Perfluorinated hydrocarbon

Another approach to the fabrication of LB films from prefonned polymers is to fonn a hydrophobic main chain by reacting monomers tenninated by a vinyl group [102, 103, 104, 105 and 106]. The side groups studied also included perfluorinated hydrocarbon chains, which tilt with respect to the nonnal to the plane of the film, whereas the analogous ordinary hydrocarbon chains do not [105]. 

Daikin Industries Osaka, Japan (CF ), IF, perfluorinated hydrocarbons moderate... 

Solvay Fluor und Derivate, GmbH Haimover, Germany SFg, IF, perfluorinated hydrocarbons, CF p large... 

Perfluorinated hydrocarbons are much weaker eluents ilthan aliphatic hydrocarbons and they can have negative e" values. They are"useful for separating nonpolar sample components such as aliphatic >ydrocarbons, olefins, and benzene. However, their limited solubility fof the higher alkanes (> C,() and their high cost limits their use as eluents, particulariy because the separation of such samples can also be porjbrmed by gas chromatography. ... 

As mentioned in Section 6.3, band waggoning in the early 1990s resulted in several proposals for uses of fullerene [30a] which until now have not reached fruition. High-temperature fullerene superconductors and a C60F60 lubricant illustrate the point. The latter, ball shaped perfluorinated hydrocarbon, should have revolutionized industry by minimizing friction losses of energy. The compound was synthesized. However, it proved unstable. Moreover, it... 

We have introduced fluorine (as CF3) only at the end of the added side chains. Furthermore, less than 10% of the residues have been so modified. Hence I think the perturbation due to F should be minor. But it is perfectly true that perfluorinated hydrocarbons, with all CH s replaced by CF s, are incompatible with ordinary hydrocarbons. We have been aware of this incompatibility, and hence have kept the fraction of CF bonds in our polymer very low. 

Reactions in fluorous solvents (usually perfluorinated hydrocarbons) have been described [65], and benzotrifluoride (PhCF3) has shown to be a useful replacement for CH2C12 [66], These solvents are significantly more expensive than solvents routinely used today, but prices may drop as applications and demand rise. 

The continuous-wave COj laser-induced decomposition of hexafluoropropanone, sensitized with SF, gave COF 3, perfluorinated hydrocarbons, carbon monoxide, and trifluoroethanoyl fluoride [1641] ... 

Carbynoid systems obtained from perfluorinated hydrocarbons have shown to decay faster when heated although a systematic characterization of the effect of thermal annealing has not been provided [9]. We observe that moderate thermal heating in UHV conditions strongly affects the decay behavior of the sp chains in nanostructured carbon. The sp phase seems to be... 

Kavan, L. Hlavaty, J. Carbon nanostructures from perfluorinated hydrocarbons. Carbon 1999, 37, 1863-1865. 

Although perfluorinated hydrocarbons are well known, they have only recently found application in organic chemistry as a useful class of solvents. Their physical properties mice them unique for their use as reaction media. Since perfluorocarbons are immiscible with many common organic solvents, they are suitable for the formation of biphasic systems. This overview describes the utilization of perfluorocarbons as reaction media for various kinds of reaction such as oxidation, bromination, etc. In addition, a novel biphase reaction system based on perfluorinated solvents as well as its application in organic synthesis is presented. 

The achievements in asymmetric biphasic catalysis are not very encouraging except for some hydrogenation reactions. Nevertheless, the simplicity of catalyst-product separation in biphasic systems should be a challenge to improve activity and stereoselectivity. New developments of biphasic systems containing a hydrocarbon and a perfluorinated hydrocarbon which are miscible at slighly enhanced temperature and separable at ambient temperature have not yet been used in asymmetric catalysis [24,25]. 

The chemical dehalogenation of perfluorinated hydrocarbons Uke perfluorocy-clopentene, perfluoronaphthalene, or perfluorodecahn leads to carbon materials, too. At first, unstable carbyne phases are generated, which may be transformed then into nanotubes. The same is true for the decomposition of 1,3,5-hexatriyne that forms nanotubes as well. The yields, however, are rather low, with only 1-2% of the resulting material actually being MWNT. In addition, fullerenes and onionlike carbon particles are obtained. 

Under suitable conditions, the reaction of perfluorinated hydrocarbons like teflon (PTFE) or perfluoronaphthalene with alkali amalgam yields carbon nanostructures as weU. The reductive dehalogenation generates intermediate polyynes that subsequently condense to give the respective graphene structures. Normally, a rruxture of carbon nanotubes and onions is obtained. 

In the previous section it was suggested that the parent polymer structure considerably influence the physical properties of the derived polysulfonates, imparting to them some of the mechanical and thermal properties of the precursors. This trend is particularly evident in the case of the perfluorinated hydrocarbon polymers. Polymers of this kind, such as e.g., poly(tetrafluoroethylene) (PTFE) are exceptional in their inertness to offensive environment, solvent resistance and high-temperature stability. These considerations led in the sixties to the development of unique sulfonic-acid derivatives of fluorocarbon copolymers by the DuPont Company. While several compositions were disclosed in the patent literature51, the preferred composition, which is the basis for the commercial Nafion ion-exchange membrane, is a copolymer of tetrafluoroethylene with a perfluorinated vinyl ether/sulfonyl fluoride52 ... 

Caution Higher temperature (500-700°C for graphite, 400-450°C for charcoal) can cause severe expiosions and formation of CF4, CjFg and other perfluorinated hydrocarbons. Thus fiuorination of graphite should be regarded as a potentially hazardous experiment. 

Additional methods to eliminate temperature gradients include the use of coaxial inserts to hold the solution within a conventional NMR tube so as to jacket the sample, with the intermediate space filled with a perfluorinated hydrocarbon oil [19], an NMR silent solvent [20] or simply just empty space [21], the last of these having been demonstrated specifically for low-temperature ( 230 K) studies. 

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