- REACTIONS IN ANHYDROUS HYDROGEN FLUORIDE
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Anhydrous hydrogen fluoride serves as an excellent agent for introducing fluorine into organic compounds, as a solvent and a catalyst with Friedel-Crafts activity.A number of chlorine/fluorine exchange reactions which occur in HF are described, some of which have involved surprising rearrangement processes.New reactions, in which the catalytic action of hydrogen fluoride are utilized, are also discussed.
- Baasner, B.,Klauke, E.
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- Examples of catalytic and selective routes for fluorinated building blocks
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Examples are presented for the catalytic fluorination of chlorinated starting materials in order to produce building blocks or HFCs. The fluorination of CF3CH2Cl, of CCl2=CCl2, of trichloromethoxylbenzenes and trichloromethoxybenzene involving nucleophilic substitution are reported. In all cases, HF was the fluorinating agent. Depending on the chlorinated substrate and the degree of fluorination required, liquid- or gas-phase processes were involved. Usually, catalysts were SbCl 5 in liquid phase and chromium oxide in gas phase. In the presence of SbCl5, at 90 °C under an initial pressure of 10 bar, the fluorination of CCl2=CCl2 leads mainly to the formation of CClF2CHCl2, and the active catalyst is an antimony mixed halide (SbCl3F2). In the same way, the presence of SbCl5 favored the formation of 1-trifluoromethyl-3- trichloromethylbenzene from bis-1,3-trichloromethylbenzene at low temperature (50 °C) and in the presence of a low amount of HF. Moreover, trichloromethoxybenzene was totally transformed into trifluoromethoxybenzene. At 380 °C and at atmospheric pressure, the transformation of CF 3CH2Cl into CF3CH2F was favored over chromium oxide-based catalyst modified by zinc (corresponding to a (Zn/Zn + Cr) molar ratio of 0.22).
- Brunet, Sylvette
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p. 1067 - 1071
(2014/11/27)
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- Preparation of trichloromethyl-trifluoro methyl-benzenes
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A process for preparing a xylene which is fluorinated and chlorinated in the side chain, having the formula STR1 wherein X represents hydrogen or fluorine and Y represents hydrogen or chlorine and R1 and R2 are identical or different and represent hydrogen, halogen, a trifluoromethyl or trichloromethyl group or an aliphatic or aromatic radical and R1 and R2 can be bonded via hydrocarbon members to form an aromatic ring, By contacting a compound of the formula STR2 wherein X, R1 and R2 have the above-mentioned meanings, WITH A COMPOUND OF THE FORMULA STR3 wherein X, R1 and R2 have the above-mentioned meanings, in the presence of a halogen transfer catalyst at elevated temperature.
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- Fluorination of trichloromethyl groups
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A process for the preparation of a trichloromethyl-trifluoromethylbenzene of the formula STR1 wherein R1 and R2 are independently selected from the group consisting of hydrogen, fluorine, chlorine and bromine which comprises contacting a bis-(trichloromethyl)-benzene of the formula STR2 wherein R1 and R2 have the previously assigned significance with less than 6 mols of anhydrous hydrogen fluoride in the presence of a halogen transfer catalyst.
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