High-pressure recrystallisation—a route to new polymorphs and solvates of acetamide and parabanic acid

High-pressure diffraction studies of molecular organic solids. A personal view

“…At the same time, they can find important applications in molecular electronics and in the pharmaceutical industry (Boldyreva & Boldyrev, 1999;Shakhtshneider et al, 1999;Hemley & Dera, 2000;Boldyreva, Shakhtshneider et al, 2000;Katrusiak, 2001;Boldyreva, 2003a,b;Fabbiani et al, 2003Fabbiani et al, , 2004Boldyreva, Drebushchak, Paukov et al, 2004;Boldyreva, Drebushchak, Shakhtshneider, Ahsbahs, Uchtmann et al, 2004;Fabbiani, Allan, Marshall et al, 2005Fabbiani et al, 2006Fabbiani et al, , 2007Boldyreva, 2006Boldyreva, , 2007a.…”

“…Crystallization at high pressure has been known for a very long time, but its systematic application for obtaining new polymorphs and solvates started only a few years ago (Fabbiani et al, 2003(Fabbiani et al, , 2004Fabbiani, Allan, Marshall et al, 2005;Fabbiani et al, 2007). Some of the high-pressure polymorphs and solvates were never before observed at ambient conditions, also those forms that turned out to be quenchable to ambient pressure.…”

Preparation and Evaluation of an Elusive Polymorph of Mefenamic Acid by High Pressure Techniques

“…Polymorphism remains one of the major challenges for both the industry and academic sectors. The development of complementary methods with better control on the crystallization conditions, and more importantly the understanding of factors that result in different packing arrangements of organic molecule in the solid state would therefore be highly desirable [8].…”

“…This has successfully been used to generate new polymorphs of simple compounds e.g. new polymorphs of parabanic acid [8], urea [16], acetamide and paracetamol [8,17].…”

Structural studies of cyclic ureas: 2. Enthalpy of formation of parabanic acid

“…Attempts to obtain other polymorphs using a range of solvents proved unsuccessful, leading the authors to conclude that ''it is unlikely that additional polymorphs of 3 will be readily found as persistent metastable forms" [31]. Using high-pressure crystallization, Fabbiani et al succeeded in isolating and determining the structure of a sesquihydrate of 3 [35]. They report the results of a high-pressure powder neutron diffraction study on parabanic acid-d 2 , which shows that up to a pressure of 2.1 GPa direct compression does not induce a phase transition although several intermolecular interactions are substantially altered.…”