Fluorinated aromatic hydrocarbons

FIGURE 9.27 Transformation of fluorinated substrates by toluene 2,3-dioxygenase and yields (%). (From Neilson, A.H. and Allard, A.-S., The Handbook of Environmental Chemistry, Vol. 3R, Springer Verlag, 2002, pp. 1-74. With permission.) 

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Flecainide (Tambocor) is a fluorinated aromatic hydrocarbon examined initially for its local anesthetic action and subsequently found to have antiarrhythmic effects. Flecainide inhibits the sodium channel, leading to conduction slowing in all parts of the heart, but most notably in the His-Purkinje system and ventricular myocardium. It has relatively minor effects on repolarization. Flecainide also inhibits abnormal auto-maticity. 

Among the fluorinating agents of practical significance,44 only fluoroxytrifluoro-methane45 and iV-fluoroperfluoroalkylsulfonimides46 were shown to fluorinate aromatic hydrocarbons by an electrophilic mechanism. 

Samojlowicz C, Bieniek M, Zarecki A, Kadyrov R, Grela K. The doping effect of fluorinated aromatic hydrocarbon solvents on the performance of common olefin metathesis catalysts application in the preparation of biologically active compounds. Chem Commun. 2008 (47) 6282-6284. 

Scheme 66 C-H bond activation of fluorinated aromatic hydrocarbons by [Rh(Tp )(K -CN CH2CMe3)(K -CNCH2CIVle3)].

Evans ME, Burke CL, Yaibuathes S, Clot E, Eisenstein O, Jones WD. Energetics of C-H bond activation of fluorinated aromatic, hydrocarbons using a [Tp Rh (CNneopentyl)] complex. J Am Chem Soc. 2009 131 13464-13473. 

Steric Factors. Initially, most of the coUisions of fluorine molecules with saturated or aromatic hydrocarbons occur at a hydrogen site or at a TT-bond (unsaturated) site. When coUision occurs at the TT-bond, the double bond disappears but the single bond remains because the energy released in initiation (eq. 4) is insufficient to fracture the carbon—carbon single bond. Once carbon—fluorine bonds have begun to form on the carbon skeleton of either an unsaturated or alkane system, the carbon skeleton is somewhat stericaUy protected by the sheath of fluorine atoms. Figure 2, which shows the crowded hehcal arrangement of fluorine around the carbon backbone of polytetrafluoroethylene (PTFE), is an example of an extreme case of steric protection of carbon—carbon bonds (29). 

Oxidative Fluorination of Aromatic Hydrocarbons. The economically attractive oxidative fluorination of side chains in aromatic hydrocarbons with lead dioxide or nickel dioxide in Hquid HF stops at the ben2al fluoride stage (67% yield) (124). 

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... 

In fact, fluorinated polyphosphazenes are usually considered to be extremely stable towards chemical agents and aggressives due to the presence of C-F bonds in the side phosphorus substituents. PTFEP, for instance, appears to be completely insensitive to several, most common, solvents (aliphatic and aromatic hydrocarbons, alcohols and water), to acids (e.g. acetic acid), and to bases (e.g. pyridine and concentrated NaOH solutions), although some decomposition could be observed in triethylamine and in concentrated H2SO4 [41]. Phos-phazene fluoroelastomers, moreover, are known to be completely insoluble in aromatic solvents [533] and petroleum-resistant materials [502-506,552]. 

The introduction of the halogens onto aromatic rings by electrophilic substitution is an important synthetic procedure. Chlorine and bromine are reactive toward aromatic hydrocarbons, but Lewis acid catalysts are normally needed to achieve desirable rates. Elemental fluorine reacts very exothermically and careful control of conditions is required. Molecular iodine can effect substitution only on very reactive aromatics, but a number of more reactive iodination reagents have been developed. 

Effects of Methyl and Fluorine Substitution on the Metabolic Activation and Tumorigenicity of Polycyclic Aromatic Hydrocarbons... 

In contrast to saturated hydrocarbons, the unsaturated hydrocarbons react with atomic fluorine by two pathways, i.e. (atomic fluorine addition at >C=C< double bond and hydrogen substitution by fluorine atoms. The reaction of fluorine with aromatic hydrocarbons proceeds with the formation of F-derivatives and hydrogen atoms break off ... 

Aromatic hydrazines, 13 573 Aromatic hydrocarbons, 18 593 biodegradability of, 25 826 composition of, 25 168 as diluents, 10 430 fluorinated, 11 866 nitration of, 17 161 separation of, 10 782-785 as solvents for poly(ethylene oxide),... 

The incorporation of polar groups in unvulcanized polymers reduces their solubility in benzene. Thus the copolymer of acrylonitrile and butadiene (NBR), polychlorobutadiene (Neoprene), and fluorinated EP (the copolymer of ethylene and propylene) are less soluble in benzene and lubricating oils than the previously cited elastomers. Likewise, silicones and phosphazene elastomers, as well as elastomeric polyfluorocarbons, are insoluble in many oils and aromatic hydrocarbons because of their extremely low solubility parameters (silicons 7-8 H polytetrafluoroethylene 6.2 benzene 9.2 toluene 8.9 pine oil P.6). 

Mesophase pitch, consisting of a mixture of various aromatic hydrocarbons, reacts with fluorine between 50-130°C to give pitch fluorides [56] with the composition CFj 3 to CF159. These materials have a higher fluorine content than graphite fluoride (see Section 2.7), have very low surface energy and are soluble in some fluorinated solvents. 

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). 

Instead of methylaluminoxane, fluorinated aromatic compounds, such as a, a, n-trifluorotoluene can be used (36). The polymerization yield may be deteriorated when the mole ratio is out of the range, i.e., the fluorine-containing aromatic hydrocarbon compound is used in an amount of less than one mole with respect to one mole of the nickel salt compound. Otherwise, when the fluorine-containing aromatic hydrocarbon compound is used in an amount of more than 100 moles with respect to one mole of the nickel salt compound, there occurs a discoloration of the product with a deterioration of efficiency in the aspect of economy. 

Y.C. Jang and H.K. Sung, Method for preparing a homo-and co-poly-mers by polymerization of cyclic olefin compounds using fluorine-containing aromatic hydrocarbon compound as catalyst activator, US Patent 6998450, assigned to Korea Kumho Petrochemical Co., Ltd. (Seoul, KR), February 14,2006. 

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