Fluorocarbons, saturated

The physical properties of saturated fluorocarbons and their analogous hydrocarbons differ in many respects [4 5] Sahirated fluorocarbons have the lowest dielectric constants, surface tensions, and refractive indexes of any liquids at room... 

These unusual properties of fluorocarbons reflect theu nonpolar character, low polarizability, and overall relatively weak intermolecular attractions Saturated perfluoro-terr-ammes and -dialkyl ethers also closely resemble fluorocarbons rather than typical amines or ethers in their physical properties [4,... 

Saturated fluorocarbons have the lowest surface tensions of any organic liquids and can completely wet almost any surface. Perfluonnated amines and ethers also... 

Almost all of the biomedical research done in the 25 years following the liquid-breathing work was conducted with commercially available fluorocarbons manufactured for various industnal uses by the electrochemical Simons process (fluonnation in a hydrofluoric acid solution) or the cobalt fluoride process (fluori-nation with this solid in a furnace at about 200 C) These processes tended to yield many by-products, partly because they were, to some extent, free radical reactions and partly because it was difficult to easily achieve complete fluonnation Aromatic hydrocarbons gave better products with the cobalt tnfluonde [73] method, whereas saturated hydrocarbons yielded better products with fluonnation using diluted or cooled gaseous fluorine (Lagow) Incompletely fluormated matenal was either... 

Institute of Science end Technology This biennial review covers 1969 arxl 1970 literature on saturated fluorocarbons, fluorocarbon halides ar>d hydrides, arnf poly-flOro-organic compounds and their spectroscopic properties 307pp 7 00... 

The lower members, e.g. CF4 and C2F6, are colourless, odourless gases of very low toxicity. By comparison with the fluoro-acetates they may be said in general to be non-toxic. This is understandable, particularly with regard to the simple saturated fluorocarbons, as they do not contain the FCH2CO group and are not likely to give rise to it in the animal body. Recently,... 

A liquid perfluorocarbon was being used as solvent in an oxidation by oxygen under pressure more energy was released than expected [1], It is cautioned that fluorocarbons are not inert to oxidation, presumably to carbonyl fluoride. An explosion has been experienced with perfluorotoluene in like circumstances [2], A correspondent reports that perfluorotoluene is flammable in air, more saturated perfluorocarbons in pure oxygen [3], Another detailed the combustion performance of polytetrafluoroethylene 148 kcal/mole ignition temperature not below 465°C at 7000 psi of oxygen [4], the product is mostly carbonyl fluoride. Other oxidants may also present a risk in extreme circumstances. 

Interestingly, we have found that microbubble deflation in the ultrasound field is unusually slow for the microbubbles that contain perfluorocarbon gas when the surrounding medium is depleted of air and saturated with the same fluorocarbon gas [57]. So, perhaps in an air-saturated environment the ultra-sound-mediated destruction of microbubbles may depend on the influx of air into the bubbles, not just on the perfluorocarbon loss. 

In tests of materials saturated with liq oxygen and subjected to 71-75 lb drop weight tests, the following were found acceptable (one de-tonation/40 impacts or none/20) fluorocarbon oils greases, graphite, halogenated biphenyl molybdenum disulfide lubricants, polyethylene... 

In the Liquid-Phase Photofluorination [39,44] process the reactant is injected at a very slow constant rate into an inert fluorocarbon solvent which is saturated by fluorine and under U.V. irradiation. Conditions are chosen to ensure that the concentration of fluorine and fluorine radicals is always much higher than the concentration of the substrate. This method is only suitable for the perfluorination of substrates, such as partially fluorinated ethers (see Section 2.5) and amines (see Section 2.7), that are both soluble in perfluorocarbon solvents and can withstand such vigorous reaction conditions. 

This reaction is easily controlled, uses an inexpensive reagent, and gives benign products that are easily disposable. The method also shows promise as a means of converting inert saturated fluorocarbons into more reactive fiuoroalkenes or fluoroarenes for use in syntheses. 

J. Burdeniuc and R. H. Crabtree, Mineralization of chlorofluorocarbons and aromatization of saturated fluorocarbons by a convenient thermal process. Science, 271, 340-341 (1996). 

Compounds with a high LUMO and a low HOMO (Figure 5.5a) will be chemically inert. Saturated hydrocarbons, fluorocarbons, and to some extent ethers fall in this category. 

The products of the electrochemical perfluorination of aromatic and heteroaromatic compounds are the corresponding perfluorinated cyclic and heterocyclic alkanes.28 and also per-fluorinated derivatives of the heteroaromatic compounds. Perfluorocyclohexane is the principal product from the electrochemical fluorination of benzene and fluorobenzene. Chloro derivatives of perfluorocyclohexane are produced from chlorobenzenes. Anisoles give fully saturated per-fluoro ethers, together with cleavage products. Extensive cleavage is observed in the fluorination of benzenethiols. Chloropyridines, fluorocarbons and sulfur hexafluoride or nitrogen trifluoride are characteristic byproducts from the above scries of reactions. 

Phase-separated monolayers and liposomes were characterized by R. Elbert1011 who synthesized saturated and polymerizable fluorocarbon amphiphiles (59, 60, 61) and investigated their mixing behavior with CH2-analogues and natural lipids. In these systems the fluorocarbon compounds are incompatible with hydrocarbon lipids in a wide range of compositions and tend to form domains of pure fluorocarbon and hydrocarbon amphiphiles. The domains can be visualized by freeze-fracture electron microscopy. 

Fluorocarbon derivatives have another interesting and potentially useful property. They dissolve large quantities of oxygen. This fact, combined with their nontoxicity, has led to their use as blood replacements in heart surgery on experimental animals. Mice can live totally immersed in oxygen-saturated liquid fluorocarbons. 

Interestingly, some of these processes are mimicked by reactions with nucleophiles and it is clear that one-electron transfer from the nucleophile is involved. Indeed, a remarkable process [32], Scheme 10,begins with perfluorodecalin (26) and must proceed via intermediate polyfluorocycloalkene derivatives, e.g. (27), in which successive electron transfers occur, and the final product is a naphthalene derivative (28). So far, this is the only case in which a saturated per-fluorocarbon has been reported to react in this way, to give meaningful products. 

The pentamer of tetrafluoroethene (66) (Scheme 29) is an unusual example of type (96) and reacts readily with nucleophiles [129] (Scheme 65). In contrast, (66) undergoes a remarkable reaction with aqueous triethylamine, producing the dihydrofuran derivative (101) and the process formally involves a direct intramolecular displacement of fluorine from a saturated site and a mechanism has been advanced (Scheme 66) which accounts for the product formed [126]. Understandably, this process is not easily accepted [3, 130] because it has essentially no precedent. Indeed, it is well established that nucleophilic displacement from saturated sites in fluorocarbons occurs only in exceptional circumstances. Consequently, other mechanisms have been advanced, which seem no more convincing [3, 130]. It should be remembered that the major point in favour of the step (100) to (101) (Scheme 66) is that the nucleophile is generated in close proximity to the reaction centre because of the special geometry of this situation. Consequently, much of the otherwise high energy/entropy barrier has already been overcome in this case. 

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