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The preparation, X-ray crystal structures, and thermal analyses of five solvates of the non-nucleoside reverse transcriptase inhibitor Nevirapine are reported. Thermogravimetric traces for the solvates indicated the following compositions (N ) nevirapine): N • (ethyl acetate) 0.5 (1), N • (dichloromethane) 0.5 (2), N • (toluene) 0.5 (3), N • (water) 0.5 (4), and N • (1,4-dioxane) 1.5 (5). Centrosymmetric, hydrogen-bonded nevirapine dimers occur in the crystals of 1-3 and in a previously characterized, unsolvated form of the drug 6. In crystals of 4, drug molecules are linked by a single N-H • • • OdC hydrogen bond only, whereas solvate 5 contains noncentrosymmetric nevirapine dimers. Solvent molecules in 1-3 occupy channels, whereas the water molecules in 4 occupy isolated sites and 1,4-dioxane molecules in 5 occupy layers. These inclusion modes are described with reference to the thermal behaviors of the solvates recorded in TGA and DSC.

X-ray structural and thermoanalytical data for a series of solvates 2-7 of the anti-HIV drug nevirapine containing primary alcohols CH 3 (CH 2 ) n OH with n = 2-7 are reported. The structures of 2-7 are based on a common isostructural framework comprising centrosymmetric hydrogen-bonded nevirapine dimers and contain a common channel parallel to the crystal b-axis whose repeat length spans a narrow range (*8.43-8.52 Å ) in the series and accommodates the various solvent molecules in 2-7. Thermogravimetry yielded a guest-host ratio close to 0.5 for the 1-butanol solvate 3 and a steady decrease in this ratio from 0.43 to 0.32 for the solvates 4-7. This anomalous stoichiometric variation was resolved following successful X-ray analysis of solvate 3 which revealed that the length spanned by the disordered 1-butanol molecule is commensurate with the channel periodicity b, resulting in a stoichiometric compound. Instead, solvates 5-7, for which single crystal X-ray data were available, showed significant disorder for the solvent molecules, attributed to their increasing chain lengths being incommensurate with the parameter b.

Three non-isostructural solvates of the antibacterial dapsone (DDS) containing dichloromethane [DDS•0.5(DCM)], 1,4-dioxane [DDS•DXN], and tetrahydrofuran [DDS•THF] were prepared and characterized by X-ray diffraction (XRD) and thermal analysis, the latter including hot stage microscopy (HSM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). In addition, their thermal desolvation was investigated by isothermal kinetic studies which indicated the A2 model as the best fit for desolvation of the DCM and DXN solvates, while the R2 model was indicated for the THF solvate. Activation energies for desolvation of these new species were in the range 141−173 kJ mol −1 . Attempts were made to reconcile the kinetic models with the observed HSM desolvation behavior and the modes of solvent inclusion within the solvate crystals determined by XRD (viz. isolated sites for the DCM solvate and channel-type for the others).

When anhydrous nevirapine was recrystallized from ethanol that contained increasing amounts of water, it was found that the amount of water affected not only the solubility but also the solvent inclusion and crystal habit of the precipitated material. This led to the crystallization of a previously unknown nevirapine hemiethanolate from solutions that contained less than 5% water. Adding more than 10% water led to the isolation of the known hemihydrate, and a further increase in water-content caused precipitation of the anhydrous form. It was shown not only that discontinuities in the solubility profile indicate transition from one crystal form to another but also that they occurred at the junction between two distinct crystal forms or crystal habits. A possible explanation for these observations was found in the relationship between the solubility of nevirapine, the solubility parameter of the solvent mixtures, and the change in water activity.

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A low-kilojoule honeybush iced tea powder mixture will retain its functional phenolic compounds and physicochemical properties during shelf-life storage at 25 °C for 6 months. © 2017 Society of Chemical Industry.