Disappearing and Reappearing Polymorphs. The Benzocaine:Picric Acid System

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• 作者：Jan-Olav Henck ; Joel Bernstein ; Arkady Ellern ; and Roland Boese
• 刊名：Journal of the American Chemical Society
• 出版年：2001
• 出版时间：March 7, 2001
• 年：2001
• 卷：123
• 期：9
• 页码：1834 - 1841
• 全文大小：680K
• 年卷期：v.123,no.9(March 7, 2001)
• ISSN：1520-5126

文摘

The low-melting polymorphic modification of the 1:1 complex of benzocaine (BC) and picric acid(PA) had earlier been reported to be an example of a "disappearing polymorph". The BC:PA system has beenreinvestigated by thermomicroscopy, calorimetry, solid-state NMR, and X-ray crystallography. The phasediagram has been derived, and robust procedures for the crystallization of the two 1:1 complexes, a hydrateof the 1:1 complex, and a 2:1 complex have been devised. The structures of all four phases have been determinedand compared using graph set analysis to characterize the hydrogen-bonding patterns. It is shown that thethorough microscopic investigation of the thermal behavior, combined with calorimetric methods, can lead tothe development of strategies to crystallize metastable polymorphic forms which may be difficult to obtainonce their stable congeners have been obtained.