Dichlorodifluoromethane, reaction

Primary alkyl chlorides are fairly stable to fluorine displacement. When fluorinated, 1-chloropropane is converted to 1-chloroheptafluoropropane and 1-chloto-2-methylbutane produces 39% l-chlorononafluoro-2-methylbutane and 19% perfluoro-2-methylbutane. Secondary and tertiary alkyl chlorides can undergo 1,2-chlorine shifts to afford perfluonnated primary alkyl chlorides 2-Chloro-2-methylpropane gives l-chlorononafluoro-2-methylpropane, and three products are obtained by the fluorination of 3-chloropentane [7] (equation 1). Aerosol fluorina-tion of dichloromethane produces dichlorodifluoromethane which is isolated in 98% purity [4 (equation 2). If the molecule contains only carbon and halogens, the picture is different. Molecular beam analysis has shown that the reaction of fluorine with carbon tetrachlonde, lodotrichloromethane, or bromotrichloromethane proceeds first by abstraction of halogen to form a trichloromethyl radical [5]... 

Unfortunately, the thermodynamically favored reactions of trichlo-rolluoromethane (CFC-11) and dichlorodifluoromethane (CFC-12) with water do not proceed to a significant degree below 300 C and at least 200 atm (1 atm = 101.325 kPa) or greater [42] (equation 44) Even at 4000 atm randoimzation rather than complete hydrolysis occurs, leaving another chlorofluorocarbon, chlorotri-fluoromethane (CFC-13), which is also potentially harmful to the earth s ozone layer... 

Bromocyclopropane has been prepared by the Hunsdiecker reaction by adding silver cyclopropanecarboxylate to bromine in dichlorodifluoromethane at —29° (53% yield) or in tetrachloro-ethane at —20° to —25° (15-20% yield).3 Decomposition of the peroxide of cyclopropanecarboxylic acid in the presence of carbon tetrabromide gave bromocyclopropane in 43% yield.4 An attempt to prepare the bromide via the von Braun reaction was unsuccessful.3... 

In a dichlorodifluoromethane system, frictional wear exposed fresh metal surfaces on an aluminium compressor impellor, causing an exothermic reaction which melted much of the impellor. Later tests showed similar results, decreasing in order of intensity, with tetrafluoromethane chlorodifluoromethane bromotrifluoromethane dichlorodifluoromethane 1,2-difluorotetrafluoroethane ... 

Tellurium also forms a black dichloride and a brown dibromide usually by its reaction with dichlorodifluoromethane and trifluorobromomethane,... 

Most of the investigations into disproportionation reactions have mainly concentrated on chlorofiuoro derivatives of methane and ethane. When trichlorofluoromethane is refluxed with aluminum trichloride or aluminum tribromide, dichlorodifluoromethane and carbon tetrachloride are obtained. Dichlorofluoromethane yields chlorodifiuoromethane and chloroform chlorofiuoro derivatives of ethane and longer chain homologs exhibit a tendency towards isomerization as well as disproportionation, i.e. intramolecular halogen atom exchange. In this case, both types of reaction take place simultaneously. In other words, disproportionation of l,l,2-triehloro-1.2,2-trifiuoroethane (1) forms l,l,1.2-tetrachloro-2,2-difluoroethane (2) and... 

In principle, disproportionation can be used to produce dichlorodifluoromethane, chlorotri-fluoromethane, or carbon tetrachloride from trichlorofiuoromethanc, according to the reaction conditions selected. 

Formation of the various chlorofluoromethanes is greatly influenced by the reaction conditions. For example, dichlorodifluoromethane is the main product at reaction temperatures below 120 C. Temperatures above 120 C, on the other hand, favor the formation of chloro-... 

Similar reactions follow on after the disproportionation of carbonyl chloride fluoride into dichlorodifluoromethane and carbon dioxide, following the primary reaction. 

The halocarbons, which are not destroyed in the troposphere by reactions with hydroxyl, pass into the stratosphere where they are photo-dissociated to liberate chlorine atoms which attack ozone. Only one of them is of natural origin, methyl chloride CH3CI, but there are also several industrial products, especially carbon tetrachloride, CC14, trichlorofluo-romethane, CFC13, and dichlorodifluoromethane. Methyl chloride (Table III) has a natural marine origin (for details, see ref. 12), but it is certainly present also in the smoke produced when polyvinyl and other products containing chlorine are burnt. In addition, it is produced naturally not only in forest fires, but also in tropical agriculture based on the cultivation... 

In a dichlorodifluoromethane system, frictional wear exposed fresh metal surfaces on an aluminium compressor impellor, causing an exothermic reaction which melted much of the impellor. Later tests showed similar results, decreasing in order of intensity, with tetrafluoromethane chlorodifluoromethane bromotrifluoromethane dichlorodifluoromethane 1,2-difluorotetrafluoroethane 1,1,2-trichlorotrifluoroethane [6], In similar tests, molten aluminium dropped into liquid dichlorodifluoromethane burned incandes-cently below the liquid [7]. Aluminium bearing surfaces under load react explosively with polytrifluoroethylene greases or oils. The inactive oxide film will be removed from the metal by friction, and hot spots will initiate reaction [8]. An attempt to scale up the methylation of 2-methylpropane with chloromethane in presence of aluminium chloride and aluminium went out of control and detonated, destroying the autoclave. The preparation had been done on a smaller scale on 20 previous occasions without incident [9]. 

Atkinson, R., Hansen, D.A., Pitts Jr., J.N. (1975) Rate constants for the reaction of hydroxyl radicals with chlorodifluoromethane, dichlorodifluoromethane, trichlorofluoromethane and molecular hydrogen over temperature range 297 134 K. J. Chem. Phys. 63, 1703-1706. 

Hydrogen fluoride alone undergoes exchange reactions only with very reactive organic halides. However,. because it reacts with antimony chloride to form antimony fluoride and hydrogen chloride,34 it can be used to transform a large amount of organic halide to the fluoride with the aid of only small.amounts of antimony salts. This is the method used in industry for the preparation of dichlorodifluoromethane.34-36... 

Dichlorodifluoromethane and Trichlorofluoromethane.60 In a flask connected to an ice-cooled reflux condenser, a mixture of 2 moles of carbon tetrachloride and 1 mole of antimony trifluoride is cooled to 0°. After addition of 0.1 mole of antimony pentachloride, the mixture is allowed to warm until the reaction starts. The reaction is regulated by intermittent cooling and heating in order not to overtax the reflux condenser. The uncondensed vapors are led to a receiver cooled with solid carbon dioxide. The distillate is a mixture of CCl3F(b.p. 25°) and CCl2F2(b.p. —30°) whose composition depends on the efficiency of the dephlegmation but is usually 50-50 in a laboratory operation. At the... 

In the reaction between tellurium tetrachloride and bis[trifluoromethyl] mercury, the following compounds were also formed1 chlorine, dichlorodifluoromethane, cklorodi-fluoromethyl trifluoromethyl tellurium, and bis[chlorodifiuoromethyl tellurium... 

In the case of thiophenoxide and dichlorodifluoromethane, such a reaction forms chlorodifluoromethyl carbanion, which dissociates to difluorocarbene and chloride anion. Difluorocarbene reacts with the thiophenoxide anion to form phenylthiodifluoromethyl anion. This unstable species reacts in two ways. (1) It abstracts chlorine from another molecule of dichlorodifluoromethane and forms chlorodifluoromethyl phenyl sulfide Y. (2) It reacts with hydrogen of water to form difluoromethyl phenyl sulfide Y. Product Y can also react with two molecules of thiophenoxide anion to give bis(thiophenyl)difluoromethane Y" [SO]. 

Both the C-F and C Cl bonds are cleaved, the former always being more reactive. In the perhalomethane series, such ionic addition reactions are limited to trichlorofluoromcthane on contact with aluminum trichloride, disproportionation of dichlorodifluoromethane occurs, and chlorolrifluoromethane does not react under these conditions. On the other hand, the reactivity of haloethenes increases with the increasing number of fluorine atoms in the molecule.The alkylation has also been performed with l,l,l-trifluoroelhane. °... 

In view of the labile nature of the weak peroxide bond, the cyclization methods must be executed at low temperatures (—30 to + 10°C), but in the case of the thermally more stable derivatives, room temperature (up to -b 30°C) can be tolerated. In the silver ion-catalyzed cyclizations, solvents such as alkanes (pentane, hexane, cyclohexane) and haloalkanes (carbon tetrachloride, methylene chloride, dichlorodifluoromethane) are advantageous. In the base-catalyzed reactions, protic solvents are employed, that is, water and/or methanol and ethanol but heterogeneous solvent systems, for example, aqueous methanol and pentane, are useful. The latter conditions are designed to minimize base-catalyzed destruction of the dioxetane product by extraction into the alkane phase. The preparations of 1,2-dioxetanes via the Kopecky method are collected in Table 1. 

Dichlorodifluoromethane is prepared by the reaction of hydrogen fluoride with carbon tetrachloride in the presence of a suitable catalyst, such as polyvalent antimony. The dichlorodifluoromethane formed is further purified to remove all traces of water and hydrochloric acid as well as traces of the starting and intermediate materials. 

Dichlorodifluoromethane reacts with WO at 525 C mainly to give CO, WOF and WOCl. Small amounts of phosgene and carbonyl difluoride are also formed, but these compounds may arise from the reactions of the CO with the nickel halide films formed on the inside surfaces of the nickel reactor [2159]. 

A secondary dismutation reaction. Equation (16.5), may also occur [899], and the conditions for the synthesis of dichlorodifluoromethane by this route have been optimized, but the yield remains low [900,902,905] ... 

Bromocyclopropane (2) is obtained in moderate yield (15-20%) from the reaction of bromine with silver cyclopropanecarboxylate in tetrachloroethane. A much better yield (52-62%) is obtained in dichlorodifluoromethane as a low boiling solvent (bp — 30 °C) which considerably facilitates the isolation of bromocyclopropane. ... 

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