Perfluorinated carboxylated

However, it is known that carboxylic perfluorinated acids, in particular perfluorooctanoic acid, accumulate in the living organisms and are environmentally persistent [68],... 

Ltd.) and the perfluorinated membranes produced by the Asahi Chemical Industry Company (18). Recently, carboxylate perfluorinated materials have been available from DuPont Company. 

Structure of Sulfonated and Carboxylated Perfluorinated Ionomer Membranes... 

The combinations of these perfluorovinyl ethers with tetrafluoroethylene have prompted the commercialization of various fluoropolymers of industrial importance, such as Kalrez perfluoroelastomer, Teflon PFA thermoprocessable perfluororesin without deteriorating the excellent properties of PTFE. Nafion and Flemion are sulfonated and carboxylated perfluorinated ion exchange membranes, respectively. 

SouKe Hashimoto, T. et al., Structure of sulfonated and carboxylated perfluorinated ionomer membranes, in Peifluorinated Ionomer Membranes, American Chemical Society, Vol. 180, 1982, pp. 217-248. 

Cm ORINE OXYGEN ACIDS AND SALTS - DICm ORINE MONOXIDE, HYPOCm OROUS ACID, AND HYPOCm ORITES] (Vol 5) Perfluorinated carboxylic acids... 

Perfluorinated carboxylic acids are corrosive liquids or solids. The acids are completely ionized in water. The acids are of commercial significance because of their unusual acid strength, chemical stabiUty, high surface activity, and salt solubiUty characteristics. The perfluoroaLkyl acids with six carbons or less are hquids the higher analogues are soHds (Table 1). 

During electrochemical fluorination retention of important functional groups or atoms in molecules is essential. Acyl fluorides and chlorides, but not carboxylic acids and anhydrides (which decarboxylate), survive perfluorination to the perfluorinated acid fluorides, albeit with some cyclization in longer chain (>C4) species [73]. Electrochemical fluorination of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluorination of octanoyl chloride results in perfluorinated cyclic ethers as well as perfluorinated octanoyl fluonde. Cyclization decreases as initial substrate concentration increases and has been linked to hydrogen-bonded onium polycations [73]. Cyclization is a common phenomenon involving longer (>C4) and branched chains. a-Alkyl-substituted carboxylic acid chlorides, fluorides, and methyl esters produce both the perfluorinated cyclic five- and six-membered ring ethers as well as the perfluorinated acid... 

Hexafluoroacetone and certain perfluorinated or partially fluorinated ketones, aldehydes, and imines react with a-functionalized carboxylic acids (e.g., a-amino, a-At-methylamino [S3, 84], a-hydroxy [S5], and a-mercapto [Sd] acids) to give five-membered heterocyclic systems (equation 13). 

Carboxylic acids with a halide, hydroxy or amino group in the a-position form no dimers (Table 2, No. 11), except when two or three fluorine atoms are pr ent there (Table 2, No. 12). A large amount of work has been devoted to the coupling of fluoro-carboxylic acids (Table 2, Nos. 13-16) due to interesting properties of the produced fluorohydrocarbons. By statistical analysis optimal conditions for Kolbe ela trolysis of perfluorinated acids have been calculated [135]. 

In this section, we will neglect the crystal structures of the mesogenic perfluorinated phenyl benzoates [23-27], benzoic acids [6, 28-31], cinnamic acids [7, 32, 33], dicarboxylic acids [34, 35], and cinnamate compounds [8, 36-40]. The single crystal X-ray analyses of chiral mesogenic carboxylates are described in Sect. 6. 

Ellis DA, JW Martin, AO De Silva, SA Mabury, MD Hurley, MPS Andersen, TJ Wallington (2004) Degradation of fluorotelomer alcohols a likely atmospheric source of perfluorinated carboxylic acids. Environ Sci Technol 38 3316-3321. 

Other anionic surfactant types include the alkylisethionates (9.22), N-acylsarcosides (9.23), N-acyltaurides (9.24) and perfluorinated carboxylates, sulphonates (e.g. 9.25), sulphates and phosphates [13]. 

Electrofluorination of aliphatic carboxylic and sulfonic acid chlorides or fluorides to perfluorinated products [31]. 

At the end of the 1990s statistics show that the non-ionic surfactants achieved the highest growth in production rates world-wide, though anionic surfactants (anionics) maintained the dominant position in the surfactant market. Today they are produced in a larger variety by the petrochemical industry than all other types of surfactants. Their production spectrum covers alkyl sulfates (ASs), secondary alkane sulfonates (SASs) and aryl sulfonates and carboxylates via derivatives of partly fluorinated or perfluorinated alkyl surfactants to compounds with an alkylpolyglycolether substructure combined with an anionic moiety such as alkylether sulfates (AESs), phosphates, phosphonates or carboxylates. 

Partly fluorinated or perfluorinated sulfonic and carboxylic acids are compounds with excellent surface activity combined with an extreme stability against chemical or physico-chemical attacks as also described for non-ionic fluorine containing surfactant compounds. The anionic surfactants are shown with their structural formulae in Fig. 2.11.24(1)—(III). A selected ESI-FIA-MS(-) spectrum of a partly fluorinated surfactant (CF3-(CF2)4-(CH2)8-S03H, m/z 461) is presented in Fig. 2.11.25. The FIA spectrum also contains ions of the by-products CF3-(CF2)2-(CH2)8-S03H (m/z 361) and CF3-(CF2)3-(CH2)8-S03H (m/z 411). 

Fig. 2.11.24. General structural formulae of (I) perfluorinated alkylsulfonic acid, (II) partly fluorinated alkylsulfonic acid, and (III) perfluorinated carboxylic acid.

Aldehydes may be converted to carboxylic acids using Ni(acac)2 immobilized in [bmim][PF,5], with oxygen as the oxidant, as shown in Scheme 9.14 [27], A similar reaction has also been performed using perfluorinated solvents, and it was found that there was little difference between the two systems [28], However, the Ni(acac)2 catalyst could not be used directly in the fluorous solvent and therefore the 1,3-diketonate was modified with long perfluorinated chains prior to use to ensure solubility. 

A complex reaction between perfluoro 2-methylpent-2-ene and carboxylic acids in the presence of potassium carbonate and Aliquat produces the acid fluoride, as the major product, with variable amounts of the 3-acyloxy perfluorinated alkene [37]. The procedure has little value for the synthesis of either compound. 

The attempt to use these salts originated from the hope that their dissociation constants would be high even in low dielectric media, and the organic nature of perfluorinated alkyls would always assist the solubility of the salts in nonaqueous solvents. Because of the requirement for electrochemical stability, lithium carboxylates (RF-C02Li, where Rp- = perfluorinated alkyls) are excluded from consideration, because their oxidation still occurs at - 3.5 V vs lithium, which is similar to the cases of their non-fluorinated counterparts. Obviously, the electron-withdrawing groups do not stabilize the carboxylate anions sufficiently to alter their oxidative stability. 

A lesser number of papers have appeared regarding the carboxylate version of Nafion, and the works of Yeager et al., - Seko et al., and Perusich et al. ° are of special note. Nafion-like carboxylate materials have also been reported." These similar materials will not be discussed here, as the exclusive emphasis is on the stronger-acid sulfonated versions because this critical review is within a collection of articles in which perfluorinated ionomers are considered within the context of fuel cells. 

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