jtkelectroman
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Trifluoroacetic acid What to do with it?
Okay so I've got about 100mLs of it does anyone know of any cool compounds that can be made from it or how to use it to introduce trifluoromethyl
groups onto organic molecules. BTW I'm not planning on making any thing illeagle with it so if anyone has ideas of illeagle compounds that can be made
with it please don't share them.
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vulture
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It can be used as a non aqueous solvent. Or ofcourse as a strong acid which can be boiled off easily. The anhydride is interesting as a solvent
because of its low boiling point. IIRC it is used in the synthesis of some diformylpiperazine explosive.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Sandmeyer
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One use is in the Duff formylation... You can't introduce trifluoromethyl like that... I meen what I consider a 'cool compound' someone else might
consider a horrible compound, so what do you meen?
[Edited on 15-3-2007 by Sandmeyer]
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jtkelectroman
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Thalliation
Interesting info. You wouldn't happen to know if the anhydride can be made from it would you. By the way does anyone know if pyrolysis of the calcium
trifluoroacetate salt would yeild trifluoroacetone?
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jtkelectroman
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| Quote: | Originally posted by Sandmeyer
One use is in the Duff formylation... You can't introduce trifluoromethyl like that... I meen what I consider a 'cool compound' someone else might
consider a horrible compound, so what do you meen?
[Edited on 15-3-2007 by Sandmeyer] |
IF a chemical has interesting chemical properties then I consider it to be cool.
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jon
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well if you don't know you better axe somebody, but seriously you can alway send it to me if ya don't know what to do with it.
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Sauron
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The vapor of TFA is EXTREMELY irritating to the eyes in particular. Don't even consider opening that bottle outside of an efficient hood and while
wearing appropriate protection: gloves and goggles at the minimum.
BTW an illeagle is an unwell bird of prey.
I think you mean illegal. While we sometimes refer to lawyers as legal eagles, I' hate to mix them up any further and anyway they are more like
buzzards and other carrion eaters.
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jtkelectroman
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Ya the stuff is quite nasty I know that it has very low vapor pressure and outside of a fume hood the vapors become irritating shortly after opening a
bottle of TFA
| Quote: | Originally posted by Sauron
The vapor of TFA is EXTREMELY irritating to the eyes in particular. Don't even consider opening that bottle outside of an efficient hood and while
wearing appropriate protection: gloves and goggles at the minimum.
BTW an illeagle is an unwell bird of prey.
I think you mean illegal. While we sometimes refer to lawyers as legal eagles, I' hate to mix them up any further and anyway they are more like
buzzards and other carrion eaters. |
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Furch
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TFA is an excellent acid to make the peracid from. It's often considered the best peracid, together with para-chloroperbenzoic acid and perbenzoic
acid. These in turn can be used in e.g. the Bayer-Villiger oxidation to make ketones from alkenes, and esters from ethers.
However I seem to remember that the preparation of trifluoroperacetic acid begins with the anhydride and not the acid... However I don't see any
problems in making it from the acetyl chloride and acid.
I suppose you can make the acid chloride by refluxing with thionyl chloride and an acid scavenger. The only problem is that SOCl2 and the product
probably have very similar boiling points, thusly you have do destroy the excess SOCl2 by adding a more or less accurate amount of formic acid (IIRC).
[Edited on 16-3-2007 by Furch]
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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Klute
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You can make TFPeracetic acid from TFAA and H2O2 of suitable concentration, but it slowly decomposes to carbon dioxide and fluoroform.... If your
reaction proceeds quickly enough, it should be OK, but I don't really know HOW quick the decomposition proceeds... It also appears to be catalysed by
certain meatls salts such as Cu2+ salts... H2SO4 doesn't seem to either dimisih nor accelerate the decomposition...
TFPAA can also be used to oxidize pyridine derivatives to corresponding N-oxides, sulfides to sulfones,and other peracid reactions...
Furch, I'm pretty sure the Bayer/Villiger reaction is only the oxidation of an carbonyl to an ester/lactone and/or it's hydrolysis products... I've
never heard of peracid oxidation on alkenes (yielding epoxides or glycols, which can then be hydrolised to ketones) or on ethers being called
Bayer/Villiger oxidations; maybe you confused general peracid oxydation with the Bayer/Villger reaction? but feel free to prove me wrong otherwise.
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Furch
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Of course... But your hair splitting reasoning is the same as saying that a Grignard reagent on a ketone doesn't yield an alcohol - it yields an
alkoxide ion which upon acidification gives an alcohol.
And yes I was referring to the Bayer-Villiger rearrangement, which incidentally happens to be an oxidation and yields esters from
ethers.
The oxidation of an alkene to an epoxide by means of a peroxy acid is called the Prilezhaev oxidation (I looked it up in March's). This
epoxide can be hydrolyzed to a ketone in situ by means of treatment with a strong aqueous acid.
Thank you for pointing out my symantical errors however, I'll do my best not to let it happen again.
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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Nicodem
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| Quote: | Originally posted by Furch
And yes I was referring to the Bayer-Villiger rearrangement, which incidentally happens to be an oxidation and yields esters from
ethers. |
Please explain what kind of rearrangement you are talking about. Give an example and also explain how can an oxidation of ethers into esters involve
an rearrangement when the backbone does not change at all!
I never ever heard of the reaction that you talk about. I only know of the Bayer-Villiger oxidation of ketones to esters which indeed involves a
rearrangement, but has absolutely nothing to do with the transformation you talk about.
Edit: I take it you meant semantic and not "symantical", but I had the net impression that Klute did not care about the semantics but tried to correct
the erroneous statements in your post instead.
[Edited on by Nicodem]
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Klute
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Sorry, didn't mean to be looking for unsignifiant errors, I was just surprised to hear an oxidation of an alkene/ether called Bayer/Villiger.
PS:The only oxidation of ethers to esters I know of is by using ruthenium tretoxide or trichloroisocyanuric acid... does this oxidation proceed via
a Criegee adduct, as a BV on ketones?
PS2: just saw that nicodem replied before I finished. I would still be interested in the answer.
[Edited on 16-3-2007 by Klute]
[Edited on 16-3-2007 by Klute]
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Nicodem
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| Quote: | Originally posted by Klute
I was just surprised to hear an oxidation of an alkene/ether called Bayer/Villiger. |
Me too, and I was also surprised to read that the epoxide/glycol rearrangement is now called a hydrolysis of epoxides when there is nothing to
hydrolyze there. I could agree that the epoxide rearrangement is wrong name for a reaction where the only the heteroatoms arrangement changes But to
call it a hydrolysis?
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Klute
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Yes, that's wrong  the error came out because of the practical synthesis of
ketone from alkene, when the glycol/epoxide is refluxed in dilute H2SO4, i guess wrongly called "hydrolysis", because this is the same conditions when
you hydrolyse an ester.... Pinacol rearrangement would be the right name, no? my bad.
PS: I'll shut up next time
[Edited on 16-3-2007 by Klute]
[Edited on 16-3-2007 by Klute]
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Nicodem
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| Quote: | Originally posted by Klute
Pinacol rearrangement would be the right name, no? my bad.
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No. The pinacol rearrangement is mechanistically a completely different reaction. It involves the migration of an alkyl group from the side of a tertiary
alcohol to the neighboring carbocation (which on turn forms by the protonated –OH group leaving). Hence it is a true rearrangement, but it can only
happen on glycols/epoxides that have no neighboring hydrogen good enough for an efficient elimination.
Instead the glycol/epoxide rearrangement is not really a true rearrangement but it is just called this way. The first step involves the addition of a
proton (or other Lewis acid) on the oxygen of the epoxide or on one of the –OH of the glycol followed by the formation of the carbocation (by H2O
elimination in glycols). The carbocation finally stabilizes by proton elimination. The so formed enol tautomerizes to the ketone. Thus the crucial
difference is in how the intermediate carbocation stabilizes (alkyl migration vs. proton elimination).
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Klute
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Thanks for clearing that! So the reaction from a glycol with an available H to a ketone would actually be some kind of
mono-deshydratation/elimination...
And actually there is something to hydrolyse in the epoxide/glycol "rearrangement": if performic acid is used, the formed epoxides opens to an glycol
that then esterifies to a mono-formylglycol, which is then hydrolysed in dilute acid before the deshydrataion proceeds.. 
Just nagging, we could stay all night if I keep on like this, so I retire
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Furch
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I seem to have confused a couple of things with some other things... I hope noone tried to learn anything from that post :-}
That is the result of sleep depravation and too much caffeine... And some other things that I'm not particularly proud of 
Thanks for clearing the air however, Klute and Nicodem!
- Furch
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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