The Vespiary
The Hive => Methods Discourse => Topic started by: locrian on December 05, 2001, 06:59:00 PM
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Swinl vac. refluxed 600mL of safrole with 10g NaOH overnight. It refluxed at 120C. The rxn. should have been completely anhydrous, but the reflux under vac. is supposed to take care of any water that may be in there. However, how does swinl know whether or not the isomerization was a success. It's water white clear. Swinl added 125mL of Acetone to 73 mL of this isosafrole (assuming it WAS isomerized). Then, this mixture was dripped into 458 mL of Peracetic acid. It was dripped slowly because the whole thing is supposed to be exothermic, right? However, it didn't seem exothermic. It was in an ice bath and the temp rose from about 7C to 9C, although in my compilation of hive posts, it says to make sure the reaction doesn't go above 40C as if the thing was going to get hot very easily and quickly. This doesn't mean that the isomerization process failed does it? I don't think so, but I just want to be sure before swinl goes and wastes a bunch of time and chem's.
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Distill the isosafrole! After converting safrole to isosafrole, the oil should be a dark almost opaque brownish black (using KOH). Yeah, the peracetic reaction isn't very exothermic, but it will boil DCM without external cooling. (or if you're using acetone, you'll note that is noticeably warms up)
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I'm sorry, swinl did distill the isosafrole, forget to mention that. It was a "dark almost opaque brownish black," with hints of dark red/orange in it before swinl distilled it. Is this the sign of success?
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So, should/could one use DCM in lieu of acetone in a peracetic (ep)oxidation? goiterjoe didn't have success, though he also used sodium acetate to buffer.
Any claification would be greatly appreciated,
PB
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There's nothing you can tell by colour changes and mere looking at crude products.
Isosafrole smells different than safrole, that is an easy way to distinguish the two.
Also, you shouldn't start cooling until the reaction heats up, and you shouldn't cool it too much, now that you did it anyway stir it for the required time without cooling, but observe the temp so it will not heat up too much.
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I've found that for most of the reactions done here, if you don't see a change (ie no heat released, no color change)... that is indicitive of no reaction taking place. Hg/Al, isomerization, peracids, gassing, etc, etc.. they all involve some sort of observable change in the reactants, if you're not seeing that, then no reaction has taken place. I'll agree with you that the opposite does not hold true (ie, just because you see a change, doesn't mean the reaction in question has taken place)
This boils down to:
1. if locrain's crude isosafrole was water white clear, like his starting safrole... that the isomerization was a failure.
2. if locrain did not observe something of a temperature increase and/or a color change from the peracetic, that the peracetic didn't work either.
(no offense intended to anyone! I don't intend to come off like a jerk on posts like this...)
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SWIM never found out one way or the other about the success of his reaction. Everything seemed to go fine, but the oil was relocated shortly thereafter. either way, DCM should actually work better than acetone, since it boils at a lower temperature and won't form acetone peroxide as a byproduct.
Sed quis custodiet ipsos custodes?
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> 1. if locrain's crude isosafrole was water white clear, like his
> starting safrole... that the isomerization was a failure.
isosafrole doesn't crystalize like safrole, correct? test it by dropping a seed crystal into cool isosafrole.
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"Also, you shouldn't start cooling until the reaction heats up, and you shouldn't cool it too much, now that you did it anyway stir it for the required time without cooling, but observe the temp so it will not heat up too much. "
Osmium, I did the normal performicacid procedure. Cooled with 17 degrees water, dripped my acetone/isosafrole mixture and temp rised to 30 at the higest, than began to drop to 22 (what was my cooling water's temp now. Did I cool it too much now? Reviews says colour has to change from orange to deep red, but mine turned from light orange to light red. Could this be good anyway?
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Check the bp by chance? should be higher than safrole
Why waste the chems or time with NaOH its a useless method compared to KOH.
Ever hear of the modified performic?
GODISNOWHERE