Thermal Studies on Rubidium Dinitramide

The present study has been carried out to investigate conflicting reports in the literature on the nature of the thermal decomposition of the energetic oxidant rubidium dinitramide in the liquid state. The techniques employed included DSC, simultaneous TG-DTA, simultaneous TG-mass spectrometry and thermomicroscopy. The measurements were supplemented by quantitative chemical analysis of the reaction products. The results showed that, following fusion at 106 °C, the overall decomposition proceeded in a single exothermic reaction stage forming a mixture of rubidium nitrate and rubidium nitrite in the molar ratio 1.2 : 1

Thermodynamics of the deposition of complex waxes and asphaltenes in crude oil

Peer reviewedPublisher PD

Polymorphs and hydrates of acyclovir

Acyclovir (ACV) has been commonly used as an antiviral for decades. Although the crystal structure of the commercial form, a 3:2 ACV/water solvate, has been known since 1980s, investigation into the structure of anhydrous ACV has been limited. Here, we report the characterization of four anhydrous forms of ACV and a new hydrate in addition to the known hydrate. Two of the anhydrous forms appear as small needles and are stable to air exposure, whereas the third form is morphologically similar but quickly absorbs water from the atmosphere and converts back to the commercial form. The high-temperature modification is achieved by heating anhydrous form I above 180°C. The crystal structures of anhydrous form I and a novel hydrate are reported for the first time. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:949–963, 2011Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79417/1/22336_ftp.pd

Crystal polymorphism in a carbamazepine derivative: Oxcarbazepine

Although crystal polymorphism of carbamazepine (CBZ), an anticonvulsant used to treat epilepsy, has been known for decades, the phenomenon has only recently been noted for its keto-derivative oxcarbazepine (OCB). Here it is demonstrated that OCB possesses at least three anhydrous polymorphs. Although all forms are morphologically similar, making differentiation between crystal modifications by optical microscopy difficult, powder X-ray diffraction, Raman spectroscopy, and thermomicroscopy show distinctive differences. These techniques provide an efficient method of distinguishing between the three polymorphs. The crystal structure of form II of OCB is reported for the first time and the structure of form I has been redetermined at low temperature. Remarkably, both the molecular conformation and crystal packing of form II are in excellent agreement with the blind prediction made in 2007. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:794–803, 2010Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/64542/1/21873_ftp.pd

Unmasking a Third Polymorph of a Benchmark Crystal-Structure-Prediction Compound

No AbstractPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/64322/1/anie_200903285_sm_miscellaneous_information.pd

Wax Chemical and Morphological Investigation of Brazilian Crude Oils

The waxes in petroleum can precipitate and form unwanted gels and deposition when exposed to low temperatures. The idea of this chapter is to approach methods of quantification and physicochemical and morphological characterization of waxes and how this information can help in understanding this deposition. Information such as the quantity of waxes and the chemical structures in the oil is fundamental to predict the possible deposition and its ability to aggregate with other crystals. For example, the knowledge about the wax morphology may contribute to explain the nucleation and growth of the deposits. The polarized light microscopy, the most common technique to visualize wax crystals, and the bright-field microscopy, the most simple technique, able to show crystal details that have not been seen on the polarized light, was used

Estudio de preformulación para el desarrollo de comprimidos de indometacina como substancia policristalina

Se desarrolla a través del polimorfismo de Indometacina un estudio de preformulación de cara a su posteriorformulación farmacéutica. De los diversos métodos ensayados para la cristalización de los morfos de mayor interésfarmacéutico, el procedimiento de enfriamiento a partir de soluciones concentradas de Acetona:Agua y Etanol:Aguaa altas temperaturas ha permitido, según el caso, obtener éstos de forma pura y con rendimientos mayores del 80%.Las técnicas fisico-químicas de caracterización empleadas han sido las de Termomicroscopía, Microscopía electrónica,Espectroscopía I.R., Rayos X y Calorimetría diferencial de barrido. Además, se han incorporado otras metódicasde interés farmacéutico como son Velocidad de disolución, Tamaño de partícula, Densidad, Fluidez, Porosidad,Superficie específica, Compresibilidad y Dureza con el fin de elegir la forma cristalina más adecuada

New form discovery for the analgesics flurbiprofen and sulindac facilitated by polymer-induced heteronucleation

The selection and discovery of new crystalline forms is a longstanding issue in solid-state chemistry of critical importance because of the effect molecular packing arrangement exerts on materials properties. Polymer-induced heteronucleation has recently been developed as a powerful approach to discover and control the production of crystal modifications based on the insoluble polymer heteronucleant added to the crystallization solution. The selective nucleation and discovery of new crystal forms of the well-studied pharmaceuticals flurbiprofen (FBP) and sulindac (SUL) has been achieved utilizing this approach. For the first time, FBP form III was produced in bulk quantities and its crystal structure was also determined. Furthermore, a novel 3:2 FBP:H 2 O phase was discovered that nucleates selectively from only a few polymers. Crystallization of SUL in the presence of insoluble polymers facilitated the growth of form I single crystals suitable for structure determination. Additionally, a new SUL polymorph (form IV) was discovered by this method. The crystal forms of FBP and SUL are characterized by Raman and FTIR spectroscopies, X-ray diffraction, and differential scanning calorimetry. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 2978–2986, 2007Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57336/1/20954_ftp.pd