Natural fluorinated compounds

Fluorine, which does not occur freely in nature except for trace amounts in radioactive materials, is widely found in combination with other elements, accounting for ca 0.065 wt % of the earth s cmst (4). The most important natural source of fluorine for industrial purposes is the mineral fluorspar [14542-23-5] CaF2, which contains about 49% fluorine. Detailed annual reports regarding the worldwide production and reserves of this mineral are available (5). A more complete discussion of the various sources of fluorine-containing minerals is given elsewhere (see Fluorine compounds, inorganic). 

A compound containing two or three unsaturated groups would be expected to polymerize to a cross-linked, solid, and nonlinear thermosetting polymer. Fluorinated compounds that have only one unsaturated group can be used in a mixture with our monomers to polymerize to a solid polymer of a thermoset nature and this is a convenient way to enhance the ease of processing. 

The number of naturally occurring, organic fluorine compounds is very small indeed. Compound 1 is1 a nucleoside antibiotic that contains fluorine attached to the carbohydrate ring, replacing H-4 in the D-ribosyl moiety. The presence of fluorine was shown by -n.m.r.-, 19F-n.m.r.-, and mass-spectral data, and the structure of this compound has been confirmed by independent synthesis.9,10... 

The preparation of food for consumption, as well as manufacturing of various products from different raw materials, usually involves the application of several discrete unit operations and processes. Many operations, such as washing, trimming, milling, leaching, disintegrating, mechanical separation, and use of membrane techniques, may decrease the natural toxicity of some raw materials by eliminating specific undesirable components. Examples include the removal of most of the fluorine compounds from Antarctic krill... 

Trifluorothreonine is one of the rare fluorinated compounds found in nature (cf. Chapter 4). The best method for the synthesis of fluorothreonines is the acylation of an equivalent of glycinate anion by a fluoroacetic derivative. The four stereoisomers of monofluorothreonine have been prepared. A completely stereoselective chiral approach involves the alkylation of the Seebach imidazolidinone by fluoroacetyl chloride (Figure 5.16). ... 

This survey covers the most important information, published after 1960 in monographs, reviews, and papers of completely different nature in approach, experimental pathways and scientific weight and character. Therefore it is, as such, a cocktail of results, ranging from extensive, complete, statistically relevant toxic data of organo-fluorine compounds to the results of mere prescreening experiments. Some classes of compounds, considered to be nontoxic (see Section 5.1.) are, however, excluded. Bearing in mind the protection of scientists and their coworkers, this is the best approach, if conscious of adequate responsibility. This review is written for experimental chemists, rather than toxicologists. 

Fluorinated polymers are by nature inert and nontoxic materials. A certain toxicity may however be incorporated from additives added, e.g. perfluorooctanoic acid or traces of monomers. In addition, toxic organo-fluorine compounds may be generated from these polymers by high temperature decomposition.6-64- 16-118 Biological effects of fluorocarbon fibers have been described.119 Toxicities of polychlorotrifluoroethylenc oils (hydraulic fluids) have also been discussed.202... 

The formation of a solid, isolated by bubbling fluorine diluted with nitrogen into a solution of pyridine in trichlorofluoromethane at — 80 °C followed by filtering at low temperature, has been noted.30 The solid is considered to be a pyridine/fluorine compound with polar character however, spectral or other data on the structure of the pyridine/fluorine compound are presently not available, probably due to its explosive nature. This compound has been used for the fluorination of uracil and some chloroalkenes,30,31 but the adduct is of little use because of its violent decomposition above — 2CC. 

An important piece of evidence that some of this chlorine comes from the breakdown or CFCs was the unusually high levels of fluorine compounds detected in the Antarctic stratosphere. Whereas chlorine compounds come from a number of natural sources, fluorine compounds in nature are relatively rare. The source of this stratospheric fluorine, therefore, is most likely chlorofluoro-carbons. In addition to elevated fluorine levels, evidence of ozone depletion... 

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