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Author: Subject: Large alcohol recrystallization
EverythingAl2O3
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[*] posted on 28-12-2020 at 18:43
Large alcohol recrystallization


I'm planning on making these alcohols, but their boiling points are so high that my hot plate can't reach it and I cannot find information on the water azeotrope so steam distillation may take forever to get a significant amount.
I cannot find melting points for these specific molecules, but similarly sized 2-methyldecan-1-ol has a melting point of 11C. So maybe recrystallization could be an option? Would pure alcohol solvents, Ethanol-Water or Isopropanol-Water make a good recrystallization solvent? Or is there another solvent that works better for this?
Also I saw on OrgSyn that paraformaldehyde can be used polymerized for Grignard but at lower yields (40-50% for a reaction time of 75 minutes). Would longer reaction times help increase yield?
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[*] posted on 28-12-2020 at 20:11


Do you have a dean stark trap heavy return? then do a steam dist. Or set up the heavy return system that nurdrage built and run it till you have enough product. Everything has to form a tiny azeotrope with water, so it'll work eventually.
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Justin Blaise
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[*] posted on 28-12-2020 at 23:01


The longer reaction time for the Grignard may not increase yield, but it is unlikely to hurt the yield either. If monitoring the reaction isn't possible, I'd maybe let it go overnight.

For products with high boiling points, vacuum distillation is probably the way to go. While it is possible to crystallize low melting point solids, it's not easy and small amounts of impurities can depress your melting point enough that the compounds just don't crystallize even at temperatures well below their melting points. I find this to be the case with a lot of greasey, floppy compounds like the ones you want to make. I'd look into vacuum distillation for these compounds.
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[*] posted on 28-12-2020 at 23:48


Org. Syn. procedures have usually been optimized. The best of the best.

If longer reaction time would have increased yield, they would have cited a longer reaction time.

There might be a better procedure out there now, but at time of publication, their way...was probably the best way.

As for steam distillation. And/or re-crystallization. You will have to try it. Such things are not entirely predictable.

[Edited on 29-12-2020 by zed]

[Edited on 29-12-2020 by zed]
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EverythingAl2O3
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[*] posted on 29-12-2020 at 09:30



Quote:

Do you have a dean stark trap heavy return? then do a steam dist. Or set up the heavy return system that nurdrage built and run it till you have enough product. Everything has to form a tiny azeotrope with water, so it'll work eventually.

I do not have a dean stark trap yet which is why I wanted to try recrystallization first if it saved time over steam distillation
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[*] posted on 29-12-2020 at 11:02


Do you have the glass to make the nurdrage version?
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EverythingAl2O3
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[*] posted on 30-12-2020 at 20:10



Quote:

Do you have the glass to make the nurdrage version?

Yes. I'm gonna need to get a glass cutter to make it. I have been practicing glass working but having issues with cracking while cooling.
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