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- 2014 (3) (entfernen)
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- Crystallization (1)
- In situ Raman spectroscopy (1)
- In situ WAXS (1)
- Polymorphism (1)
- ROY (1)
- caffeine (1)
- cocrystal (1)
- synchrotron X-ray diffraction (1)
The synthesis of the polymorphic cocrystal caffeine:anthranilic acid was investigated to obtain a better understanding of the processes leading to the formation of different polymorphic forms. In the case of these cocrystal polymorphs synthesized by liquid-assisted grinding a distinct influence of the dipole moment of the solvent was found. A pre-coordination between the solvent molecules and the caffeine:anthranilic acid cocrystal could be identified in the formation of form II. In the case of form II the solvent can be regarded as a catalyst. The formation pathway of each polymorph was evaluated using synchrotron X-ray diffraction.
Die quantitative NMR-Spektroskopie (qNMR) gewinnt in den letzten Jahren immer mehr an Bedeutung, speziell hinsichtlich der Anwendung auf komplexe Fragestellungen der analytischen Chemie. Ein großer Vorteil dieser Methode ist die Möglichkeit der Relativquantifizierung durch das „Zählen von Kernspins" in der Probe. Unter der Voraussetzung eines korrekt ausgeführten NMR-Experiments ist so der direkte Vergleich von Signalflächen im Spektrum möglich, ohne dass zuvor zwingend eine Kalibrierung notwendig ist.
The crystallization of a highly polymorphic compound was studied in situ by combined time-resolved X-ray diffraction and Raman spectroscopy. Any influences of solid surfaces, temperature, and humidity on the crystallization were omitted by the use of a specially designed acoustic levitator. Investigations of polymorphic phase transitions during the crystallization process in different solvents allowed a structure assignment from first crystalline assemblies to final crystalline form. For the first time, it was possible to yield pure phases of selected polymorphs of the model compound ROY (5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile) directly from solution. The influence of the solvent on the final products and transient phases during the crystallization process was elucidated.