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Physical & Chemical properties

Melting point / freezing point

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Description of key information

The melting point was determined in a study to characterize different batches of progesterone with respect to their solid state form.
Analytical Development Physical Chemistry, Schering AG Berlin. Study report No. A26513 (ADP 2005_052), dated 2005-04-26.
Result: 130°C (403 K), polymorph I

Key value for chemical safety assessment

Additional information

Progesterone is a solid under ambient conditions. In the literature five anhydrous forms of progesterone are described. The crystal structures of polymorphs I and II were characterized by X-ray analysis on single crystals. Polymorph I melts at 130 °C. Polymorph II melts between 120 and 123 °C. Polymorphs III – V were observed only thermomicroscopically. Their melting points are 111, 106 and 100 °C, respectively.

Polymorph I is the thermodynamically stable form in the whole temperature range.

All production batches and laboratory crystallization products examined in this study consisted of polymorph I. Polymorph II could be obtained from the melt. Additionally, an instable amorphous phase was formed by quenching the melt. The glass transition temperature of the amorphous phase is approx. 11 - 13 °C.