The thermal decomposition of trifluoroacetic acid

Veröffentlicht 2023-07-25 07:30:45

The major products of thermal decomposition of trifluoroacetic acid at 300–390° in silica and mild-steel vessels are carbon dioxide, difluoromethyl trifluoroacetate, carbon monoxide, and trifluoroacetyl fluoride. Decomposition is believed to proceed through elimination of hydrogen fluoride, followed by the formation of difluoromethylene (CF2), which largely adds to trifluoroacetic acid to give the difluoromethyl ester. Reaction orders for decomposition and formation of products are fractional and increase with temperature, suggesting that the decomposition is partly heterogeneous.

The reactions of trifluoroacetic acid are centered on its carboxyl group. The trifluromethyl group is of the most stable structures known, being inert towards practically all oxidizing, reducing, and hydrolyzing conditions. Although a strong organic acid, trifluoroacetic acid is considerably weaker than strong inorganic acids. The use of trifluoroacetic acid as an olefin hydration promoter permits the synthesis of alcohols from olefins which are polymerized, oxidized, or otherwise decomposed by sulfuric acid. A wide range of reactions are promoted by trifluroacetic acid including esterifications, condensations, and oxidations. Its advantages over the usual acid catalysts are smoother reaction and less decomposition. TFA also offers easy handling and recovery in these applications.

Trifluoroacetic acid (TFA) is one of a group of thousands of substances collectively called poly- and per-fluorinated substances (PFAS), which are highly persistent in the environment. As a group they are being considered under a risk management options analysis under UK chemical regulation (UK REACH). The Environment Agency (EA) also considers TFA as part of its priority and early warning system for chemicals.
We are aware of some concerns raised about TFA and trifluoroacetate in relation to the breakdown of certain refrigerants, in particular hydrofluoro-olefins (HFOs). HFOs are used increasingly as replacements for hydrofluorocarbons (HFCs) due to their much lower Global Warming Potential.