Fluorocarbons, reaction with

Reactions with Organic Compounds. Tetrafluoroethylene and OF2 react spontaneously to form C2F and COF2. Ethylene and OF2 may react explosively, but under controlled conditions monofluoroethane and 1,2-difluoroethane can be recovered (33). Benzene is oxidized to quinone and hydroquinone by OF2. Methanol and ethanol are oxidized at room temperature (4). Organic amines are extensively degraded by OF2 at room temperature, but primary aHphatic amines in a fluorocarbon solvent at —42°C are smoothly oxidized to the corresponding nitroso compounds (34). 

Reaction with a Metal Fluoride. A second technique for hydrogen substitution is the reaction of a higher valence metal fluoride with a hydrocarbon to form a fluorocarbon ... 

Chloroform is mainly used to produce chlorodifluoromethane (Fluorocarbon 22) by the reaction with hydrogen fluoride ... 

Terpolymers in which the acrylate monomer is the major component are useful as ethylene-acrylate elastomers (trade name Vamac) [Hagman and Crary, 1985]. A small amount of an alkenoic acid is present to introduce sites (C=C) for subsequent crosslinking via reaction with primary diamines (Sec. 9-2d). These elastomers have excellent oil resistance and stability over a wide temperature range (—50 to 200°C). They are superior to nitrile and chloroprene rubbers. Although not superior to silicone and fluorocarbon elastomers, they are less costly uses include automotive (hydraulic system seals, hoses) and wire and cable insulation. 

Thus, Tokuyama Soda KK have patented [149] a piece of technology for the combustion of the hydrogen gas with the fluorocarbons produced in the ECF reaction with the objective of recovering HF which would otherwise be lost. 

Fullerenes can be derivatized by various means. For example, reaction with fluorine gas proceeds stepwise to the formation of colorless CeoFeo, which, according to the 19F nuclear magnetic resonance (NMR) spectrum, contains just one type of F site and so evidently retains a high degree of symmetry.9 In view of the low adhesion typical of fluorocarbons, this spherical molecule is expected to have extraordinary lubricant properties. Curiously, bromination of Ceo is reversible on heating otherwise, the reactions of fullerenes resemble those of alkenes or arenes (aromatic hydrocarbons). 

Uranium Hexafluoride (Uranyl hexafluoride). UF6 mw 352.02 colorless, deliq monocl crysts mp 64.5—64.8° bp, subl at 56.2° d 4.68g/cc at 21°. Sol in liq Br, Cl2, C tetrachloride, sym-tetrachlorethane and fluorocarbons. Reacts with extreme violence with benz, ethanol, toluene, w or xylene. Prepn is by reaction of dried, powdered U308 with F gas above 600°. Product purification is by vac sublimation in a quartz appar. The vapor behaves as a nearly perfect gas. The compd has a AHf of 2197.7 1,8KJ/mole. It is used in the gaseous diffusion process for the sepn of U isotopes Refs 1) Gmelin, Syst Nr 55 (1940), 124-31 2) G. Brauer, Handbook of Preparative Inorganic Chemistry , Academic Press, NY (1963), 262 3) CondChemDict (1977), 904-05... 

The fact that functionalization of polymers and small molecules is observed to occur predominately on terminal (methyl) carbon atoms does not imply that the oxyfluorination reaction is truly selective. Although the reaction mechanism has not been studied in detail, it is undoubtedly a free-radical process. Molecular oxygen reacts spontaneously with the fluorocarbon—hydrogen radicals generated by fluorine during the fluorination process. Acid fluorides are retained on terminal carbon atoms because they are stable in 1 atm of elemental fluorine. Hypofluorites, which may be short-lived intermediates of oxygen reactions with methylene radical sites along the carbon chain, are not observed in the functionalized polymers. It is probable that, if they are intermediates, they are cleaved and removed by the excess elemental fluorine. 

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. 

Cn>8 aldehydes and heavy side reactions with water Persistence of fluorocarbons... 

Only perfluorocyclopentene has been synthesised directly by this route it can be seen that, here, allylic rearrangements can occur to make all positions potentially vinylic and therefore reactive [64]. An analogous situation applies to hexachlorobutadiene. These reactions may also be carried out with potassium fluoride that has been exposed to Sulpholan or 18-crown-6, but then suspended in a fluorocarbon. Under these conditions, a significant proportion of hexafluoro-2-butyne is formed, presumably because the latter is extracted into the fluorocarbon, pre-empting further reaction with fluoride [65] (Figure 2.14). 

Part of the interest in fluorocarbon systems lies in a comparison of the chemistry, and particularly reaction mechanisms, of fluorocarbon derivatives with those of the corresponding hydrocarbon compounds. Indeed, such comparisons pose quite a strenuous test on our theories of organic chemistry. As will be seen, our understanding of the influence of carbon-fluorine bonds on reaction mechanisms has made considerable progress. Nevertheless, it must be emphasised that fluorocarbon derivatives present much more complicated systems than their corresponding hydrocarbon compounds because, in addition to effects arising from different electronegativities, the effect of the lone pairs of electrons of fluorine that are not involved in o-bonds must be taken into consideration. Furthermore, the relative importance of these effects seems to be very dependent on the centre to which the fluorine is attached. 

Either fusion with alkali metals or reaction with aUcali-metal complexes with aromatic hydrocarbons will break down most fluorocarbon systems, due to the high electron affinities of these systems. Such reactions form the basis of some methods of elemental analysis [13], the fluorine being estimated as hydrogen fluoride after ion exchange. Surface defluorination of PTFE occurs with alkali metals and using other techniques [14]. Per-fluorocycloalkanes give aromatic compounds by passage over hot iron and this provides a potential route to a variety of perfluoroaromatic systems (Chapter 9, Section IB). 

Some of the common anthropogenic chlorinated molecules such as CH3CCL (Methylchloroform) and CHCIF2 (Fluorocarbon-22) are not fully halogenated, and contain C-H bonds which are susceptible to reaction with tropospheric HO radicals. The most abundant of these in its present atmospheric concentration is CHjCCh which is decomposed by reaction (5). 

Fluorine contamination has been reported in various environments and applications in the past. It has shown up in plasma processing [10-18], as crosscontamination from storage in contaminated containers or with contaminated samples [14,18], and modification of aluminum deposited on fluoropolymer substrates and other polymers having fluorine-based plasma treatments has also been observed [19-21]. Fluorocarbon lubricants have also been noted to modify the oxide structures on aluminum alloys [22,23], and the degradation of AI2O3 catalytic supports has been associated with fluoride conversion during reactions with fluorocarbons [24]. Alloy oxide modification has also been well noted in the presence of fluorine compounds not of the fluorocarbon family [25]. 

The theoretical study of incendiary reactions has been aided by the use of com.puter programs for the study of the equil products (Refs 15 41), as well as for the prediction of the adiabatic reaction temps. An example of the complexity of the reaction products of a fluorocarbon, compounded with 5% epoxy binder, is given by Tanner (Ref 80). It will be observed, that only the carbon remains as solid product, and that the effect of the fluorine is one of increasing the fraction of gaseous products, as well as to provide the thermal energy (see Table 8)... 

Carbanions, generated by reaction of fluoride ion with unsaturated fluorocarbons, may be trapped by reaction with activated polyfluoroaromatic compounds, resulting in the introduction of polyfluoroalkyl groups.303 307 These are, of course, reminiscent of familiar cationic processes and may be thought of as nucleophilic Friedel-Crafts reactions (Eqs. 80 and 81).307... 

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