Journal of Pharmaceutical Sciences 1993-07-01

Phase diagram of (R)- and (S)-4-hydroxy-2-pyrrolidone mixtures: a new case of a conglomerate-forming system.

G Di Silvestro, G Palmisano, R Pellegata

Index: J. Pharm. Sci. 82(7) , 758-60, (1993)

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Abstract

The phase diagram of (R)- and (S)-4-hydroxy-2-pyrrolidone presents a conglomerate in the racemic mixture. The enthalpy of melting extrapolated by the Schröder-van Laar-Le Chatelier equation [change in enthalpy (delta H) = 28410 J/mol; melting temperature (TA) = 429.9 K; solidus temperature (Ts) = 395.4 K] and the value determined by differential scanning calorimetry (delta H = 28494 J/mol; TA = 429.6 K; Ts = 394.6 K) are in excellent agreement. The experimental entropy of the mixing of enantiomers is 5.69 J/mol.K. The conglomerate nature of the racemic mixture was confirmed by X-ray and IR spectroscopy. The presence of solvates was also observed.