Benzene fluorination

Figure 25 Left Side view of a portion of a stack in the structure of [137-benzene], Right Top view showing the sandwiched benzene molecule in [137-benzene], Fluorine and hydrogen atoms omitted for clarity. 

For the 11 substances, ammonia, 1,2-butanediol, 1,3-bntanediol, carbon monoxide, 1,1-diflnoroethane, ethane, heptane, hydrogen, hydrogen snlfide, methane, and propane, the liquid heat capacity CpL is calculated with Eq. (2) below. For all other compounds, Eq. (1) is nsed. For benzene, fluorine, and helinm, two sets of constants are given for Eq. (1) that cover different temperature ranges, as shown in the table. 

In the first route, in addition to carbon monoxide, benzene, fluorine and the anilide of phthalic acid are produced, while in the second besides carbon dioxide, benzene, biphenyl and fluorene are found [19]. 

Blesic, M., Canongia Lopes, J.N., Padua, A.A.H., Shimizu, K., Costa Gomes, M.F. and Rebelo, L.P.N., Phase equilibria in ionic liquid-aromatic compound mixtures, including Benzene Fluorination effects, J. Phys. Chem. B113, 7631-7636 (2009). 

The liquid crystals contained in LCDs comprises a number of diverse compounds, which are aromatic-based polymers with cyanogroup, benzene, fluorine (F), chlorine (Cl), and bromine (Br), etc [37]. These kinds of chemicals can do serious harm to ecosystem and human health without proper treatment while some can be recovered as... 

The most widely used reactions are those of electrophilic substitution, and under controlled conditions a maximum of three substituting groups, e.g. -NO2 (in the 1,3,5 positions) can be introduced by a nitric acid/sul-phuric acid mixture. Hot cone, sulphuric acid gives sulphonalion whilst halogens and a Lewis acid catalyst allow, e.g., chlorination or brom-ination. Other methods are required for introducing fluorine and iodine atoms. Benzene undergoes the Friedel-Crafts reaction. ... 

Chlorination is carried out m a manner similar to brommation and provides a ready route to chlorobenzene and related aryl chlorides Fluormation and lodmation of benzene and other arenes are rarely performed Fluorine is so reactive that its reaction with ben zene is difficult to control lodmation is very slow and has an unfavorable equilibrium constant Syntheses of aryl fluorides and aryl iodides are normally carried out by way of functional group transformations of arylammes these reactions will be described m Chapter 22... 

Turning now to electrophilic aromatic substitution in (trifluoromethyl)benzene we con sider the electronic properties of a trifluoromethyl group Because of their high elec tronegativity the three fluorine atoms polarize the electron distribution m their ct bonds to carbon so that carbon bears a partial positive charge... 

Chlorine Ammonia, acetylene, alcohols, alkanes, benzene, butadiene, carbon disulflde, dibutyl phthalate, ethers, fluorine, glycerol, hydrocarbons, hydrogen, sodium carbide, flnely divided metals, metal acetylides and carbides, nitrogen compounds, nonmetals, nonmetal hydrides, phosphorus compounds, polychlorobi-phenyl, silicones, steel, sulfldes, synthetic rubber, turpentine... 

Since, in fhe excifed sfafe, fhe fluorine atoms may be above or below fhe plane of fhe benzene ring fhe potential function for Vu is W-shaped, like fhaf in Figure 6.4f(b). Fitting the observed vibrational energy levels to the potential function in Equation (6.93) gives fhe heighf of fhe barrier to planarify as 78 cm. ... 

Manufacture. One commercial process features a three-stage saturation—rearomatization technique using benzene and fluorine gas as raw materials (73). Principal problems with this method are the complex nature of the process, its dependence on fluorine gas which is cosdy to produce, and the poor overall utilization of fluorine, because nearly one-half of the input fluorine is removed during the process. 

Bromine monofluoride [13863-59-7], BrF, can be prepared by the direct reaction of Br2 and F2, but because it readily disproportionates it has never been prepared in pure form (57). However, BrF can be prepared in situ by the reaction of Br2 with AgF in benzene (58) or by the reaction of A/-bromoacetamide and HF in ether (59). BrF adds to simple alkenes at room temperature to give products of trans-addition. Bromine trifluoride [7787-71-5], BrF, can be formed from gaseous fluorine and Hquid bromine (60). Bromine pentafluoride [7789-30-2], BrF, is formed from the reaction of BrF vapor with gaseous fluorine at 200°C (60). The tri- and pentafluorides are commercially available. As strong fluorinating agents they are useful in... 

Fig. 3. The percent volume swell in benzene after seven days at 21°C compared with the wt % of fluorine on standard recommended compounds. A, copolymers of vinyUdene fluoride—hexafluoropropylene B, terpolymers of vinyUdene fluoride—hexafluoropropylene—tetrafluoroethylene C, terpolymers of vinyhdene fluoride—hexafluoropropylene—tetrafluoroethylene-cure site monomer D, copolymer of tetrafluoroethylene—perfluoro(methyl vinyl ether)-cure...

Hexafluorobenzene [392-56-3] M 186.1, m 5.1°, b 79-80°, d 1.61, n 1.378. Main impurities are incompletely fluorinated benzenes. Purified by standing in contact with oleum for 4h at room temperature, repeating until the oleum does not become coloured. Washed several times with water, then dried with P2O5. Final purification was by repeated fractional crystn. 

Industrially, chlorine is obtained as a by-product in the electrolytic conversion of salt to sodium hydroxide. Hazardous reactions have occuned between chlorine and a variety of chemicals including acetylene, alcohols, aluminium, ammonia, benzene, carbon disulphide, diethyl ether, diethyl zinc, fluorine, hydrocarbons, hydrogen, ferric chloride, metal hydrides, non-metals such as boron and phosphorus, rubber, and steel. 

Partial fluorination [50] and perfluorination [5/] of aromatic systems can be accomplished electrochemically. A number of other reagents add fluorine to benzene and its derivatives, as elaborated in equation 5 [52, 53, 54, 551... 

Diselenides can also be oxidatively fluorinated, as shown in equation 18 [118, 119], Benzene selenyl fluoride is postulated as an intermediate during the fluo-roselenation of alkenes with diphenyl diselenide and xenon difluotide [73, 120]... 

Up to 20 products with different numbers of fluorine atoms and double bonds have been isolated from the fluonnation of benzene with silver difluoride [d], manganese trifluoride [7], potassium tetrafluoroargentate [d], and potassium hexafluoronickelate [24] The composition of the products depends on the fluorinating agents and on the temperature (Table 1)... 

Table 1. Comparison of Fluorination of Benzene with Manganese Trifluoride [7], Potassium Hexafluoronickelate [24], Silver Difluoride [6], and Potassium Tetrafluorocobaltate [6]...

Some derivatives of benzene can be fluorinated over cobalt trifluoride at lower temperatures. At 125 °C, 2H-tetrafluoronitrobenzene gives irans-2H,] -ni-trodecafluorocyclohexane, ci5-2ff, 1-nitrodecafluorocyclohexane, trans-5H,4-ni-... 

In quinoline and isoquinoline, the benzene ring is more receptive to fluorma-tion, its double bonds being saturated and the hydrogen atoms replaced in preference to those in the pyridine ring As with pyridine and its homologues, ring contraction takes place during fluorination with cesium tetrafluorocobaltate at... 

Results of the sulfur tetrafluoride fluorination of benzenecarboxylic acids strongly depend on the nature of a benzene ring substituent Benzoic, toluic, and particularly p-methoxybenzoic acids give poor yields of the respective benzotri-... 

A variety of media have been used for the Wallach fluorination reaction anhydrous hydrogen fluoride alone or with cosolvents such as methylene chloride, benzene, or tetrahydrofuran and hydrogen fluoride-pyridine alone or with co solvents such as benzene, glyme, or acetic acid [42,43, 46 50] Solutions of cesium fluoride, tetraethylammonium fluoride, or tetrabutylammonium fluoride in strong acids such as methanesulfonic acid or trifiuoroacetic acid with numerous cosolvents have also been studied [48, 49]... 

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