a. Faculty of Chemistry, University of Latvia, Kr. Valdemara 48, Riga 1013, Latvia

The phase transition kinetics of two chenodeoxycholic acid polymorphic modifications-. form I (stable at high temperature), form III (stable at low temperature) and the amorphous phase has been examined under various conditions of temperature and relative humidity. Form III conversion to form I was examined at high temperature conditions and was found to be non-spontaneous, requiring seed crystals for initiation. The formation kinetic model of form I was created incorporating the three-dimensional seed crystal growth, the phase transition rate proportion to the surface area of form I crystals, and the influence of the amorphous phase surface area changes with an empirical stage pointer q that contained the incomplete transition of the amorphous phase to form I with a residue ωA∞. The extent of transition and the phase transition rate constant depended on form I seed crystal amount in the raw mixture, and on the sample preparation. To describe phase transition kinetic curves, we employed the Runge-Kutta differential equation numeric solving method. By combining the Runge-Kutta method with the multi-point optimization method, the average quadratic deviation of the experimental results from one calculated series was under 2%.

a. Faculty of Chemistry, University of Latvia, Kr. Valdemara 48, Riga 1013, Latvia

All four known xylazine hydrochloride polymorphous forms were obtained and their relative stabilities were compared directly at three different temperatures. At higher temperatures, it is possible to determine the relative stability of all forms directly by measuring the changes in the composition of the mixtures of two polymorphous forms using powder x-ray diffraction methods. At lower temperatures, a solvent was added to the mixture and the changes in composition were determined. Polymorph transition temperatures were determined directly. To predict the transition temperature which was not found using the direct method, the polymorph melting data and determined transition temperatures were used. A phase stability diagram was constructed from the acquired data. The stability of all anhydrous polymorphous forms was compared in the presence of water vapor pressure that was higher than the equilibrium pressure.

a. Faculty of Chemistry, University of Latvia, Kr. Valdemara 48, Riga 1013, Latvia

The crystal structure of the title compound, 2C 19H17N2+·C4H 2O42-, consists of centrosymmetric trimers built up of two crystallographically independent N,N′-diphenyl-benzamid- in-ium cations and one fumarate dianion, which is located on a centre of inversion. The components of the trimers are linked by N-H⋯O hydrogen bonding. In the cation, the outer rings make dihedral angles of 53.66 (5) and 78.38 (5)° with the central ring. The two outer rings make a dihdral angle of 81.49 (5)°.

a. Faculty of Chemistry, University of Latvia, Kr. Valdemara 48, Riga 1013, Latvia

b. Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, Helsinki 00014, Finland

Crystal structures of alpha2-adrenergic antagonist atipamezole base (1) and its hydrochloric acid salt (2) have been determined using X-ray diffraction methods. Atipamezole base crystallized in the monoclinic space group P21, with unit cell parameters a = 13.238(4), b = 9.747(4), c = 14.609(5) Å, β = 107.75(4)°, V = 1,795.3(12) Å3 and Z = 6 (three independent molecules of 1). Atipamezole hydrochloride crystallized in the monoclinic space group Cc, with unit cell parameters a = 12.052(1), b = 32.561(9), c = 13.668(5) Å, β = 102.64(1)°, V = 5,233(2) Å3 and Z = 16 (four independent molecules of 2). Each of the three atipamezole moieties in 1 has an intramolecular C-H⋯;N H-bond. In both structures the molecules are H-bonded to form extended chains.