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The Hive => Chemistry Discourse => Topic started by: zooligan on November 19, 2001, 03:21:00 AM

Title: 3,4,5-TMNS recrystallization confusion
Post by: zooligan on November 19, 2001, 03:21:00 AM: O.K. One ref says "Don't attempt recrystallisation of nitroethenes from a boiling solvent - this will cause decomposition, significantly reduce yields, and you won't be able to get clean product."

Other refs say you recrystallize from MeOH, EtOH, or GAA.

What gives? Which is correct?

What should clean 3,4,5-TMNS look like? Is there definite crystalline structure?

Any help greatly appreciated!

z
"And if we don't get some cool rules ourselves, pronto, then we'll just be bogus too!"
Title: Re: 3,4,5-TMNS recrystallization confusion
Post by: Dr_Sister on November 19, 2001, 05:32:00 AM: it's true, boiling your nitro in a solvent with a bp of 78 is going to result in some decomposition. Try boiling the solvent by itself and then add it to a second container containing nitro. the temp falls off dramatically. As far a what solvent is used, what do you have? you have some flexibility here.
7.10.01
Title: Re: 3,4,5-TMNS recrystallization confusion
Post by: zooligan on November 19, 2001, 05:51:00 AM: MeOH, IpOH, tol, acetone, GAA.

Any idea what the rextallized compound should look like? Similiar to 2,4,5-TMNS I assume (translucent deep yellow needle-like xtals)...

z
"And if we don't get some cool rules ourselves, pronto, then we'll just be bogus too!"
Title: Re: 3,4,5-TMNS recrystallization confusion
Post by: Antibody2 on November 19, 2001, 06:12:00 AM: MeOH has the lowest Bp, if you want to be safe, my preference is 99% IPA.

I understood nitro crystals resulting from condensation rxns are much denser than crystals produced by pseudonitration.

Nother thing that can help, is to cool recrystallization solvent very slowly to avoid the product oiling out, which IMHO is the biggest snafu of recrystallizations besides using too much solvent.
"All those memories lost like rain..."
Title: Re: 3,4,5-TMNS recrystallization confusion
Post by: zooligan on November 19, 2001, 07:00:00 PM: O.K. Perhaps soon pictures will be posted somewhere for visual confirmation.

z

"And if we don't get some cool rules ourselves, pronto, then we'll just be bogus too!"
Title: Re: 3,4,5-TMNS recrystallization confusion
Post by: hest on November 20, 2001, 12:54:00 AM: Its not a problem to rextalise 3,4,5-tmns from (m)ethanol.
Its looks like nice yellow xtals. but iff you wants to bee sure take a mp.
Title: Re: 3,4,5-TMNS recrystallization confusion
Post by: uemura on November 20, 2001, 06:55:00 AM: z,
Slotta, Ber. 1933 recristallized the nitro-styrene from EtOH. 1 part NS, 7 parts EtOH. mp 120-121 DegC giving 'strong yellow plates'.
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