RyanPakula's blog

21 Jan

Sulfur melt data smogasbord

Published by RyanPakula

I've been working on the sulfur melt reaction, trying to optimize the reaction yield of the singly dehydrogenated product (DHP below).  Many studies have been conducted, and here I'll discuss some of what I've found out.
 

26 Nov

Developing a GC assay

Published by RyanPakula

Recent work has been towards developing a GC assay to quickly monitor the sulfur melt reactions.
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04 Nov

InChI

Published by RyanPakula

InChI is great and all, but today while exploring, I found two issues that bugged me.  The first arose from my simple double-checking exercise: I drew praziquantel at http://pubchem.ncbi.nlm.nih.gov/edit/ then took the InChI returned and plugged it into chemspider.com to see if it would bring up the appropriate page for PZQ (which I already knew existed).  I made the mistake of leaving one of the amide nitrogens as a carbon, so my search on chemspider returned that there were no hits at all.  Now, in this case that's fine, cause I messed u

03 Nov

"Successful" dehydrogenation

Published by RyanPakula

The sulfur melt dehydrogenation,

was carried out, with 9.5% isolated yield of the desired product and 69.3% recovered starting material.  Other products (observed by TLC) were not found after the column.
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26 Oct

Dehydrogenation of PZQ and final EtOH recrystallization results

Published by RyanPakula

Trying to dehydrogenate PZQ using elemental sulfur.

Total yields including second batch of recrystallization are 86.4%, 74.34% (no second batch), 78.7%, and 80.1%, respective to 0x, 0.5x, 1x, and 2.5x hexanes volume to ethanol volume.
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20 Oct

Ethanol and hexanes - initial results

Published by RyanPakula

V(hexanes) = 0.5*V(EtOH) resulted in the highest recrystallization yield at 74.34%.
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19 Oct

Ethanol and hexanes

Published by RyanPakula

EtOH with hexanes had wispy crystals; recovery was 43.98%; pure by NMR; Tm = 138.2-138.8ºC.  No crystals had formed from benzene sl'n nor toluene, so hexanes were added, and vials left at 5ºC.  Began EtOH with varying amounts of hexanes recrystallizations.
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1 mL hexanes was added to the solution of benzene (1.4 mL), and 2 mL hexanes were added to the toluene solution (3 mL).  After a few hours at 5ºC, crystals have begun to form.
 

16 Oct

Ethanol results and a slew of other solvents

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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15 Oct

Toluene

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.
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13 Oct

Frustration with recrystallization

Published by RyanPakula

Subject 

Request for Help

Last Wednesday I began some simple tests to try to find a good solvent for recrystallization, and here's some details and thoughts on what I've found so far.

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