The present paper reports a study on the chiral discrimination at the solid state of methyl 2-(diphenylmethylsulfinyl)acetate (hereafter, DMSAM) as a key intermediate in the synthesis of an acetamide derivative (modafinil). A partial solid solution (i.e., stable “racemic conglomerate” with partial miscibility at the solid state) between enantiomers was characterized by X-ray single crystal analyses and high performance liquid chromatography (HPLC). Binary and ternary phase diagrams of DMSAM were investigated by HPLC measurements, differential scanning calorimetry (DSC), discontinuous isoperibolic thermal analysis (DITA), and Raman spectroscopy. Finally, the distribution of the two enantiomers inside single crystals was studied by dissolution and Raman microspectroscopy.

The antifungal agent ciclopirox ethanolamine (1:1), a stoichiometric compound between ethanolamine and 6-cyclohexyl-1-hydroxy-4-methylpyridin-2-(1H)-one, crystallizes as an anhydrate and a monohydrate. The structures of both phases have been characterized by single crystal X-ray diffraction and suggest that, at ambient temperature, ciclopirox ethanolamine (1:1) anhydrate and monohydrate should be classified as salts from the position of the protons in the Fourier difference map. The thermal dehydration process has been elucidated by thermal analyses (TGA/DSC), temperature resolved X-ray powder diffraction and Hot-Stage Microscopy. Moisture sorption and desorption investigations at room temperature under static and dynamic conditions (DVS) reveal that, if the dehydration is not implemented under a sufficient ethanolamine vapor pressure, the dehydration-hydration mechanism is not reversible. This behavior suggests that, at elevated temperature, ciclopirox ethanolamine (1:1) monohydrate could be contemplated as a heterosolvate of water and ethanolamine molecules.

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