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 singlecrystal 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.

1 : 3 and 1 : 2 discrete compounds are verified in two chiral systems and discussed with respect to known cases in the literature.

Two model compoundsvaline C 5 H 11 NO 2 (L-Val) and isoleucine C 6 H 13 NO 2 (L-Ile)were chosen to study isomorphism of the compounds formed by enantiomeric molecules having similar shapes, but differing in the number of chiral centers. The X-ray powder diffraction method was applied to investigate samples with various ratios of valine and isoleucine crystallized from aqueous solutions by cooling and isothermal methods. Limited solid state miscibility between valine and isoleucine was established. A non-equimolar discrete compound with the molecular ratio Val:Ile = 2:1 (V 2 I) has been discovered, and its crystal structure was determined. Accordingly, the corresponding regions of solid solutions and two-phase areas in-between were distinguished. Solubility data in water support the phase behavior in the system.

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X-Ray diffractometry was employed to investigate the possibility of formation of non-equimolar discrete compounds in the chiral system of malic acid S-and R-enantiomers. Samples studied were mixtures of single enantiomers or an enantiomer and the various polymorphs of the racemic compound. From samples prepared via recrystallization of the melt and grinding of initial reactants, it is demonstrated that the malic acid enantiomers can form stable stoichiometric compounds in S:R ratios of 3:1 and 1:3. Compared to the known racemic and pure enantiomer phases, the corresponding compounds S 3 R/SR 3 are characterized by a proper powder diffraction pattern and melting point.