Chlorodifluoromethane, reaction with

Chloroform is mainly used to produce chlorodifluoromethane (Fluorocarbon 22) by the reaction with hydrogen fluoride ... 

Fluorine can be introduced into an amino acid via this strategy. Condensation of 4,50 with chlorodifluoromethane, for example, gave 4.51. Bromination facilitated incorporation of nitrogen via reaction with phthalimide (see chapter one, section 1.1.B), and subsequent deprotection and decarboxylation gave S-(N-phthalimidoyl)-2-(difluoromethyl)penl-3-enoic acid, 4.52.27 This latter sequence was also used in a synthesis of 4-amino-2-fluorobut-2-enoic acid.28... 

HF reaction with 3-chloro-pentafluoro-l-propene (CF2=CF-CF2C1) at 200°C, catalyzed by activated carbon, yields HFP. l Hexafluoropropylene can be prepared from the catalytic degradation of fluoroform (CHF3) at 800-1000°C in a platinum-lined nickel re-actor.l l Another method is copyrolysis of fluoroform and chlorotrifluoroethylene (CF2=CFCl),f l or chlorodifluoromethane and l-chloro-1,2,2,2-tetrafluoroethane (CHClFCFg), giving good yields of HFP. 

In the first step, chloroform is converted into chlorodifluoromethane by catalytic vapor phase fluorination reaction with anhydrous hydrogen fluoride and in the second step, chlorodifluoromethane is subjected to a noncatalytic gas phase pyrolysis at temperature 590-900°C and at atmospheric or subat-mospheric pressures to obtain tetrafluoroethylene in about 95% yield. 

Difluoroethanol is prepared by the mercuric oxide cataly2ed hydrolysis of 2-bromo-l,l-difluoroethane with carboxyHc acid esters and alkaH metal hydroxides ia water (27). Its chemical reactions are similar to those of most alcohols. It can be oxidi2ed to difluoroacetic acid [381-73-7] (28) it forms alkoxides with alkaH and alkaline-earth metals (29) with alkoxides of other alcohols it forms mixed ethers such as 2,2-difluoroethyl methyl ether [461-57-4], bp 47°C, or 2,2-difluoroethyl ethyl ether [82907-09-3], bp 66°C (29). 2,2-Difluoroethyl difluoromethyl ether [32778-16-8], made from the alcohol and chlorodifluoromethane ia aqueous base, has been iavestigated as an inhalation anesthetic (30,31) as have several ethers made by addition of the alcohol to various fluoroalkenes (32,33). Methacrylate esters of the alcohol are useful as a sheathing material for polymers ia optical appHcations (34). The alcohol has also been reported to be useful as a working fluid ia heat pumps (35). The alcohol is available ia research quantities for ca 6/g (1992). 

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 ... 

The explosive phenomena produced by contact of liquefied gases with water were studied. Chlorodifluoromethane produced explosions when the liquid-water temperature differential exceeded 92°C, and propene did so at differentials of 96-109°C. Liquid propane did, but ethylene did not, produce explosions under the conditions studied [1], The previous literature on superheated vapour explosions has been critically reviewed, and new experimental work shows the phenomenon to be more widespread than had been thought previously. The explosions may be quite violent, and mixtures of liquefied gases may produce overpressures above 7 bar [2], Alternative explanations involve detonation driven by phase changes [3,4] and do not involve chemical reactions. Explosive phase transitions from superheated liquid to vapour have also been induced in chlorodifluoromethane by 1.0 J pulsed ruby laser irradiation. Metastable superheated states (of 25°C) achieved lasted some 50 ms, the expected detonation pressure being 4-5 bar [5], See LIQUEFIED NATURAL GAS, SUPERHEATED LIQUIDS, VAPOUR EXPLOSIONS... 

A direct route to thiocarbonyl fluoride is reaction of chlorodifluoromethane with sulfur in a hot tube at 700-900° C (52). This reaction gives very high yields and is amenable to preparation of... 

Reaction of 13C-labeled chloroform with this reagent for 3 hours at O C gives 13CHFC12 as the major product. Under modified conditions, when 13CHC13 is added to the fluorinating agent [4 g of solid antimony(III) fluoride and 4 g of liquid antimony(V) chloride] and is warmed to 40 °C, the volatile product that distills off at — 90°C is 13C-labeled chlorodifluoromethane (80% conversion).73... 

The reaction of chlorodifluoromethane with alkoxide ions generated in low concentration from halide ions and epoxides [28, 29] is an interesting, higher temperature method that gives good to excellent yields of gem-difluorocyclo-propanes from just moderately nucleophilic olefins (equation 9)... 

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. 

Reaction of Pentafluorophenol with Chlorodifluoromethane and Sodium Hydroxide... 

In a 500-mL. round-bottomed, four-necked glass reactor, fitted with an efllcient mechanical stirrer, thermometer. sintered gas inlet, and a condenser (cooled to — 40 C). was charged the benzenethiol 7 (0.2 mol), finely crushed NaOH (20 g, 0.5 mol). tris[2-(2-methoxyethoxy)ethyl]amine (TDA-I 3.2 g, 0.01 mol), and solvent (TCB or toluene. 200 mL). This mixture was vigorously stirred while chlorodifluoromethane (8) was bubbled through the solution. A noticeable exothermy was observed during the first few min. Then, the medium was heated up to the desired temperature (vide supra) and maintained there for the time indicated, whilst passage ofS was continued. The progress of the reaction was monitored by GC analysis. 

Brown ei al. now find that tri-/i-butylcarbinol is obtained in essentially quantitative yield by the reaction of tri-n-butylborane with chlorodifluoromethane (or other tri-substituted methanes) under the influence of lithium triethylcarboxide (equation 2). 

One of the best-known thermal reactions of fluorine compounds is the pyrolysis of chlorodifluoromethane to tetrafluoroethylene as used in the production of Teflon polymer. This reaction was described by Park et in 1947, and Nor-ton" in 1957 reported an activation energy of 49 kcal.mole for the decomposition over silica at 425-525 °C. More recently, Gozzo and Patrick have made a kinetic study of the process using a helium flow system at 670-750 °C with a surface conditioned platinum tubular reactor. HCl is found to retard the raction and the following mechanism has been proposed... 

A reaction of haloforms with a base, which generates dihalocarbenes (a-elimination) and their addition to alkenes is an efficient method for the preparation of 1,1-dihalocyclopropanes, with the exception of 1,1-difluoro derivatives (Houben-Weyl, Vol.E19b, pp 1464-1466). When chlorodifluoromethane and an alkene are treated with methyllithium, potassium tcrt-butox-ide, powdered sodium hydroxide in tetraglyme or a concentrated aqueous solution of alkali metal hydroxide and a phase-transfer catalyst, the expected 1,1-difluorocyclopropanes are formed in low yields. Comparable low yields of these products result, if dichlorodi-fluoromethane and an alkene are treated with methyllithium. " The main products formed are those that result from reaction of difluorocarbene (carbenoid), and its precursor, with the base or the solvent present in the system (for examples, see refs 10-12). Therefore, the reaction of chlorodifluoromethane with base and an alkene lacks preparative value. The difficulties mentioned above are circumvented in the method using chlorodifluoromethane, oxirane (or chloromethyloxirane), with tetraalkylammonium halide as a catalyst and an alkene (Houben-eyl, Vol. 4/3, p 380 and Vol. E19b, pp 1468-1469). 

Chang JS, Kaufman F. 1977. Kinetics ofthe reactions of hydroxyl radicals with some halocarbons Dichlorofluoromethane, chlorodifluoromethane, trichloroethane, trichloroethylene, and tetrachloroethylene. J Chem Phys 66 4989-4994. 

This is prepared by the reaction of N, N -dibenzylidenelysine methyl ester (124) with chlorodifluoromethane (HCCIF2) in the presence of lithium diisopropy-lamide. The resulting ester is hydrolysed with HCl to get DL-DFMO, which is isolated as its monohydrochloride, monohydrate [80]. 

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