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For decades, carbamazepine (CBZ) has served as a model compound for groupsengagedinthestudyofcrystalpolymorphism.Despiteconsiderableeffort,crystal structures for only three of its four anhydrous forms have previously been determined. Herein, we report the first single crystal X-ray structure of the high temperature modi- ficationofCBZ(formI).FormIcrystallizesinatricliniccell(P-1)havingfourinequivalent molecules with the following lattice parameters: a ¼5.1705(6), b ¼20.574(2), c ¼ 22.245(2) A ˚ , a ¼84.12(4), b ¼88.01(4), and g ¼85.19(4)8. Furthermore, we compare the physical properties of the four anhydrous polymorphs of CBZ, including the first comprehensivecharacterizationofformIV.Substantialdifferencesareseenamongthese forms by powder X-ray diffraction, infrared spectroscopy, thermomicroscopy, and differential scanning calorimetry. These data are correlated to their respective crystal structures for the first time. We have found that all polymorphs possess identical strong hydrogen bonding patterns, similar molecular conformations, and stabilities that are within 0.7 kcal/mol of each other. 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2260-2271, 2003 |
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