A compendium of phase change enthalpies published in 2010 is updated to include the period 1880–2015. Phase change enthalpies including fusion, vaporization, and sublimation enthalpies are included for organic, organometallic, and a few inorganic compounds. Part 1 of this compendium includes organic compounds from C1 to C10. Part 2 of this compendium, to be published separately, will include organic and organometallic compounds from C11 to C192. Sufficient data are presently available to permit thermodynamic cycles to be constructed as an independent means of evaluating the reliability of the data. Temperature adjustments of phase change enthalpies from the temperature of measurement to the standard reference temperature, T = 298.15 K, and a protocol for doing so are briefly discussed.

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2015. Part 1. C1-C10

The structural response of the nootropic drug piracetam (2-oxo-pyrrolidineacetamide) to both direct compression and high-pressure recrystallization from aqueous solution is reported. Crystals obtained by these methods have been characterized in situ by single-crystal X-ray diffraction. Compression of form II between pressures of 0.45-0.70 GPa caused a reversible, single-crystal to single-crystal transition to give a new polymorph, form V. Crystallization from a dilute aqueous solution of piracetam at a pressure of 0.6 GPa via crystallization of high-pressure ice-VI resulted in the formation of a previously unreported dihydrate. The molecular packing arrangements of these new structures are compared with the known polymorphs and hydrates of piracetam. This study highlights how the systematic variation of pressure is a powerful method for the exploration of polymorphism and solvate formation and has the potential to add a further dimension to polymorph screening of pharmaceuticals.

High-pressure studies of pharmaceuticals: An exploration of the behavior of piracetam

Some improvements have been introduced in the current computer program for powder diffraction pattern indexing using the dichotomy algorithm. The resulting version, DICVOL14, includes optimizations and extension of scanning limits for triclinic cases, a detailed review of the input data from the indexing solutions, cell centering tests and a new approach for zero-point offset evaluation. The performance of the new version is illustrated with many examples, such as triclinic cases with long axes and dominant zones. Some important parameters in pattern indexing based on the dichotomy algorithm are commented upon, e.g. the precision of data and spurious lines.

Some further considerations in powder diffraction pattern indexing with the dichotomy method

Quantitative polymorph contaminant analysis in tablets using Raman and near infra-red spectroscopies.

X-ray Characterization of the Triclinic Polymorph of Carbamazepine

Phenomenology of Polymorphism, III:p,TDiagram and Stability of Piracetam Polymorphs

Morphology of C60 decagonal crystals grown from n-hexane

The molecular structure of the title compound comprises two nearly orthogonal planar systems. The main feature of the crystalline structure is the existence of C-H---O interactions linking two molecules about the centers of inversion. From crystallographic data, charges and interaction enthalpy are calculated for the monomer and the dimer by means of the AM1 (Austin model 1) semi-empirical method. A substantial stabilization of the molecular structure through dimer formation is observed

http://journals.iucr.org/c/issues/1993/05/00/pa0282/pa0282.pdf

Structure of N-(2,6-dimethylphenyl)-5-methylisoxazole-3-carboxamide and molecular-orbital study of C–H⋯O bonded dimers

Crystal structure determination, semiempirical AM1 and PM3 calculations have been performed on 2,4-dimethyl-1H-naphtho[2,3-b][1,4]diazepine hydropicrate. The two molecules are almost planar apart from two NO2 and CH3 groups. The NO2 plane makes an angle of 36.2° and 44.3° with the least squares plane of the ‘phenyl’ ring. The naphthodiazepine molecule and the picrate acid molecule are intermolecularly linked by one N–H ⋯ O and four C–H ⋯ O hydrogen bonds and form polar ribbons parallel to the [110] direction. The ribbons are linked by intermolecular C–H ⋯ O hydrogen bonds about a centre of inversion and the ensemble forms layers. These layers are weakly bound by van der Waals' interactions and undergo a reversible martensitic-type transition upon heating. During this transition the colour of the crystal changes from dark orange to yellow. AM1 and PM3 calculations on the dimers reproduce, with acceptable approximation, the main features of the structure.

Structure of 2,4-dimethyl-1H-naphtho[2,3-b][1,4]diazepine hydropicrate. Solid-state assembly via C–H ⋯ O hydrogen bonding

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Papers

Phenomenology of Polymorphism, III:p,TDiagram and Stability of Piracetam Polymorphs

Morphology of C60 decagonal crystals grown from n-hexane

Structure of N-(2,6-dimethylphenyl)-5-methylisoxazole-3-carboxamide and molecular-orbital study of C–H⋯O bonded dimers

Structure of 2,4-dimethyl-1H-naphtho[2,3-b][1,4]diazepine hydropicrate. Solid-state assembly via C–H ⋯ O hydrogen bonding