Perfluorocarboxylic acid fluorides

The products of the electrochemical perfluorination of aliphatic or cyclic ethers are the corresponding perfluorinated ethers. Byproducts are perfluorinated ethers with shorter carbon chains, perfluoroalkanes, perfluorocarboxylic acid fluorides and oxygen difluoride. Cyclic perfluorinated ethers can be produced by electrochemical fluorination of alcohols,32 aliphatic carboxylic acids33 or of their acid halides34 containing not less than four carbon atoms in the chain. 

Like perfluorocarboxylic acid fluorides, perfluoroalkyl chlorosulfonates react with 2-aminophenols, 2-aminothiophenols, and 1,2-diaminobenzene to give A -acylated products. On subsequent heating ring closure occurs with formation of 2-perfluoroalkyl-substituted benzoxazoles, benzothiazoles, and benzimidazoles [90JFC(49)197] (Scheme 44). 

The yield of a perfluorocarboxylic acid fluoride is higher when a carboxylic acid chloride or fluoride is fluorinated instead of the carboxylic acid or its anhydride [48,49]. For example, acetic acid, acetic acid anhydride, and acetyl fluoride give trifluoroacetyl fluoride in 17%, 32%, and 76% yields, respectively [32,49] ... 

The perfluorocarboxylic acid fluorides can be converted to perfluorocarboxylic acids, esters, amides, or other intermediates for surfactants (Fig. 2.2). Hydrolysis of the acid fluoride yields the carboxylic acid (I) or its salt (II). Alcohols form esters (HI), which can be hydrogenated to an alcohol (IV), an intermediate for nonionic surfactants. The reaction of the acid fluoride with an amine [e.g., NH2C3H6N(CH3)2] yields an intermediate (V) for an amine salt (VI), a cationic... 

Electrochemical fluorination of carboxylic acids in anhydrous hydrofluoric acid was invented by Simons [106,107]. A process developed by the 3M Co. [108,109] yields perfluorocarboxylic acid fluoride, which can be converted to esters, amides, or other intermediates for the production of repellents ... 

If esters arc perfluorinated the main products are perfluoroalkanes or perfluoroacyl fluorides byproducts are carbon dioxide and oxygen difluoride. The acyl and the alkyl groups in the ester give perfluorocarboxylic acids.41 A comparison of the results obtained from butyl acetate and ethyl butyrate, and from butyl propionate and propyl butyrate, indicates that perfluoro-butanoic acid is obtained in better yield from ethyl and propyl butyrate than from butyl acetate and butyl propionate. Thus, perfluorocarboxylic acids are formed more readily from the acyl than from the alkyl group of the ester. 

The effluent gases from the cell were passed over NaF pellets and then bubbled through two consecutive bottles containing H20 (for collection of the perfluorocarboxylic acids which were formed as a result of the hydrolysis of the pcrfluoroalkanoyl fluorides). The gaseous products which did not react with H20 were led into an alkaline solution of K2S03, and finally collected in traps immersed in liquid N2. Products pcrfluoro(2.4-dimethyltetrahydrofuran) (20%), perfluoi o(2-methyltetrahydropyran) (5.5%), perfluoro(3-methyltetrahydropyran) (10%) and perfiuoro(2-methylpentanoyl fluoride) (7%). 

Enolphosphate phosphonates derived from perfluoroalkanoylphosphonates have a number of synthetic uses. Reactions of such compounds with nucleophiles such as amines or alcohols in the presence of catalytic amounts of tetrabutylammonium fluoride (tbaf) gave a,j5-unsaturated perfluorocarboxylic acid derivatives, presumably via a ketene type intermediate (equation 94) When a primary amine was employed as the nucleophile a,j -unsaturated amides were formed, which could be converted into fluorinated pyrimidi-nones by treatment with urea. On the other hand, butylcopper(I) reagent reduces such... 

In the past years, elucidation of transformation products of per- and polyfluorinated compounds (PFC) has been a task frequently approached by analytical chemists. It has been estimated that biotransformation contributes to approximately 0.1-5% with respect to perfluorocarboxylic acid (PFCA) historical global emissions [1]. For perfluorooctanesulfonyl fluoride (POSF)-based compounds such as perfluorooctane sulfonic acid (PFOS), biotransformation products probably affect environmental burden marginally, although no distinct estimations have been made so far [2]. 

Some oxidation systems have been reported to decompose perfluorocarboxylic acids (PFA) and the corresponding sulfonic acids (PFS) at bench scale. The primary products are PFAs with shorter chain length, CO2 and fluoride. The reaction is often proposed to be initiated by electron transfer from the ionic head group to an appropriate electron acceptor. In that regard, especially sulfate radical anions and electrolysis using boron-doped diamond electrodes have been reported to degrade PFA respectively PFS. 

Shinohara " prepared perfluorocarboxylic acids by oxidative filuorination of poly(vinylidene fluoride) followed by hydrolysis, as in Scheme 12. Such compounds are more acidic than their non-fluorinated equivalents and can be used to prepare cation exchangers. 

Terpolymerization (2, 3, 4, 6, 8, 33). Membranes containing both perfluorocarboxylic and sulfonic acid groups can be prepared by hydrolyzing a film formed by terpolymerization of TFE and two PVEX monomers containing a carboxylic ester group and sulfonyl fluoride group. 

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