Polymorphic transitions in crystalline E- and Z-alpha-phenylcinnamic acids followed by DSC

Pálinkó, István and Katona, T. and Trowbridge, L. (1998) Polymorphic transitions in crystalline E- and Z-alpha-phenylcinnamic acids followed by DSC. JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 53 (1). pp. 317-322. ISSN 1388-6150

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Abstract

Polymorphic transitions of alpha-phenylcinnamic acid stereoisomers crystallized from various solvents (CHCl3, ethanol, diethyl ether), precipitated with different acids (acetic acid or HCl) or sublimed have been studied by differential scanning calorimetry (DSC). Measurements were also supplemented by powder X-ray diffractometry (XRD). Polymorphic transitions were not found for any of the E isomer samples irrespective of the method of treatment. However, in heating-cooling cycles reversible transitions could be detected for the Z isomer. On heating an exothermic peak was registered on samples sublimed, crystallized from ethanol or diethyl ether before melting, while samples precipitated by HCl or crystallized from chloroform exhibited more complex transitions. Here, endothermic effects were also observed. Enthalpy values for transformations (either for melting or polymorphic and other transitions) are also given.

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