Fluorinated organic substances compounds

This chapter deals with recent advances in the application of electrochemical electron transfer reactions to the synthesis of fluorinated organic substances. The effect of fluorine atoms on the reduction and oxidation potentials of organic compounds is discussed first. Subsequently, recent applications of the electrochemistry to the conversion and functionalization of fluoro-organics (building-block approach) are described. Finally, methods for selective electrochemical fluorination of organic molecules (direct fluorination approach) are briefly considered. 

Fluorinated organic substances are classified into two groups, perfluoro compounds and partially fluorinated compounds. Substances in the former class are widely utilized as functional materials while those in the latter family find biological uses as pharmaceuticals and agrochemicals. 

LC-MS/MS is recognized as the technique of choice for analysing many environmental pollutants, for example fluorinated alkyl substances (FASs). These organic compounds contain carbon and fluorine, and arise as a result of biological and geochemical processes, and may be produced synthetically for heat-, oil- and water-resistant products. FAS contaminants have been identihed in environmental and biological samples, and can bioaccumulate to toxic levels. LC-MS/MS has been widely used to study FAS contaminants in water, sediment and biological samples, and may confirm and extend more limited LC-MS studies. 

The preparation of organic fluorine compounds also requires methods different from those used for the other organic halogen compoimds. Because of the high heat of formation of CF (231 kcal.) and HF (64 kcal.), the treatment of organic substances with fluorine results mainly in the formation of CF and HF, in addition to charred and tarry substances, while no appreciable quantities of normal substitution products are obtained. This method, which is used in Industry for the production of perfluorocarbons, is not suitable for work on a laboratory scale. Organic fluorine compounds are prepared in reasonable yields chiefly by the following procedures. 

The interhalogen compounds are highly reactive substances, especially those containing fluorine. Chlorine trifluoride (CIFj) of b.p. 11°C is in many respects more reactive than fluorine and flames instantaneously not only with many organic substances but even with aluminum oxide and magnesium oxide. Similar in behavior is bromine trifluoride (BrF ) of m.p. 8.8 C and b.p. IBSX. Other interhalogen compounds, all very reactive, are CIF, BrF, BrF, IFj, and IF,. More recently discovered was the compound chlorine pentafluoride (ClF ) of m.p, approximately — 103"C and a b.p. of — 18.1 C. 

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. 

These are liquids which dissolve other substances. They can be more or less pme organic chemical compounds or mixtures. They can be synthetic or if not natural, obtained from natural somees for example, mar r of the oil refinery cuts sold as industrial solvents are mixtures of organic chemical compoimds which are distilled from petroleum or distilled from it after cracking (chemical conversion). Matty are flammable, but synthetic compoimds where atoms of chlorine or fluorine are built-in (so-called safety solvents) may be non-flammable. The substance 1,1,1 - trichloroethane used in fabric protector sprays and fat-dissolving drain cleaners, is not flammable. However, beware of the words safety solvent . The solvents with chlorine in them, and to a lesser extent fluorine, still pose toxicity hazards, or a hazard to the ozone layer. Some classes of organic solvents are shown in Table 9.1. 

Fluorine is the most powerful oxidizing agent known, reacting with practically all organic and inorganic substances. Exceptions are metal fluorides and a few completely fluorinated organic compounds in pure form. However, the latter may also react with fluorine if they are contaminated with a combustible material or in high flow situations. 

In many cases, industrial wastes contain valuable products such as high-value metals, acids, and other substances which can be used for manufacturing by-products, and these, when recovered, will yield high economic returns. Also obtainable are solvents, recovered with activated-carbon adsorption used for removal and recycling of solvents contained in the waste as vapors these solvents include hydrocarbons, esters, alcohols, freons, ketones, and chlorinated or fluorinated organic compounds. 

---