Solvates of acotiamide hydrochloride: characterization and phase transformation.

Five novel crystals of acotiamide hydrochloride (AH) with solvates dimethyl formide (DMF), dimethyl sulfoxide (DMSO), ethyl acetate (EA) and water (W) [1AH‐1W‐1DMF, 1AH‐1DMSO‐I, 1AH‐1DMSO‐II, 1AH‐1W‐1DMSO and 2AH‐2DMSO‐1EA] were characterized using single‐crystal X‐ray diffraction, powder X‐ray diffraction, thermal analysis and Fourier transform infrared spectroscopy. The five crystals can be divided into four distinct structural types based on analysis of their similarities; 1AH‐1W‐1DMF and 1AH‐1W‐1DMSO are isostructural. The benzene rings in 1AH‐1DMSO‐I, 1AH‐1DMSO‐II and 2AH‐2DMSO‐1EA can rotate 180°, and the intramolecular hydrogen bond changes from an OH...C=O bond to an NH...OH bond relative to what is seen in 1AH‐1W‐1DMF and 1AH‐1W‐1DMSO. Phase transformation experiments show that a humidity‐induced phase transformation is closely tied to moisture content. [ABSTRACT FROM AUTHOR]