Yorty2040 - 3-6-2024 at 14:27
So I'm trying to find a method of synthesizing trifluoroacetic anhydride.
My initial plan was to convert anhydrous acetic acid to the alpha-trichloro derivative via phosphorus trichloride and chlorine (a
Hell–Volhard–Zelinsky halogenation), then convert the trichloro to the trifluoro via antimony trifluoride and chlorine (Swarts fluorination), then
dehydrating the resulting trifluoroacetic acid with P2O5, but the antimony trifluoride seems difficult to get or make.
Or perhaps one could use bromine instead of chlorine in the HVZ reaction and sodium fluoride instead of antimony trifluoride for a simple Sn2 to
create the trifluoroacetic acid?
Does anyone have any other ideas regarding synthesis or sourcing?
[Edited on 4-6-2024 by Yorty2040]
j_sum1 - 3-6-2024 at 14:33
Of all the things in this reaction scheme that would be difficult, I would not have assumed it would be SbF3.
Rather you than me. This seems scary on so many levels.
Yorty2040 - 3-6-2024 at 16:42
If there were a different pathway I'd take that. The one I laid out seems like it would take me years to figure out, if I could get it going at all.
Organofluorine compounds seem like a PITA across the board.
Perhaps if I could find an old fire extinguisher with Halon 1301 (bromotrifluoromethane) and react it with an alkali cyanide dissolved in something
organic, then hydrolyze the nitrile to the carboxylic acid, isolate it, then dehydrate the acid with P2O5...
[Edited on 4-6-2024 by Yorty2040]
charley1957 - 4-6-2024 at 03:26
Old Halon fire extinguishers are still available. I recently called the local fire extinguisher inspector/refiller and asked if he had any CO2 fire
extinguishers that had not been claimed after filling. He gave me a CO2 extinguisher and a Halon extinguisher. So you might try going that route.
Jenks - 4-6-2024 at 05:02
Unless the point here is the challenge, I think if I were needing this, it would seem like the perfect excuse to finally line up an order with
Mario840 or someone similar, and leave my synthesizing challenges for a non-commercial product.
dettoo456 - 4-6-2024 at 05:37
Yea, preparing acetic anhydride (or any anhydrous acid at that) is a headache in its own right, not to mention the fact that the whole process would
end up being many times more expensive than just buying the TFAA itself.
TFA is also a known environmental pollutant; almost as bad as some PFAs. So unless you really need it, I’d try to find more interesting and less
toxic syntheses.
It’s entirely up to you though of course.
https://doi.org/10.1080/10807039991289644 (this doc paints TFA as a low-to-no concern chemical but literally half of the authors work for chemical
companies like DuPont, Solvay, ICI, Arkema, Daikin, etc and it’s funded by a Fluorocarbon acceptance group)
https://doi.org/10.1021/es047975u
https://doi.org/10.1016/j.foodchem.2021.129304
[Edited on 4-6-2024 by dettoo456]
clearly_not_atara - 4-6-2024 at 09:10
You can do the fluorination with silver fluoride. It's quite exothermic. But do keep in mind the warnings offered by everyone else regarding the
dangers of this procedure and the environmental hazard posed by TFA.
An alternative approach might involve the degradation of the commercial solvent parachlorobenzotrifluoride (Oxsol 100), which should give TFA upon
vigorous oxidation. This route could be a little safer. I hypothesize that an SNAr Cl -> OH with sodium hydroxide should be possible and open the
door to various phenol degradations.
Still another possibility is the oxidation of the HFO refrigerants.