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Harmless
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Purifying apiole and its isomer without fractional vacuum distillation
The other isomer is that found in dill oil, dillapiole.
The bp's and mp's are approximate, I can only recall the ballpark of where they were when I looked them up.
A few attempts have been made to isolate first dillapiole from its oil. The major components of the oil are limonene (bp = 175) carvone (bp = 240, mp
= 30) and dillapiole (bp = 290, mp = 30).
One might guess that limonene and carvone could be boiled off at atmospheric pressure to yield a residue of mainly dillapiole. The oil had been placed
in a flat bottom flask and put on a table top burner. The thermometer placed into the oil could only read up to 170 C. At about 150 C some bubbling
began, and at probably 180 C the oil began to smoke. The temperature had run above probably 200 C and the smoking continued. What was left was a
disgusting black syrup.
Another attempt: A new portion of oil had been placed in a freezer around -20 C. Nothing had crystallized out at 24 hours. An equal volume quantity of
hexane was added to the oil and put back in the freezer. 24 hours later a tan semi-solid layer forms on the bottom of the flask. Decanting led to two
layers, both of which were liquid at room temperature. The solid layer grew much darker upon coming to RT.
Both layers floated in water. Carvone should float, dillapiole should sink.
A third attempt has been tried where a saturated solution of sodium metabisulfite with an equal volume of ethanol was added to the oil. Nothing
precipitated out.
It should be said that this had been attempted but with acetone as a test, and it seemed only an excess of acetone caused precipitation.
Finally, not much has been tried with apiole, but it does not precipitate out at -20 C. Internet sources have claimed apiole can sometime even
precipitate out at room temperature.
What would you conclude from any of these trials and how might one continue? Perhaps a simple vacuum "distillation" using a buchner funnel may be
attempted to remove limonene and carvone from the dillapiole. One wonders how a vacuum pump would respond to carvone and limonene though.
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ScienceSquirrel
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Quite frankly the only way you are going to do this is with either fractional distillation under vacuum or column chromatography.
The dillapiole can be a sizeable or fairly minor component of the oil depending on it's source. I would say the chance of getting worthwhile
separations with improvised gear is small.
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The oil in question is likely not too minor of a component. It had been stated that the oil contained limonene, carvone, and dillapiole. Listed as
being present in trace amounts were phellandrene, dihydrocarvone, and terpinene.
Dillapiole has the highest bp and by a 40 or 50 C margin. Since the oil appears to not take kindly to the heat, perhaps throwing it into a stoppered
buchner funnel attached to a pool pump can safely remove the more volatile components.
This will not work for the oil containing apiole, since that also contains heavier allylbenzenes like myristicin.
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Bot0nist
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Got something needing aborted? Sorry, just joking of course.
When you said you ended up with a black syrup, do you think the terpenoids reacted or that the dillapiole decomposed due to heat? Maybe trying again
with a little vacuum and a good thermometer would help.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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ScienceSquirrel
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You really need some pure dillapiole that you can use as a standard as you try and do the purification or a TLC Rf in a known solvent mixture to
identify dillapiole in your material.
You need a reference point so that you can see how pure your material is and devise a purification method.
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Ephoton
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dillapiole in dill seed oil is not realy that high a content.
the first fraction will smell like jaffers very nice.
the last fraction must be distilled under vac as it burns very easily.
the cleaner the apiol is the less smell it will have.
the isomerisation of this fraction and then distillation there of is even harder as its boiling point
is even higher.
but then again if your thinking of oxidising this alkene you will more than likely want to distill it for purity.
the ketone will have an even higher boiling point than the alkene.
apiols need good vac and good seals on glass.
you can distill to around 180C with out the vac to remove some impurities from your apiol.
[Edited on 12-4-2011 by Ephoton]
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Ephoton
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another approch would be to distill the first fraction with out vacuum too 180C then
use steam to remove the carvone from the apiol.
http://en.wikipedia.org/wiki/Carvone
the laevo-form from the oils containing it, by first forming its addition compound with hydrogen sulfide, decomposing this by potassium hydroxide in
ethanol, and distilling the product in a current of steam.
It may be that you can steam the carvone away from the apiol 
you should be able to tell how close you are to pure apiol in water by stopping the
stirrer and distillation and seeing if the apiol has dropped to the bottom of the flask.
even pure I found it quite hard to get dill apiol to crystalise (though I have had
some crystalise)
[Edited on 12-4-2011 by Ephoton]
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postart
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There is a lot of good suggestions here but a $3-400 investment in vaccume distillator sounds undeniably practicle for this application. Also keep in
mind the geographic orgin of said oil as constituents can vary greatly.
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Nicodem
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Thread Moved
12-4-2011 at 09:22 |
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