Polyfluorinated compounds

Markovskii, L.N., Furing, G.G., Shermolovich, Y.G., and Yakobson, G.G., Phosphorylation of polyfluorinated compounds. 3. Michaelis-Becker reaction in a series of polyfluoro-substituted benzene derivatives, Izv. Akad. Nauk S.S.S.R., 646, 1981. 

The exact mass of an ion (4 to 6 decimal points) reliably defines its elemental and isotopic composition, while the method is called high resolution mass spectrometry. The measurements are conducted manually or automatically (computerized). Manual measurements are based on the parallel acquisition of the peak of interest with the closest peak of an ion with the known composition. Any compound with an intense ion peak with m/z value in the region +10% may serve as a marker. The most widespread markers are perfluorokerosene, perfluorotributylamine, and other polyfluorinated compounds. The use of these compounds is based on their volatility, as well as on the fact that fluorine is a monoisotopic element. In the spectra of these compounds intense ion peaks randomly cover all the range between m/z 19 and M+. ... 

The unique physicochemical properties of polyfluorinated compounds (PFCs) render several challenges to analytical chemists endeavoring to measure PFCs at trace levels. 

The observation of large amounts of polyfluorinated compounds dissolved in the HF-phase was claimed not to be peculiar to these reactions but was said to be a normal part of all ECF reactions, and as such, said to contradict the zipper mechanism production of perfluorinated compounds, a pathway regarded as a support of the ECbECN process [62,172]. 

Dehydrohalogenations have been used for the preparation of many polyfluorinated compounds containing additional functionalities. Hydrogen fluoride is eliminated from 2//-tetrafluoro-propionyl fluoride (1) to give trifluoroacryloyl fluoride (2).87... 

Despite the fact that H+ (in terms of electrophilic reactions of polyfluorinated compounds only) is a relatively mild electrophile, strong protic acids (H0S02F, H0S02CF3, anhydrous HF) are widely used for generating electrophilic species. Thus, protonation of fluorine in HgF2 by anhydrous HF results in formation of the corresponding metal centered cation 3 [ 17,20] ... 

Fluorine-containing heterocyclic compounds play an important role in drug and pesticide design. The key methods of synthesis of these compounds are based on condensation and intramolecular cyclization processes induced by heteronucleophiles. They may affect the fluorine atoms of a benzene ring and the multiple bond of perfluoroolefins. Intramolecular cyclizations are characteristic of unsaturated polyfluorinated compounds. Therefore,... 

Houde, M., Wells, R. S., Fair, P. A., Bossart, G. D., Hohn, A. A., Rowles, T. K., et al. Polyfluorinated compounds in free-ranging bottlenose dolphins Tursiops truncatus) from the Gulf of Mexico and the Atlantic Ocean. Environ. Sci. TechnoL, 39 6591-6598 (2005). 

Other functional polyfluorinated compounds are available by addition of perhaloalkyl halides to enol derivatives, e.g. formation of 1 and 2 (see also Table 4). The adducts formed from enol acetates or enol ethers are not very stable and their hydrolysis to give a-perhaloalkyl aldehydes or ketones is often rapid. However, the enol derivatives can be transformed either to give ketals using alcohols or to give various products by oxidation and reduction reactions. The peculiar perfluoroalkyl iodide addition to enamines is spontaneous at room temperature, e.g. formation of 3. ... 

Another variation uses polyfluorinated compounds as the starting material for synthesis. In this technique, known as fluorous synthesis, the starting material is first derivatized with perflourinated groups [82], After the synthesis, a water-immiscible fluorocarbon solvent is added to the solution, effectively separating the product from the reaction mixture. The perfluorinated groups can then be removed to recover the purified product. 

The most economic route to polyfluorinated compounds is by exchange of chlorine with fluorine. A related reaction is the substitution of bromine by fluorine with chlorine monofluoride. The regio- and stereochemistry of this reaction has been investigated186 and preferential retention of configuration is observed. 

In many cases, di- and polyfluoropyridines can be prepared using the same reactions for preparation of monofluorinated analogues. The degree of fluorination in some cases can be controlled, however, often leading to mixmres of polyfluorinated compounds. Some polyfluoropyridines can be reduced back to di- or monofluor-opyridines, which can be successfully used for a selective synthesis of these compounds. 

The synthesis of F-labeled stilbenes [ F]2g, [ F]3g, and [ F]4e ( -isomers) by the FIorner-Wadsworth-Emmons reaction was accomplished [83]. This carbonyl-olefination reaction was performed via a multistep/one-pot reaction by the coupling of benzylic phosphonic acid esters (3,5-bis-methoxymethoxybenzyl)-phosphonic acid diethyl ester, (4-methoxymethoxybenzyl)phosphonic acid diethyl ester, and (4-dimethylaminobenzyl)phosphonic add diethyl ester with 4-[ F]fluor-obenzaldehyde. The radiochemical yields ranged from 9 to 22%. Three new polyfluorinated compounds ([( )-4-(4-bromostyryl)-2,3,5,6-tetrafluorobenzonitrile]x-[( )-4-(4-bromo-2,3,5,6-tetrafluorostyryl)benzonitrile]i K) were obtained by the Homer-Wadsworth-Emmons approach to study intermolecular interactions in the crystal state and the formation of cocrystals [84]. 

Recent alarms concern the potential toxicity of polyfluorinated compounds, in consideration of their ubiquitous presence in the environment, their persistence, and potential bioaccumulation and biomagniflcation properties. 

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). 

The main characteristics of polyfluorinated compounds are the replacement of most hydrogens by fluorine in the aliphatic chain structure. Some of these organic fluorine compounds are known as perfluorinated, which means that all hydrogens have been replaced with fluorine with a large variety of chemical forms and structures. Because of the diversity of fluoro organic substances, it is important to understand the developed chemical terminology. 

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]. 

Ahrens L, Felizeter S, Sturm R, Xie Z, Ebinghaus R (2009) Polyfluorinated compounds in waste water treatment plant effluents and surface waters along the River Elbe, Germany. Mar Pollut Bull 58(9) 1326-1333... 

Keywords Degradation Polyfluorinated compounds Sorption Water treatment... 

Abstract Per- and polyfluorinated compounds (PFC) are resistant to breakdown, are ubiquitous environmental contaminants which persist and may bioaccumulate through the food chain. In the recent years, increasing number of papers report high levels of PFC in blood, tissues, and breast milk from both occupationally and non-occupationally exposed human populations. The most important exposure pathways of PFC for humans are thought to be intake of drinking water, food and inhalation of dust. 

Keywords Dietary intake Food analysis Liquid chromatography Mass spectrometry Per- and polyfluorinated compounds Risk assessment... 

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