A bug in enantiomer separation: double salt formation – diastereomeric and double salt structures of 1-cyclohexylethylammonium 2- and 4-chloromandelate

De, Sourav; Bereczki, Laura; Zodge, Amit; Kőrösi, Márton; Holczbauer, Tamás; Székely, Edit; Bombicz, Petra

doi:10.1107/s0108767321085135

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“…The solubility of R−S was 3-fold greater than that of S−S at a high temperature (40 °C). This means that S−S would be preferentially precipitated into a solid form solution prior to the more soluble isomer R−S, 31 which further laid a thermodynamic foundation for the acquisition of the conglomerate. Therefore, it can be further concluded that the two racemic compounds could successfully convert into the conglomerate as shown in Scheme 1(ii), and then the availability of chiral resolution in this system was verified by preferential crystallization to obtain both enantiomers.…”

Section: Structural Analyses Of R−s and S−smentioning

confidence: 99%

Case of Chiral Resolution through Converting Two Racemic Compounds into a Conglomerate

Wang

Sui

et al. 2023

Crystal Growth & Design

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The formation of a conglomerate is always attractive, which is a prerequisite for chiral resolution by a flexible and productive preferential crystallization. This present study is aimed at exploring the possibility of chiral resolution in a two racemic compound system. The racemic conglomerate of S–S and R–R was prepared by slurring RS-naproxen (RS-NAP) with RS-1-(2-naphthyl) ethylamine (RS-NEA), which was determined by powder X-ray diffraction, differential scanning calorimetry, single-crystal X-ray diffraction, and ternary solubility phase diagram. Moreover, comparative analysis of the molecular structure, stacking patterns, thermodynamic properties, and intermolecular interactions of S–S and R–S indicates that the S–S crystal is more stable. Finally, the feasibility of chiral resolution in isopropanol was explored through a seeded isothermal preferential crystallization mode, and alternative crystallization of S–S and R–R was achieved with recycling the mother liquors.

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Section: Structural Analyses Of R−s and S−smentioning

confidence: 99%