L-Chloro-2,2-difluoroethylene

One is the abstraction of a fluoride ion according to a ElcB elimination, which yields l-chloro-2,2-difluoroethylene. This metabohte is eliminated by exhalation. Early studies suggested that a second elimination process might be an a-elimination of a chloride ion, which produces trifluoromethylcarbene, but this was later reconsidered. It was hypothesized that a... 

Reaction of l-Chloro-l,2-difluoroethylene with Butyllithium and Carbon Dioxide... 

When l-chloro-l,2-difluoroethylene is treated consecutively with butyllithium in tetrahydrofuran (THF) and carbon dioxide, two products, F and G, are obtained after esterification with methanol. What are these products ... 

Butyllithium replaces with lithium both the hydrogen in l-chloro-1,2-difluoroethylene and the chlorine in another molecule of the same compound, in a ratio of 1 2. Subsequent treatment of the reaction mixture with carbon dioxide, water, and esterification with methanol gives a mix-... 

The product ratios observed for additions between allene and chlorotri-fluoroethylene or l,l-dichloro-2,2-difluoroethylene 126>, 85 15 in favor of the 3-chloro isomer and 95 5 for the 3,3-dichloro adduct, can t be interpreted unambiguously. If both adducts in a set stem from a common type of intermediate, then the product ratios indicate how different that intermediate is from the sorts of diradicals implicated in cydoadditions between, say, l,l-dichloro-2,2-difluoroethylene and the 2,4-hexadienes 16J. But the two adducts may arise throu gh completely independent, dissimilar reaction mechanisms. 

Cyclobutanes from the addition of 1-chloro-l-fluoroethylene to chlorotrifluoro- or tetrafluoro-ethylene, of 2-fluoropropene to tetrafluoroethylene, and of 1-chloro-2,2-difluoroethylene to vinyl fluoride or propene have been claimed to be anaesthetics. Diels-Alder addition of cyclopentadiene to acids of the type, trans-RpCHiCH COaH (Rf = CHaF, CHFa, CFs, C2F5, or n-CsFv) and a number of related esters and other derivatives, at 25 °C, results in predominant formation of adduct witii an endo fluoroalkyl group. The addition of cyclopentadiene to the 1,1-difluoroethylenes, CFalCFa, CFa CF CFs, CFa CCla, CFa C(CF3)2, CFaiCCl-CFaCl, and CFa.CFH has been recorded and the fiee-radical bromina-tion of the resulting norbomenes studied. Buta-1,3-diene and trifluorovinyl-sulphur pentafluoride yield essentially a mbcture of cis- and rmns-cyclobutanes (116), with little or no cyclohexene formation the olefin resembles perfluoropropene which yields ca. 5% of cyclohexene, in this respect. Perfluoroindene, which adds... 

Mixed polyhalides. A mixture of l-chloro-l,2-difluoroethylene, sulfur tetrafluoride, and lead dioxide heated 2 hrs. at 100° in an autoclave 1-chloro-1,1,2,2-tetrafluoroethane. Y 95.8% conversion 89.2%.—This method affords higher yields under conditions which are somewhat milder than those previously reported. F. e. s. E. R. Bissell and D. B. Fields, J. Org. Ghem. 29, 1591 (1964). 

Perfluoropropene oxide is a convenient, volatile, thermal source of difluoro-carbene, and its use in the preparation of fluorocyclopropanes has been further exemplified, perfluorinated, polyfluorinated, and hydrocarbon olefins being employed as substrates (see also p. 17) it has also been employed to convert perfluorobut-2-yne into 3,3-difluoro-l,2-bis(trifluoromethyl)cyclo-propene. Qose examination of the reaction between the epoxide and a mixture of cis- and rra .r-l-chloro-l,2-difluoroethylene at ca. 200°C has revealed that stereospecific addition of difluorocarbene takes place, but that loss of configuration can subsequently result from slow thermal isomerization of the cyclopropane product. Thermal decomposition of perfluoropropene oxide at 200 "C in the absence of a trap yields mainly perfiuorocyclo-propane and trifluoroacetyl fluoride together with tetrafluoroethylene, perfluoroisobutene oxide, perfluorobut-l-ene, and poly(difluoromethylene). 

Difluoro-l,2-dichIoroethylene. See 1,2-Di chloro-1,2-difluoroethylene in this Section... 

Ammonium perchlorate, Impurities, 3998 Azidoacetic acid, 0770 f Aziridine, Acids, 0859 Benzoyl azide, 2694 Benzyl chloroformate, 2926 1,2-Bis(difluoroamino)-/V-nitroethylamine, 0799 Bromine trioxide, 0259 2-Butanone oxime, 1649 2-Butyne-l,4-diol, 1523 Butyraldehyde oxime, 1650 Carbon, Unsaturated oils, 0297 Chlorine, Carbon disulfide, 4041 f l-Chloro-2,3-epoxypropane, Contaminants, 1158 Cyanogen chloride, 0322 Diethyl phosphorochloridate, 1675 f 1,1-Difluoroethylene, 0696... 

Polytetrafluoroethylene is the only by-product formed. Trifluoroethylene and 2-chloro- and 2-bromo-l,l-difluoroethylene all react with FIFA regiospecifically to give monohydrooxetanes 2 in 91-98 % yield. The formation of only one isomer, in sharp contrast to the earlier photochemical process [11], is consistent with an electrophilic mechanism (Sch. 2). 

Generated from HFPO, difluorocarbene reacts with a wide variety of unsaturated compounds, both fluorinated and unfluorinated. It can react stereospecifically, as illustrated with the chloro-l,2-difluoroethylenes. 

The same authors developed an original method of the synthesis of 1-(1,2,2,2-tetrafluoroethyl)-l,2,4-triazole 85 by treatment of N-(2-chloro-l,l,2-trifluoro)-1,2,4-triazole with tetramethylammonium fluoride [83]. The assumed reaction mechanism consist of several steps. In the first stage elimination of HF and the formation of 2-chloro-l,2-difluoroethylene derivative takes place. Further chlorine atom is replaced by fluorine with the formation of 1,2,2-trifluoroethylene-l,2.4-triazole. Finally addition of HF gave the final product 85. 

Disposition in the Body. Rapidly absorbed upon inhalation blood gas partition coefficient about 2.4. It accumulates in adipose tissue. About 60 to 80% of an absorbed dose is exhaled unchanged from the lungs in 24 hours and smaller amounts continue to be exhaled for several days or weeks. A variable amount is metabolised in the liver by debromination and dechlorination replacement of a fluorine atom by a methoxy group followed by glucuronic acid conjugation occurs to a limited extent. Other metabolites which have been detected in expired air and in blood are 2-chloro-1,1,1-trifluoroethane and 2-chloro-l, 1-difluoroethylene. Up to about 20% of a dose may be excreted in the urine as trifluoroacetic acid and its salts. Bromide ion is slowly excreted in the urine. 

---