Form I (HT) and form III (LT) of pleconaril are enantiotropically related with a calculated temperature of transition Tτ ) 35.7 °C (supposing an ideal behavior). Structural data obtained from single crystal X-ray diffraction at 100 K and room temperature show that (i) form I (HT) can be described as a network of dimers and form III can be described as a three-dimensional weakly H-bonded network of monomers. (ii) These two varieties contradict the density rule. (iii) The solid-solid transition (not observed) could only occur via a destructive-reconstructive mechanism. Investigations on the pleconaril-ethanol binary system show that the conversion form I S form III at Tτ ) 31 ( 2 °C is only possible when mediated by a solvent. A favorable set of thermodynamical and kinetic conditions allows quantification of form I in form III down to 0.1% by using differential scanning calorimetry. To assess the structural purity, this method could be applied to other compounds fulfilling five restrictive conditions.

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.

Resolution of (±)ibuprofen using S-α-Methylbenzylamine in pure ethanol leads to the enriched S-IBU/S-αMBA diastereomeric salt which crystallizes as very fine needles. In order to improve the filterability and processability of the solid phase, water can be added to the medium and lead to more equant particles that are still elongated. A high fraction of the resulting platelets display on both ends a fluid inclusion containing both liquid and a large bubble of gas. A detailed analysis of the particles reveals that they are not really single crystals but more an ordered association of fibers defined as fibrous crystal. A domain of partial solid solution is evidenced near the pure less soluble diastereomer and its impact on the formation of fibrous crystals is demonstrated. When pure S-IBU/S-αMBA diastereomeric salt is recrystallized in the same medium (e.g., ethanol–water) the crystallinity is improved, but fluid inclusions can still be observed.

No abstract

No abstract