- Hydrogenolysis of carbon-chlorine bonds in carbon tetrachloride and trichlorofluoromethane in the presence of catalytic quantities of tris(triphenylphosphine) ruthenium(II) dichloride
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The hydrogenolysis of carbon tetrachloride to chloroform, and of trichlorofluoromethane to hydrodichlorofluoromethane, are catalyzed by the complexes RuCl2(PPh3)3 and RuCl2(dppe)2.The conversion of carbon tetrachloride into chloroform is more complete than the conversion of trichlorofluoromethane into hydrodichlorofluoromethane.Key words: Ruthenium; Hydrogenolysis; Carbon-chlorine bonds; Homogeneous catalysis
- Xie, Shaofeng,Georgiev, Emil M.,Roundhill, D. Max,Troev, Koljo
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- KINETICS OF CHLOROFORM FLUORINATION BY HF CATALYZED BY ANTIMONY PENTACHLORIDE
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It is shown that SbCl4F can be considered as the main fluorinating agent when HF and SbCl5 are used in fluorination with an HF/SbCl5 ratio of 1:1.A very simple way for preparing SbCl4F is described in the paper.Kinetic runs, performed in batches using both SbCl4F and HF+SbCl5 as fluorinating agents, allowed identification of the reaction pattern for the chloroform fluorination.Fluorination proceeds through four consecutive steps in which the first and the second are fast and reversible reactions, corresponding to the fluorine-chlorine exchange between HF/SbCl5 and SbCl4F/ChCl3 respectively.The main product, CHClF2 is formed in the third reaction.The last step to CHF3 is very slow.Assuming the formation of CHClF2 as reference, the relative reaction rates for the steps are: 150/7/1/0.03. Kinetic equations and parameters obtained by fitting batch runs have also been verified by interpreting experiments performed under steady state conditions.The kinetic model, employed for elaborating both batch and continuous runs, takes into account also the vapour-liquid equilibria for reactant and products.Suggestions are made on the reaction mechanisms.
- Santacesaria, E.,Serio, M. Di,Basile, G.,Carra, S.
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- Chain photoreduction of CCl3F induced by TiO2 particles
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Fluorotrichloromethane (CFC 11) is dehalogenated through a reductive chain reaction upon illumination of aqueous, air-free suspensions of TiO2 particles in the presence of formate ions. The reduction takes place with large photonic efficiencies at pH a?￥ 5 even at high photon fluxes, producing mainly Cl- and dichlorofluoromethane (HCFC 21), while F- is only a minor byproduct. In the proposed mechanism .CO2- and .CCl2F radicals are the chain carriers, Cl- as well as HCFC 21 result from propagation steps, and cross-termination of the chain carriers forms F-. Simple steady-state assumptions, that regard propagations as the dominant steps, yield kinetic equations consistent with the data of the initial fast Cl- formation step. The subsequent evolution of rates and postirradiation effects are consequences of the slow removal of electrons from the semiconductor.
- Calhoun,Winkelmann,Mills
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- A combination of three fluoromethane cracking process for preparing
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The invention provides a technique for preparing monochlorodifluoromethane by decomposing trifluoromethane. The technique comprises the steps of: feeding the raw materials trifluoromethane and methane chloride into a reactor filled with a catalyst in the mol ratio of 0.1-10, and carrying out a decomposition reaction at a temperature ranging from 150 to 350 DEG C for 3-30 seconds to obtain a mixture of trifluoromethane, methane chloride, dichloromonofluoromethane and monochlorodifluoromethane; obtaining monochlorodifluoromethane directly through separation, reacting dichloromonofluoromethane separated out with hydrogen fluoride to produce monochlorodifluoromethane, and separating out and recovering trifluoromethane and methane chloride in the mixture as the reaction mixture continuously. The method has the advantage that the harm on the environment caused by trifluoromethane emission is greatly avoided.
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Paragraph 0025; 0026; 0030
(2017/02/24)
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- Interaction of trichloromethane and tetrachloromethane with nitrogen trifluoride
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Interaction of nitrogen trifluoride with trichloromethane and tetrachloromethane at temperatures in the range from 20 to 200°C and pressures of up to 6.0 MPa in the gas and liquid phases was studied.
- Mukhortov,Pashkevich,Blinov,Kambur,Kambur,Petrov,Kurapova
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body text
p. 420 - 426
(2011/08/04)
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- Process for the manufacture of hydrochlorofluorocarbons using trifluoromethane as fluorinating agent
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The present invention provides a process for the manufacture of hydrochlorofluorocarbons comprising treating a hydrocarbon substituted with one or more chlorine atoms and optionally one or more fluorine atoms under elevated temperature with GHF3.
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Page/Page column 5-6
(2010/04/25)
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- PROCESS FOR THE MANUFACTURE OF CHLORODIFLUOROMETHANE
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A process is disclosed for the manufacture of CHClF2 which involves contacting CHCl3, HF and pentavalent antimony catalyst in the liquid phase; passing reactor vapor effluent to a reflux column to produce a reflux column vapor effluent of CHClF2 and HCl; passing the reflux column vapor effluent to a condenser to produce a condenser liquid effluent of CHClF2 and a condenser vapor effluent of CHClF2 and HCl; passing the condenser liquid effluent to the reflux column upper end; and recovering CHClF2 from the condenser vapor effluent. The concentration of CHCl2F and CHF3 in the condenser vapor effluent is controlled by: (i) controlling the temperature at a point within the lower third of the theoretical stages of the reflux column by controlling the heat input to the reactor liquid phase; (ii) controlling the pressure in the reactor, reflux column and condenser by controlling the rate at which the condenser vapor effluent is removed from the condenser; (iii) maintaining the reflux ratio of the condenser at a substantially constant value; and (iv) maintaining the reactor liquid phase at substantially the maximum mass that does not result in entrainment or flooding of the reflux column. Also disclosed is CHClF2 which is a product of this process. Also disclosed is a refrigerant comprising CHClF2 and a method for its manufacture, a polymer foam blowing blend comprising CHClF2 and a method for its manufacture, fluoromonomers tetrafluoroethylene and hexafluoropropylene produced by using CHClF2 and a method for their manufacture, and a fluoropolymer produced by using CHClF2 as a fluoromonomer precursor and a method for its manufacture; all involving the manufacture of CHClF2 in accordance with the above process.
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Page/Page column 20-22
(2008/06/13)
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- Fluorinated phosphonium ylides: Versatile in situ Wittig intermediates in the synthesis of hydrofluorocarbons
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A simple and convenient technique has been developed for the synthesis, characterisation and isolation of hydrofluoro/hydrohalofluorocarbons such as chlorodifluoromethane (CF2ClH), difluoromethane (CF2H2), bromodifluoromethane (CF2BrH) and dibromofluoromethane (CFBr2H) as possible chlorofluorocarbon (CFC) alternatives. The Wittig reaction of carbonyl compounds with in situ generated triphenylphosphonium ylides in DMF forms terminal fluoroolefins. However, in the absence of the carbonyl moiety these ylides undergo decomposition. The high reactivity of fluoromethylene triphenylphosphonium ylides in DMF in the absence of the carbonyl moiety has been exploited for the first time to design the synthesis of hydrofluorocarbons.
- Bhadury, Pinaki S.,Palit, Meehir,Sharma, Mamta,Raza, Syed K.,Jaiswal, Devendra K.
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- The influence of redox potential on the degradation of halogenated methanes
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To determine the influence of redox potential on the reaction mechanism and to quantify kinetics of the dechlorination by digester sludge, the test compounds trichlorofluoromethane (CFCl3), carbon tetrachloride (CCl4), and chloroform (CHCl3) were incubated in the presence of sludge and variable concentrations of reducing agent. Different sources of dehalogenation were examined, including live sludge and heat-killed sludge, and abiotic mechanisms were quantified in the absence of sludge. Batch incubations were done under redox conditions ranging from +534 to -348 mV. The highest rates for the dehalogenation of the three compounds were observed at -348 mV. The dechlorination rate of all the compounds by the heat-resistant catalysts was approximately twofold higher than the live treatments. It was proposed that the higher degradation rates by heat-killed sludge were due to the absence of physical barriers such as cell wall and cell membranes. There was no abiotic dechlorination of CFCl3, whereas CCl4 and CHCl3 were both reduced in the absence of sludge catalyst by Ti (III) citrate at ≥2.5 mM. The degradation pathways of CFCl3 and CHCl3 appeared to be only partially reductive since the production of reduced metabolites was low in comparison with the total amount of original halogenated compounds degraded. For CFCl3, the partial reductive degradation implied that different intra- and extra-cellular pathways were concurrent. The Gibbs free energy and the redox potential for the dehalogenation reactions utilizing Ti (III) citrate and acetate as electron donors are reported here for the first time.
- Olivas, Yolanda,Dolfing, Jan,Smith, Geoffrey B.
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p. 493 - 499
(2007/10/03)
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- Generation of 'naked' fluoride ions in unprecedentedly high concentrations from a fluoropalladium complex
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An F-/Cl- ligand exchange in the stable organopalladium fluoro complex 1 generates naked fluoride ions in unusually high concentrations. The released Freadily fluorinates dichloromethane under exceedingly mild conditions and deprotonates chloroform to produce dichlorocarbene.
- Grushin, Vladimir V.
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p. 994 - 996
(2007/10/03)
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- Substituent effects and threshold energies for the unimolecular elimination of HCl (DCl) and HF (DF) from chemically activated CFCl2CH3 and CFCl2CD3
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Combination of CFCl2 and methyl-d0 and -d3 radicals form CFCl2CH3-d0 and -d3 with 100 and 101 kcal/mol of internal energy, respectively. An upper limit for the rate constant ratio of disproportionation to combination, kd/kc, for Cl transfer is 0.07 ± 0.03 for collision of two CFCl2 radicals and 0.015 ± 0.005 for CH3 and CFCl2 radicals. The chemically activated CFCl2CH3 undergoes 1,2-dehydrochlorination and 1,2-dehydrofluorination with rate constants of 3.9 × 109 and 4.9 × 107 s-1, respectively. For CFCl2CD3 the rate constants are 8.7 × 108 s-1 for loss of DCl and 1.1 × 107 s-1 for DF. The kinetic isotope effect is 4.4 ± 0.9 for HCl/DCl and appears to be identical for HF/DF. Threshold energies are 54 kcal/mol for loss of HCl and 68 kcal/mol for HF; the E0's for the deuterated channels are 1.4 kcal/mol higher. Comparison of these threshold energies with other haloethanes suggests that for HF and HCl elimination the transition states are developing charges of different signs on the carbon containing the departing halogen and that chlorine and fluorine substituents exert similar inductive effects.
- McDoniel, J. Bridget,Holmes, Bert E.
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p. 3044 - 3050
(2007/10/03)
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- Selective fluorination of dichloromethane by highest oxidation state transition-metal oxide fluorides
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In contrast to the reactivity of high oxidation state binary transition-metal fluorides with organic solvents, many transition-metal oxide fluorides do not react with CH2Cl2. Only the highest oxidation state species react, at temperatures below room temperature, via Cl-F exchange with > 90% selectivity, affording unstable high oxidation state chloro complexes which decompose to chlorine and lower oxidation state species.
- Holloway, John H.,Hope, Eric G.,Townson, Paul J.,Powell, Richard L.
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p. 105 - 107
(2007/10/03)
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- High Oxidation State Binary Transition Metal Fluorides as Selective Fluorinating Agents
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High oxidation state transition metal fluorides are selective fluorinating agents for dichloromethane, those with d0 electronic configurations undergo hydrogen-fluorine exchange and metal reduction, while dn species undergo chlorine-
- Dukat, Wolfgang W.,Holloway, John H.,Hope, Eric G.,Rieland, Matthias R.,Townson, Paul J.,Powell, Richard L.
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p. 1429 - 1430
(2007/10/02)
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- The reactions of xenon difluoride with "inert" solvents
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The reactions of XeF2 with a variety of organic solvents are dscribed.XeF2 is found to undergo both hydrogen-and chlorine-fluorine exchange over a relatively short timescale with chloroform, dichloromethane and dibromomethane.XeF2 reacts very slowly with tetrachloromethane and fluorotrichloromethane, although the addition of a catalitic amount of Hf increases the rate of reaction considerably.XeF2 dissolves in acetonitrile with negligible reaction to the extent of 2.25 mol kg-1.
- Dukat, Wolfgang W.,Holloway, John H.,Hope, Eric G.,Townson, Paul J.,Powell, Richard L.
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p. 293 - 296
(2007/10/02)
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- REACTIONS OF CHLORINE MONOFLUORIDE. SUBSTITUTION OF CHLORINE ATOMS BY FLUORINE IN CHLORINE-SUBSTITUTED ALKANES AND ESTERS
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In anhydrous hydrogen fluoride under mild conditions chlorine monofluoride selectively substitutes the chlorine atoms in chlorine-substituted alkanes and esters by fluorine with the formation of high yields of the corresponding fluorides.The presence of an alkoxycarbonyl group or difluoromethylene group at the α position to the CHCl group deactivates the chlorine atom, and substitution by fluorine does not occur.In chloroalkanes, from which elimination of the chloride ion leads to sufficiently stable carbocations, substitution by fluorine can be realized in the absence of hydrogen fluoride at temperatures between -20 and -60 deg C.The fluorinating capacity of chlorine monofluoride is increased in the presence of catalytic amounts (3-5percent) of antimony pentachloride.Here the reaction is less selective than in hydrogen fluoride.In certain cases substitution is accompanied by hydride transfers.
- Chuvatkin, N. N.,Panteleeva, I. Yu.,Boguslavskaya, L. S.
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p. 821 - 827
(2007/10/02)
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- PREPARATION OF HALO-F-METHANES VIA POTASSIUM FLUORIDE-HALOGEN CLEAVAGE OF HALO-F-METHYLPHOSPHONIUM SALTS
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Treatment of halo-F-methylphosphonium salts with potassium fluoride and halogen (I2, Br2, ICl, IBr) gives modest yields of halo-F-methanes.This method of preparation augments the classical Hunsdiecker approach to these materials.
- Burton, D. J.,Shin-Ya, S.,Kesling, H.S.
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