Crystal structure determination, thermal behaviour and phase diagram determination of synephrine and adrenaline optical isomers and racemate

The investigation of the physico-chemical properties of the R- and S-synephrine enantiomers and the L-enantiomer and the racemic compound of adrenaline have been made using X-Ray powder diffraction and differential scanning calorimetry experiments. The enantiomer of synephrine crystallizes in the orthorhombic system (space group P212121, Z=4 , with a = 6.59250 ± 0.00038 à..., b = 7.99147 ± 0.00046 à..., c = 17.03482 ± 0.00126 à...); while the L- and DL- adrenaline crystalize in the monoclinic (space group P21, with a = 7.89723 ± 0.00084 à..., b = 6.79832 ± 0.00053 à..., c= 8.60684 ± 0.00102 à..., β= 97.93536 ± 0.00872°). This method allowed determining a melting temperature and enthalpy of R- or S-synephrine is equal to 176, 60 ± 0,36 °C and 234,19 ± 3,87 J/g, respectively. There are a stable phase diagram including the racemate compound and the metastable one including the conglomerate. The melting temperature of DL-adrenaline is reached at 215,9 ± 0,6 °C and the melting enthalpy is equal to175,9 ± 8,4 J/g. The phase diagram is a rare case of partial solid solution for the conglomerate.