Ethanol and hexanes - initial results

20 Oct
Published by RyanPakula

V(hexanes) = 0.5*V(EtOH) resulted in the highest recrystallization yield at 74.34%.
Of the four experiments where 50ºC hexanes was added to the saturated 50ºC EtOH solutions (where the volume of hexanes was 0x, 0.5x, 1x, and 2.5x the volume of EtOH needed to solvate the PZQ completely), the recovery percentages were, respectively: 73.53%, 74.34%, 70.90%, and 68.16%.  The motherliquors were chilled to 5ºC try to collect a second crop, but, likely due to the additional volume of solvent used to wash the first crop, no precipitate formed.  I plan to concentrate these, then go for a second crop.
A few details: the 0.5x, 1x, and 2.5x crystals were all washed with a 5ºC 1:1 hexanes:EtOH mixture, while the 0x crystals were washed with 0ºC absolute EtOH.  The respective numbers were: 0x - 220.3 mg from 299.6 mg (1.6 mL 50ºC EtOH), 0.5x - 210.9 mg from 283.7 mg (1.2 mL 50ºC EtOH), 1x - 175.7 mg from 247.8 mg (1.2 mL 50ºC EtOH), 2.5x - 168.7 mg from 247.5 mg (1.2 mL 50ºC EtOH).