Water hexafluorobenzene

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. 

Interestingly, in fluorinated solvents where the solubility of the reagents is not compromised, for example hexafluorobenzene, the rate of reaction is not increased (Figure 7.2). This implies that there is an inverse relationship between solubility of reagents and the rate of reaction, and that this relationship may be exploited by the use of either water or suitable perfluorinated solvents. 

Figure 3. Effect of water on the reaction of hexafluorobenzene and bisphenol-A in chlorobenzene in the presence of 18 crown-6 catalyst. Products of the catalyzed reaction were oligomeric materials. No reaction is observed under the experimental conditions in the absence of the 18-crown--6 catalyst. (Reproduced with permission from reference 14, Copyright 1985 John Wiley.)...

All of these solvents (neat) and all possible 1 1 mixtures (19X19) were tested for their ability to completely solubilize each of the 5 peptides at a level of 1 mg/ml. Each neat solvent and 1 1 mixture was subjected to 5 independent variations no additives, added 1% trifluoroacetic acid (TEA), added 2% pyridine, added 1% TEA + 5% water, added 2% pyridine + 5% water. Each solvent system was tested for its ability to solubilize the peptides both upon prolonged incubation (48 hrs) at room temperature and also when warmed on a hot water bath (2 minutes, 90 degrees). A number of less systematic tests were conducted involving mixtures including the following solvents formic acid, TEA, N-methylpyrollidinone (NMP), hexafluorobenzene (HEB). 

Results of Calculatious. The root-mean-square deviations (rmsd) of the calculated pressures with respect to the experimental ones are listed in Tables 3 and 4. The comparison of the rmsd for alcohol/water mixtures indicates that the new equations provide the best performances for 29 VLF and NRTL for 5 sets. A similar conclusion was reached for the systems containing benzene, hexafluorobenzene, toluene, and cyclohexane the new equations provide the best performances for 7 sets, and the new equations and the NRTL provide almost the same results for 2 sets. 

A theoretical calculation suggests that the interactions of water molecules with hexaflu-orobenzene and benzene are totally different. A water molecule approaches the center of hexafluorobenzene through the oxygen as Lewis base, while with benzene the hydrogen acts as a Bronsted acid (Scheme 1.25) [15, 16]. Of particular interest is the finding that ab initio calculations show that the water molecule in a 1 1 mixture of hexafluorobenzene and benzene... 

Preparative Method aqueous Hydrofluoric Acid is passed through an Amberlite IRA 410 OH column, followed by an aqueous solution of Tetrabutylammonium Bromide. After the resin is washed with water, the combined water fractions are repeatedly evaporated until no water is present. Tetrahutylammonium fluoride is collected as an oil in quantitative 3neld. TBAF-a H20 aqueous hydrofluoric acid is passed through an Amberlite IRA 410 OH column, followed by an aqueous solution of tetra- -butylammonium bromide. After the resin is washed with water, the combined water Iractions are repeatedly evaporated until no water is present. Tetrabutylanunonium fluoride is collected as an oil in quantitative yield. The hydrofluoric acid method has been described most recently by Kumar. TBAFanh under nitrogen, hexafluorobenzene is added to a cold (—50 °C) THF solution of tetra-n-butylanunonium cyanide. The highly colored solution is stirred for 4 h at —15 °C, cooled to —60 °C, and filtered. The resulting colorless solid is washed with cold THF and the residual solvent is removed in vacuo to yield anhydrous TBAF (60%). ... 

Calcium, Magnesium, and Mercury.—Complete reduction to benzene results when hexafluorobenzene saturated with water reacts with atomic calcium. Pentafluorophenylmagnesium compounds may be prepared by reaction of ethylmagnesium halide with CjFbX (X = H, Cl, Br, or 1). Both bromines... 

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