Physicochemical Properties and the Crystallization Thermodynamics of the Pure Enantiomer and the Racemate for N-Methylephedrine

The binary melting point phase diagram of (+)- and (−)-N-methylephedrine was determined. It was shown that (±)-N-methylephedrine is a racemic conglomerate. The enthalpies of fusion of (+)-N-methylephedrine and of (±)-N-methylephedrine and the entropy of mixing of (+)- and (−)-N-methylephedrine were calculated using the thermal data. The nature of the (±)-N-methylephedrine crystalline racemate was also confirmed by means of comparison of solid-state infrared spectra and powder X-ray diffraction patterns of the racemic mixture with those of one of the enantiomers. The solubility and supersolubility diagrams of (±)-N-methylephedrine in a mixed solvent of 2-propanol and water were determined over the temperature range (7 to 30) °C. The ternary phase diagram of (+)- and (−)-N-methylephedrine with the mixed solvent was constructed at (15, 20, 25, and 30) °C.