Fluorine acids

Fluorinated Acids. This class of compounds is characterized by the strength of the fluorocarbon acids, eg, CF COOH, approaching that of mineral acids. This property results from the strong inductive effect of fluorine and is markedly less when the fluorocarbon group is moved away from the carbonyl group. Generally, their reactions are similar to organic acids and they find apphcations, particularly trifluoroacetic acid [76-05-1] and its anhydride [407-25-0] as promotors in the preparation of esters and ketones and in nitration reactions. 

Because of thetr electron deficient nature, fluoroolefms are often nucleophihcally attacked by alcohols and alkoxides Ethers are commonly produced by these addition and addition-elimination reactions The wide availability of alcohols and fliioroolefins has established the generality of the nucleophilic addition reactions The mechanism of the addition reaction is generally believed to proceed by attack at a vinylic carbon to produce an intermediate fluorocarbanion as the rate-determining slow step The intermediate carbanion may react with a proton source to yield the saturated addition product Alternatively, the intermediate carbanion may, by elimination of P-halogen, lead to an unsaturated ether, often an enol or vinylic ether These addition and addition-elimination reactions have been previously reviewed [1, 2] The intermediate carbanions resulting from nucleophilic attack on fluoroolefins have also been trapped in situ with carbon dioxide, carbonates, and esters of fluorinated acids [3, 4, 5] (equations 1 and 2)... 

Monofluoroacetic acid offers little promise as a mosquito larvicide, but 2-ethylhexyl monofluoroacetate is a very powerful aphicide. The high toxicity of the fluorinated lower aliphatic acids and their esters to vertebrates probably precludes their use as insecticides except under highly controlled conditions. The toxicity of the fluorinated acids to the vertebrates is attributed to their interference with an enzyme system, but the possibility of finding one with a high specificity for insects is not excluded. 

Fluorinated acids and acid derivatives Fluorostearic acidic 9,10-Difluorostearic acid< Monofluoroundecanic acide Sodium monofluoroleate Methyl fluoroundecanate ... 

Some of the fluorinated acids are considerably more toxic to animals than to human beings.57 On the other hand, it has been shown that the impact of fluoroacetate-containing plants on fauna results in evolution of a marked tolerance to the poison.58 In the longer chain... 

Table 11. Toxicity Data of Fluorinated Acids and Derivatives...

Esters of carboxylic acids are resistant toward sulfur tetrafluoride up to 300 °C. However, in the presence of an excess of hydrogen fluoride, they react like the acids to give trifluoromethyl compounds [187,235] In contrast, esters of highly fluorinated acids or alcohols react with sulfur tetrafluonde in a hydrogen fluoride solution under mild conditions without cleavage of the ester bond and give products of the replacement of carbonyl oxygen by fluorine a,a-difluoroethers [235, 236, 237, 238] (equations 124 and 125). 

Bernett, M. K., and W. A. Zisman Wetting of low-energy solids by aqueous solutions of highly fluorinated acids and salts. J. Phys. Chem. 63, 1911 —1916 (1959). 

Recently fluorinated chains were also attached to amine based dendrimers, like PPI and poly(amido amine) (PAMAM), by means of ionic self assembly with semiperfluorinated alkanoic acids (Fig. 71, 216, 217). All dendrimer complexes 216 with perfluorinated alkanoic acids show SmA phases except the fifth generation dendrimer which shows a Colrec phase [378]. Also semiperfluorinated 4-alkoxybenzoic acids 217 [379] and mixed systems combining fluorinated and nonfluorinated alkanoic or benzoic acids (216, 217) have been reported [379-381]. In most cases layer structures (SmA) and for higher generation dendrimers also modulated SmA phases (Colrec phases) were observed. The layer thickness of the SmA phases of the mixed complexes 216 depends on the ratio of fluorinated and non-fluorinated acids, where smaller d values were observed for dendrimers with low Rp-content for Rp-rich dendrimers the more rigid Rp-chains provide... 

Essentially, TFE in gaseous state is polymerized via a free radical addition mechanism in aqueous medium with water-soluble free radical initiators, such as peroxy-disulfates, organic peroxides, or reduction-activation systems.15 The additives have to be selected very carefully since they may interfere with the polymerization. They may either inhibit the process or cause chain transfer that leads to inferior products. When producing aqueous dispersions, highly halogenated emulsifiers, such as fully fluorinated acids,16 are used. If the process requires normal emulsifiers, these have to be injected only after the polymerization has started.17 TFE polymerizes readily at moderate temperatures (40 to 80°C) (104 to 176°F) and moderate pressures (0.7 to 2.8 MPa) (102 to 406 psi). The reaction is extremely exothermic (the heat of polymerization is 41 kcal/mol). 

From 1952, Hauptschein et al. [23] studied the polycondensation of fluorinated acid diehlorides and diols according to the following reaction ... 

Borate esters of fluorinated alcohols, simply prepared by the free-radical addition of trialkyl borates to fluorinated alkenes, are cleaved by chlorine to yield fluorinated acid chlorides (equation 141)949. 

Oxygen acids are weaker than fluorine acids in view of the fact that in the first case the proton of a divalent ion, in the second case of a monovalent ion, must be set free. 

A number of different Lewis acids has been used in the past to initiate cationic polymerization of heterocyclic monomers. The strongest Lewis fluorine acids, as measured in the solution, on the pH scale by electrochemical titration are [32] ... 

Isocyanates of fluorinated compounds can readily be obtained either from trimethylsilyl isocyanate and, e.g. trifluoroacetyl chloride, with yields of isocyanate in the region of 64%. or more conveniently by Curtius degradation of fluorinated acid chlorides. ... 

For reasons of symmetry the resulting acids are identical when a symmetrically substituted alkcne is oxidized. For the preparation of short-chain fluorinated acids, such as trifluoroacetic acid. this method is more economical than the oxidation of an alkene with a terminal C = C bond (see Table 1). Oxidation of polyfluorinated dienes and polyenes gives fluorinated dicar-boxylic acids. 

The oxidation of fluoro compounds with potassium permanganate in an alkaline medium is of long standing. This reaction is a convenient method for the preparation of a-fluorinated carboxylic acids, particularly for the production of fluorochloroalkanecarboxylic and per-fluorinated acids. Carboxylic acids which have an a-hydrogen and -fluorine cannot be produced in this way because they eliminate hydrogen fluoride under the influence of alkali. ... 

The thermal decomposition of salts of fluorinated acids gives tw o different types of products. depending on the reaction conditions and the type of cation. When the decarboxylation of alkali and alkaline earth metal salts is carried out in the presence of proton donors, such as water, alcohol, aniline, pyridine or other basic solvents, the product of the reaction is a fluorocarbon hydride. This is a general procedure for the preparation of 1 /Z-perfluoroalkanes. ... 

The preparation of fluorinated acid anhydrides can be done by simple methods Phosphorus pentoxide removes a molecular equivalent of water from trifluoroacetic acid and tnfluoromethanesulfomc acid and forms the mixed anhydride [5J] (equation 53)... 

Moreover, hydrocarboxylation reactions have been expanded to include functionalized olefins as substrates, leading to arylpropionic acids [16], fluorinated acids [17], silylated esters [18], and y5-amino acids [19] as products (Structures 1-6). 

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