Perfluoroalkyl 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). 

The perfluoroarylcopper reagents react with perfluoroalkylated acid fluorides to give ketones in excellent yields. Solvent, type of organometallic reagent,... 

C. Lau, J.L. Butenhoff, J.M. Rogers, The developmental toxicity of perfluoroalkyl acids and their derivatives, Toxicol. Appl. Pharmacol. 198 (2004) 231-241. 

Perfluoroalkyl acids (PFAs) are synthetic, perfluorinated, straight- or bran-ched-chain organic acids characterized by a carboxylate or sulfonate moiety [1]. PFAs are manufactured directly but can also be formed through transformation of many precursor molecules containing a perfluoroalkyl moiety [2], These include fluorotelomer alcohols (FTOHs) and perfluoroalkyl-sulfonamides (Table 1, Fig. 1), however, others likely exist. Collectively, this family of chemicals including PFAs and their polyfluorinated precursors will be referred to in this document as perfluoroalkyl substances (PFSs). 

Fig. 1 Example structures of perfluoroalkyl acids (PFAs) and some of their precursor...

Perfluoroalkyl acids (PFAs) Acids of fluoropolymer, rust/oil/... 

Castro et al. 44) found that the order of reactivity of various halides in coupling reactions with ethynylcopper compounds in DMF is ArSX, ArX > RCOX ArCHaX, RCH=CHCH2X, ArCOCHaX > RCH= CHX, Alkyl-X. A somewhat different order is observed for the reactivity of some organic halides towards perhaloarylcopper reagents in THF (97, 147) Allyl Aryl > Alkyl and perfluoroaryl, perfluoro-vinyl > aryl > perfluoroalkyl. Acid halides were also far more reactive than aryl iodides in ethereal solvents 146). The ease of halide displacement is I > Br > Cl. 

The natural development of the study of this class of compounds has been the synthesis of protic ILs. In this context, a series of 18 samples were prepared by appropriately mixing acid and basic building blocks (Figure 17). By using di- or monocarboxyhc perfluoroalkylic acids, in combination with 1,2,4-oxadiazoles functionalized with either two pyridines or one pyridine and a fluorinated chain, it is possible to obtain symmetric and nonsymmetric fluorous architectures, respectively (2012PCP14306). Many... 

Polyfluorinated compounds comprise hundreds of chemicals characterized by hydrophobic linear alkyl chains partially or fully fluorinated (as the perfluorinated compounds [PFCs]) and containing different functional groups. Polyfluorinated compounds include perfluoroalkyl sulfonamides (PFASAs), fluorotelomer alcohols (FTOHs), polyfluorinated alkyl phosphates (PFAPs), fluorotelomer unsaturated carboxylic acids (FTUCAs), perfluoroalkyl acids (PFAAs), and their salts. The most common PFAAs are perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFASs). In particular, PFASs contain one or more fluorinated alkyl chains bonded to a polar head, which at neutral pH can be charged (anionic, cationic, and amphiphilic surfactants) or noncharged (nonionic surfactants). 

Abstract Fluorinated surfactants have been conunercially available since the 1950s. The first available were perfluoroalkyl sulfonic acids. The unique properties e.g., surface tension lowering in aqueous systems, high chemical and thermal stability of these acids and their derivatives when used at low concentrations resulted in their widespread use in industrial processes and consumer uses. The most common commercially produced peifluorinated surfactants are the perfluoroalkyl acids. 

Subsequently, additional conunercial processes were developed for synthesis of a range of per- and poly-fluorinated surfactants whose unique properties make them largely irreplaceable in many applications. The widespread use and disposal and the high stability of the perfluoroalkyl acids, which do not breakdown readily either abiotically or biotically in the environment, has resulted in widespread presence of PFAAs in the environment. This caused commercial production to shift toward short chain alternatives and new fluorinated moieties such as the per- and poly-fluorinated ethers. Clearly, there remains a need for fluorinated surfactants in many industries to obtain the beneficial performance properties of these substances that cannot be achieved with other types of surfactants. 

Separating and joining the hydrophobic/oleophobic tail and the hydrophilic group of the fluorinated surfactant is the critical organic linking group, often called the spacer [2-6]. Perfluoroalkyl acid (PFAA) surfactants such as perfluoroalkyl... 

Valsecchi, S. Polesello, S., The search of sources of perfluoroalkyl acids (PFAAs) in Northern Italian waters. In SETAC 19th annual meeting, Goleborg, 2009 Poster presentation abstract book, p. 129... 

M., and Mueller, J.E. 2011. Removal of PFOS, PFOA and other perfluoroalkyl acids at water reclamation plants in South East Queensland Australia. 

N. Yu, W. Shi, B. Zhang, G. Su, J. Feng, X. Zhang, S. Wei and H. Yu, Occurrence of perfluoroalkyl acids including perfluorooctane sulfonate isomers in Huai River Basin and Taihu Lake in Jiangsu Province, China, Environ. Sci. Technol. 47, 710-717(2013). 

The polarity of POPs does not necessarily correlate with these properties nor are all POPs nonreactive. Compounds range from highly nonpolar (e.g., PAHs) to ionic (e.g., perfluoroalkyl acids, PFAAs) and may be subject to reactions in the environment and in biota these transformation products may also meet the criteria for POPs. The biotransformation of xenobiotic compounds may involve, for example, hydrolysis, oxidation, or adduct formation reactions that increase the polarity of the metabolites to promote excretion. Other reaction processes occur in the environment (e.g., oxidation, photolysis) that transform the compounds to more polar forms. Because of the polarity of these transformation products, liquid chromatography is often better suited to their analysis than gas chromatography. Transformation products of POPs may exhibit similar or even greater toxicity than the parent compounds, and for these reasons, considerable interest exists in the measurement of POPs and their transformation products. 

Wolf CJ, Schmid JE, Lau C et al (2012) Activation of mouse and human peroxisome proliferator-activated receptor-alpha (PPAR alpha) by perfluoroalkyl acids (PFAAs) Further investigation of C4-C12 compounds. Reprod Toxicol 33(4) 546-551 Wolf CJ, Zehr RD, Schmid JE et al (2010) Developmental effects of perfluorononanoic acid in the mouse are dependent on peroxisome proliferator-activated receptor-alpha. PPAR Res 2010 1-11... 

Perfluoroalkylated fatty acid 6-esters of sucrose and aa-trehalose were prepared by a reaction of sucrose or a,a-trehalose with a perfluoroalkylated acid, Rf(CH2)rtCOOH (Rf = C4F9, C6F 3, or CgFi7, n = 2, 4, 10) in the presence of triphenylphosphine and diisopropyl azodicarboxylate in j/V,iV-dimethylformamide [262]. The surfactants were used to prepare fluorochemical emulsions intended as intravascular oxygen carriers (see Section 10.4). 

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