15 Oct
Published by RyanPakula

Toluene worked less-than-nicely for recrystallization, and a column to isolate the yellow/brown product failed.  This is likely due to the fact that a crude NMR of this product looks 99% identical to PZQ from the bottle.
I tried dissolving the 8.6065 g PZQ from the other day in toluene.  3 mL was insufficient at 85ºC, as was 4 mL.  At this point, the solution was yellow.  I TLCed the oil and the solid from before.  A higher Rf spot is present in both "products" that isn't present in the PZQ lane (visible only by UV, whereas PZQ is visible by UV, iodine, and vanillin [and ninhydrin, but vanillin is much nicer]).  I took a few milliliters of this yellow toluene/PZQ mixture, rotovapped to dryness, and ran it on a column: 1000 mL 30% EtOAc in hexanes, 500 mL 40%, 500 mL 50%.  Nothing came off, so I flushed with pure EtOAc.  This had PZQ in it...  I triple-checked my TLCing, but I didn't see anything.  Doing what I should have before, I took a crude NMR of the yellow product, but I saw only PZQ peaks, with maybe one stray peak that wasn't present before.  Hopefully the yellow color is something so small in amount, and soluble still upon cooling!, that it doesn't matter.
I also checked the melting point of our PZQ from the bottle.  I saw 138.9 - 140.3ºC (@ 6ºC/min).  This is a bit higher than the literature (see post from 2 days ago).


MatTodd's picture

Ryan - nice. Can we see JCAMP-DX spectra of PZQ from the bottle, and the yellowed product? Should be able to attach those to a post so everyone can see.
Are you saying that EtOH is best, here? Maybe we should begin that Results Summary page now.
Are you avoiding benzene for health reasons? :)