Mixed Crystals in Chiral Organic Systems: A Case Study on (R)- and (S)‑Ethanolammonium 3‑Chloromandelate

This work focuses on characterization of chiral organic systems with partial solid solutions. Particularly, behavior of the (R)- and (S)-ethanolammonium 3-chloromandelates (E3ClMA) has been investigated experimentally. Partial solid solutions of the series (R)-E3ClMA–(Rac)-E3ClMA and (S)-E3ClMA–(Rac)-E3ClMA were discovered at the eutectic type of the binary phase diagram by means of systematic differential scanning calorimetry and X-ray powder diffraction measurements. Solubility and metastable zone width were measured for solutions of (R)-E3ClMA, (Rac)-E3ClMA, and their mixtures in ethanol as the solvent. The crystal structure of the pure (R)-E3ClMA was successfully determined by single-crystal X-ray diffraction. Several efforts of single crystals productions from (R, S) solutions were made by means of cooling and evaporation methods. Crystal morphology changes from well-shaped crystals for the pure enantiomer to spherulites for the racemic composition.