers.
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