- The Preparation and Characterization of Radical Cation Salts Derived from Perfluorobenzene, Perfluorotoluene, and Perfluoronaphthalene
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The salts C6F6+AsF6- (yellow), C6F5CF3- (lime green), and C10F8+AsF6- (dark green) may be prepared by electron oxidation of the appropriate perfluoro aromatic molecule with O2+AsF6-.Other O2+ salts can be similarly employed as can the more strongly oxidizing transition-metal hexafluorides, but salts of the latter are more labile than their AsF- relatives.C6F6+AsF6- is a convenient electron oxidizer (C6F6AsF6+C10F8 -> C10F8AsF6+C6F6) since that which remains from the reaction decomposes at room temperature to volatile products (2C6F6AsF6 -> C6F6+1,4-C6F8+2AsF5).Magnetic susceptibilities for C6F6AsF6 and C10F8AsF6 approximate to Curie law behavior, and g values are close to free-electron values.X-ray diffraction data (single crystal) show C6F6AsF6 to be primitive rhombohedral with a0=6.60 (1) Angstroem, α=106.0 (1) deg, V=246.1 Angstreom3, Z=1, probable space group R3, and (powder data) C10F8AsF6 to be tetragonal with a0=8.27 (5) Angstroem, c0=18.57 (s) Angstroem, V=1270 Angstoem3, Z=4.Salts derived from the monocyclic perfluoro aromatics are thermally unstable but can be kept below -15 deg C.The perfluoronapthalene salts are indefinitely stable at room temperatures.All hydrolyze rapidly.The products of thermal decomposition of the hexafluoroarsenates of the monocyclic cation salts parallel the products of the attack by F-.The latter reaction products are in the molar ratios indicated by the following equations: 2C6F6+ 2F- -> C6F6+ 1,4-C6F8; 2C6F5CF3+ ->2F- -> C6F5CF3+1,3-C6F7CF3.The 1,3-C6F7CF3 isomerizes to a 1:1 mixture with 1,4-C6F7CF3 over several days in the presence of fluoro acids.Mechanisms for the formation of the dienes are discussed.
- Richardson, T. J.,Tanzella, F. L.,Bartlett, Neil
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p. 4937 - 4943
(2007/10/02)
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- FLUOROCYCLOHEXANES. PART XVI. THE SIX H-TRIFLUOROMETHYLDECAFLUORO- AND TWO OF THE 2H,4H-TRIFLUOROMETHYLNONAFLUORO-CYCLOHEXANES
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Fluorination of benzotrifluoride by cobaltic fluoride at 260-280 deg gave, besides the fluorocarbon, the six possible tridecafluoromethylcyclohexane isomers, and two 2H,4H-dodecafluorides.Of the C7HF13 compounds, only the cis-2H-, and the cis- and trans-4H-isomers could be isolated pure.The two 3H-isomers were made by pyrolysis of perfluoro(1-methyl-3-isopropylcyclohexane) in the presence of toluene.The trans-2H-isomer was made by further fluorination of one of the 2H,4H-dodecafluorides.Aqueous potash and the cis-2H-tridecafluoride gave 1-trifluoromethylnonafluorocyclohex-1-ene, which with stronger alkali hydrolysed to 1-carboxynonafluorocyclohex-1-ene.The cis- and trans- 2H and 4H-tridecafluorides were dehydrofluorinated by sodium fluoride at 320-380 deg (the cis-isomer of each pair reacted faster than the trans-: axial versus equatorial hydrogen) to give, respectively, the 1-trifluoromethylnonafluoro-ene and the 4-trifluoromethyl-isomer.The latter was isomerised to the former by sodium fluoride at 500-600 deg.The 1-CF3-ene gave hexafluoroglutaric acid on oxidation with alkaline potassium permanganate.
- Alsop, Derek J.,Burdon, James,Carter, Paul A.,Patrick, Colin R.,Tatlow, John Colin
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p. 305 - 316
(2007/10/02)
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