Ethanol results and a slew of other solvents

16 Oct
Published by RyanPakula
59.27% PZQ was recovered from ethanol heated to 50 ± 2ºC.  NMR was clean, Tm = 138.3 - 138.6ºC.
Began recrystallizations with water, ethanol, 50/50 water/ethanol, toluene, and benzene.
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The crystals from EtOH, heated to 50 ± 2ºC then cooled to RT then 5ºC overnight, didn't look particularly nice, but they were isolated and washed with a few milliliters of cold ethanol, then put under high vac for 30 m.  Some PZQ went through, as evidenced by crystals in the filter flask.  The recovered mass was 137.1 mg, and, having started with 231.3 mg, there was 59.27% recovered material.  NMR in d-chloroform looked clean (I'll post this once I figured out how to put spectra in jcamp-dx format, as well as the spectrum of PZQ out of the bottle), and the melting point was 138.3 - 138.6ºC (@ 1ºC/min).
 
I began recrystallizations with water, ethanol, 1:1 v/v water:ethanol, benzene, and toluene, all of 250 ± 5 mg PZQ, all at 48 ± 2ºC.  10 mL of water succeeded only in spreading PZQ over the walls of the vial.  The 50/50 mixture wasn't as bad, but 10 mL was still insufficient to dissolve the PZQ.  Toluene dissolved 254.3 mg PZQ with only 3 mL; benzene took 1.4 mL for 246.2 mg PZQ, and this time 2.2 mL EtOH was needed to dissolve 245.8 mg PZQ (up from 1.6 mL last time for 231.3 mg...) (i.e., 111.7 mg/mL this time vs. 144.6 mg/mL last time)
 
I let these cool to RT and put them into the fridge for the weekend.  Prior to putting them away though, I added hexanes to the EtOH to see if I could increase the yield.  No PZQ crashed out upon addition of hexanes, which was unexpected.