Fluorobenzene Fluoro derivatives

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. 

Several compounds, including many deuterated and fluoro derivatives, have been used in the published literature. These include fluorobenzene, pentafluo-robenzene, l,2-dichlorobenzene-d4, l-chloro-2-fluorobenzene, 1,4-difluoroben-zene, l,2-dichloroethane-d4, 1,4-dichlorobutane, and 2-bromo-l-chloropropane. U.S. EPA has set the tuning criteria for bromofluorobenzene and decafluorotriph-enylphosphine as tuning compounds for volatile and semivolatile organic compounds. (See Chapter 1.4)... 

Trifluoromethyl hypofluorite reacts with a variety of aromatic systems, with the ease and extent of substitution dependent on the nature of the substituent already present. At low conversion (41%). benzene is converted into a mixture of fluorobenzene (93%) and (tri-fluoromethoxy)benzene(5%) when the conversion is increased, multifluorinated products become significant impurities. The fluorinations of aromatics containing alky] substituents, e.g. toluene, with trifluoromethyl hypofluorite yield complex mixtures of products with poor material balance. TV-Substituted aniline derivatives 11 react with trifluoromethyl hypofluorite to give high yields of ortho- and / ara-monosubstituted fluoro derivatives. 

We are focusing on the five lowest electronic states of the benzene cation and its fluoro derivatives, namely the mono-, di- (three different isomers) and tri- (1,2,3-isomer) fluorobenzene cations. These states lie, for all six cations, in the energy range from 9 to 13-14 eV above the electronic ground state of the respective neutral species. They give rise to the low energy band systems of the experimental photoelectron spectra [70]. 

Another report demonstrates the capability of providing quantitative information on the extent of conversion of a solid-phase material. This method may be applicable to a wide range of reaction chemistries and resin-supported materials. These authors use NMR to quantify the extent of the derivatization of functionalized polymeric material with a fluorinated substrate. Thus the rate of the reaetion of Merrifield resin with 2-lluo-rophenol was examined. At various time intervals portions of the reacting resins were removed and were exhaustively reacted with excess 4-lluo-rophenol. Analysis of the resin samples shows two signals (Scheme 2.9), one for the 2-fluoro derivative at -134 ppm and the other for the 4-fluoro derivative at -124ppm. Quantitative information on the extent of the reaction was obtained by measuring the relative intensities of the resin bound fluorine and a known concentration of an internal standard in solution, such as fluorobenzene. It was noted that there needed to be a sufficient time delay between the RF pulses so that the solid-phase and solution-phase nuclei would be similarly relaxed in the F NMR spectra. This method provided excellent correlation for resin-bound F atom content in samples containing 30 mg resin samples blended to various extents with 100% 2-fluorophenyl Merrifield ether and unfunctionalized Merrifield resin. This fluorophenol based assay was then used to optimize the attaehment of an epoxide to the Merrifield resin (Scheme 2.10). The alkylation reaetion was monitored at... 

Desilylation-electrophilic substitution of trimethylsilylbenzenes provides a route to a number of mefa-substituted fluorobenzene derivatives such as 3-fluoro-acetophenone, which is unobtainable under normal Friedel-Crafts conditions [36] (equation 25). 

Decomposition of the diazonium trifluorotris(perfluoroalkyl)phosphates proceeds mildly, without formation of tars (since no strong Lewis acid evolves), and with high yields of the substituted fluorobenzenes. For example, l-fluoro-4-nitrobenzene is obtained in a far better yield (82%) than from 4-nitrobenzenediazonium hexafluorophosphate or tetrafluoroborate [cf. formation of 2 (R = 4-N02)]. The coproduced difluorotris(perfluoroalkyl)-A5-phosphanes are not soluble in the resulting fluorobenzene derivatives and, because of their high density, form a lower layer which is readily separated. Thus, these difluoro-25-phosphanes can be regenerated quantitatively and used repeatedly. 

Studies by Kiersznicki and co-workers demonstrated that chlorosulfonic acid is an effective catalyst in the alkylation of arenes by reaction with alkenes. Benzene, toluene and ethylbenzene were alkylated by propene, elhene and 2-butene in the presence of chlorosulfonic acid which strongly catalysed the alkylations and inhibited polyalkylation. Increasing the concentration of the catalyst enhanced the proportion of /7-isomers in the products. Fluoro-, chloro-and bromobenzenes were similarly alkylated by reaction with C2-C4 alkenes using chlorosulfonic acid as catalyst. The optimum alkylation conditions were with a halobenzene alkene ratio of 1 0.25, a catalyst concentration of 0.33 mol mol" of fluorobenzene and 0.5 mol mol of the other halobenzenes, a temperature of 70 C and a reaction time of 2 hours. Alkylation with propene gave haloisopropylbenzenes the monoalkyl products were obtained as o-, m- and p- mixtures, the relative amounts depended on the quantity of catalyst used and the by-products were dialkyl derivatives, sulfonic acids and sulfones. In the reaction of benzene with propene, fluorosulfonic acid was a more potent alkylation catalyst than chlorosulfonic acid. ... 

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