Trifluoroethane, reaction

Photochlorination of tetrachloroethylene, observed by Faraday, yields hexachloroethane [67-72-1]. Reaction with aluminum bromide at 100°C forms a mixture of bromotrichloroethane and dibromodichloroethane [75-81-0] (6). Reaction with bromine results in an equiUbrium mixture of tetrabromoethylene [79-28-7] and tetrachloroethylene. Tetrachloroethylene reacts with a mixture of hydrogen fluoride and chlorine at 225—400°C in the presence of zirconium fluoride catalyst to yield l,2,2-trichloro-l,l,2-trifluoroethane [76-13-1] (CFG 113) (7). 

Difluoromethoxy-2-chloro-l,l,l-trifluoroethane and potassium fluoride produce 2-difluoromethoxy-1,1,1,2-tetrafluoroethane [50] The yield of the latter reaction is improved by adding a phase transfer catalyst or crown ether, tetra-methylammonium chlonde, tetrabutylammonium chloride, or 18-crown-6 with a solvent like sulfolane can be used for this purpose [5/] (equation 32)... 

A nonconventional synthesis of the known inhalation anaesthetic, 2-bromo-2 chloro-l,l,l-trifluoroethane (Halothane), based on the reaction of ethyl 1,2 di bromo-1,2-dicliloroethyl ether with anhydrous hydrogen fluoride and sulfur tetrafluoride, has been patented The reaction presumably involves cleavage of the ether linkage, followed by fluorination of the intermediate bromochloroacetyl halide with sulfur tetrafluoride, ethyl halides are the by-products [2] (equation 2)... 

Under anaerobic conditions, various reactions can occur, and the following are illustrative (a) trichlorofluoromethane -> carbon monoxide (b) hexachloroethane tetrachlo-roethene (c) l,l,l-trichloro-2,2,2-trifluoroethane l,l-dichloro-2,2-difluoroethene (Hur et al. 1994). 

A 1-1., four-necked, round-bottomed flask equipped with reflux condenser, sealed stirrer, thermometer, and solid addition funnel and protected from atmospheric moisture with a Drierite guard tube is carefully dried and flushed with a dry inert gas (Note I). The flask is charged with 453 g. (3.1 moles) of silver difluoride (Note 2) and 500 ml. of l,l,2-trichloro-l,2,2-trifluoroethane (Note 3), and phenyl disulfide (100 g., 0.458 mole) (Note 4) is weighed into the solid addition funnel. The stirrer is started, and phenyl disulfide is added to the slurry in small portions. An exothermic reaction occurs, and after the addition of several portions the reaction mixture reaches a temperature of 40° (Note 5). By intermittent use of a cooling bath and by adjusting the rate of addition of the disulfide, the reaction temperature may be maintained between 35° and 40°. The addition of the phenyl disulfide requires 45-60 minutes. On completion of the addition the suspension of black silver difluoride has been converted to yellow silver monofluoride, and the exothermic reaction gradually subsides. The reaction mixture is stirred for an additional 15-30 minutes without external cooling and then quickly heated to reflux. 

Table 34 Calculated KIEs at various positions for the proton transfer transition state for the Elcb(irr) reaction between hydroxide ion and 1,1,1 -trifluoroethane at 20°C. ...

Using the same experimental approach, a family of enantiomerically pure oxonium ions, i.e., O-protonated 1-aryl-l-methoxyethanes (aryl = 4-methylphenyl ((5 )-49) 4-chlorophenyl ((5)-50) 3-(a,a,a-trifluoromethyl)phenyl ((5)-51) 4-(a,a,a-trifluoromethyl)phenyl ((S)-52) 1,2,3,4,5- pentafluorophenyl ((/f)-53)) and 1-phenyl-l-methoxy-2,2,2-trifluoroethane ((l )-54), has been generated in the gas phase by (CH3)2Cl -methylation of the corresponding l-arylethanols. ° Some information on their reaction dynamics was obtained from a detailed kinetic study of their inversion of configuration and dissociation. Figs. 23 and 24 report respectively the Arrhenius plots of and fc iss for all the selected alcohols, together with (/f)-40) of Scheme 23. The relevant linear curves obey the equations reported in Tables 23 and 24, respectively. The corresponding activation parameters were calculated from the transition-state theory. 

The reactivity of acyl radicals inside and outside the solvent cage has been a matter of discussion. It has been postulated that aryloxy and acyl radicals could disproportionate within the cage to give phenol (or naphthol) and ketene (37) but the results are not conclusive (Scheme 14). On the one hand, photolysis of 1-naphthyl acetate in a solvent without abstractable H-like Freon 113 (1,1,2-trichl-oro-l,2,2-trifluoroethane) yields low amounts of 1-naphthol (< 0.1%) in comparison with the same reaction in acetonitrile (7%) [50]. This reveals that dispropor-... 

Chloro-2.2-difluorovinylzinc chloride 59 opens the access to a range of fluorine-containing molecules via cross-coupling reactions. Normant and coworkers have prepared this zinc reagent by the deprotonation of l-chloro-2,2-difluoroethene 60 and transmetalation ". These two steps can be combined in one and the lithiation of 60 with w c-BuLi in the presence of ZnCB provides the corresponding dialkylzinc 61 as a colorless clear solution . Percy and coworkers and Burton and Anilkumar reported that the deprotonation of l-chloro-2,2,2-trifluoroethane 62 produces, after elimination and... 

Recently, 1,1-dichlorotrifluoroethyl zinc chloride [60,61] has received significant attention due to the readily available starting material, 1,1,1-trichloro-trifluoroethane and potential industrial applications. This zinc reagent undergoes a variety of functionalization reactions, particularly addition to aldehydes [62,63] (Scheme 22). 

The interaction of xenon difluoride with ethene at room temperature was investigated soon after xenon difluoride was discovered.26 The reaction mixture contained 1,2-difluoroethane (45%), 1,1-difluoroethane (35%) and 1,1,2-trifluoroethane (20%). 

The direction of iodine monofluoride addition to hexafluoropropene and, 1,1-di-fluoroethene suggests an electrophilic reaction mechanism. However, chlorotrifluoroethene gives a mixture of isomers both with iodine monofluoridc and with bromine monofluoride .1 0 The reactions of fluoroalkenes with bromine monofluoride proceed too quickly and for this reason they are conducted in l,l,2-trichloro-l,2,2-trifluoroethane though this hampers the isolation of addition products. 

The phenomenon of halotropism occurs in the reaction of tribromoacetic, 2-bromopropanoic and fnm -3,4-dibromocyclopentane-l-carboxylic acid with sulfur tetrafluoride. Tribromoacetic acid reacts at 25 C to give l,l,2-tribromo-l,2,2-trifluoroethane (6a) in 95% yield, while the other two acids give mixtures of trifluoromethyl derivatives 7 and rearranged 1,1,2-tri-fluoroalkanes6.110 The halogen shifts confirm the carbocationic mechanism of the fluorination reaction (vide supra). 

C. For example, reaction of 2-oxopropanoic acid with sulfur tetrafluoridc (20°C, 12 h) gives 1,1,1-trifluoroethane (25) quantitatively.117... 

All three compounds (WF6 and MoF6 are best) will bring about a reaction (not a fluorination) that may have synthetic utility at 0CC in l,l,2-trichloro-l,2,2-trifluoroethane (Freon 113) or chloroform they will cleave N,TV-dimethyl- and N-tosylhydrazones and oximes back to the parent carbonyl compounds12,14 (UF6 converts any first-formed aldehydes into acid fluorides1213). All three hexafluorides will convert1215 tertiary amines into carbonyl compounds and carboxylic acids into acid fluorides.16 They also dope polyacetylene to the metallic regime.17... 

Uranium(VI) fluoride in l,l,2-trichloro-l,2,2-trifluoroethane at 0°C oxidizes12 aldehydes to acid fluorides in moderate yields (e.g., heptanoyl fluoride from heptaldehyde in 47% yield, benzoyl fluoride from benzaldehyde in 40% yield) benzaldehyde gives methyl benzoate and benzaldehyde dimethyl acetal when the reaction mixture is worked up by quenching with methanol.13... 

The effect of ultrasound on the course of the Balz-Schiemann reaction has been studied using benzenediazonium tetrafluoroborate.263 In the presence of triethylamine trihydrofluoride in l,l,2-trichloro-l,2,2-trifluoroethane (Freon 113), fluorobenzene is formed in a 92-95% yield under 17 kHz sonication for 8 hours at 40 °C. Without ultrasound, only an 85 % yield is obtained after a reaction time of 16 hours. 

Male Fischer 344 rats were exposed by inhalation to 1% 2-chloro-1,1,1 -trifluoroethane for 2 h and then urine was collected for 24 h. Urinary metabolites identified by 19F nuclear magnetic resonance and gas chromatography/mass spectrometry were 2,2,2-trifluoroethyl glucuronide (16%), trifluoroacetic acid (14%), trifluoroacetaldehyde hydrate (26%), trifluoroacetaldehyde-urea adduct (40%) and inorganic fluoride (3%). A minor, unidentified metabolite was also detected. No covalent binding of fluorine-containing metabolites was observed in the liver and kidney from the exposed rats (Yin et al., 1995). In-vitro incubation of 2-chloro-1,1,1-trifluoroethane with rat liver microsomes and an NADPH-generating system has been shown to involve a dechlorination reaction (Salmon et al., 1981) that produced trifluoroacetaldehyde hydrate as the only metabolite (Yin et al., 1995). 

A series of halogenated ethanes 1 containing the trifluoromethyl group has been oxidized under various conditions.5-7 When water is present in the reaction mixture, the acid 3 is usually formed during the reaction when water is absent, the acid halide 2 formed can be hydrolyzed in a trap with water. Trifluoroacetaldehyde hydrate 4 is formed6 as a minor product in addition to the acid when 2-chloro-l,l,l-trifluoroethane is treated with oxygen and chlorine under UV irradiation with subsequent reflux of the mixture with hydrogen peroxide. 

As 2-chloro-l,l,l-trifluoroethane (HCFC-133b) and 2,2-dichIoro-l,l,l-trifluoroethane (HCFC-123b) are industrially produced CFC alternatives, the original academic oxidative reaction to produce them is now of technical importance 7 a thermal oxidation method for 2.2-dichloro-l,1,l-trifluoroethane that is attractive from an industrial point of view has been developed7 and high yields of trifluoroacetic acid were obtained in a continuous process in addition, minor products were characterized. The acid is formed by continuous hydrolysis of the reaction mixture.7... 

Much work has been done to develop catalyst systems that optimize yield and reduce side reactions. The reaction has an induction period, which depends on the temperature and the amount of catalyst.8 An early patent from Bayer claims that a nearly quantitative yield can be achieved in the conversion of l,2-dibromo-1-chloro-l.2.2-trifluoroethane(5) into 1,1-di-bromo-l-chloro-2,2.2-trifluoroethane (6) when aluminum tribromide is used in 2-broino-2-chloro-1,1,1-trifluoroethane (4) as solvent.12 A Japanese patent26 describes the activation of aluminum trichloride or alumina by pretreatinent with l,L2-trichloro-l,2,2-trifluoroethane (1) (see discussion of compound 19, vide infra). A later patent claims that aluminum trichloride and tribromide can also be activated by complexing with 1,1-dichloro- (CF3CFC12) and 1,1-dibromo-1,2,2,2-tetrafluoroethane (CF3CFBr2), respectively 2 an example of the latter is shown in the formation of bromofluoroalkane 10. 

As discussed (vide supra) disproportionation and isomerization are often competitive reactions. The reaction rates of both types depend on the temperature and the catalyst used for the reaction. Chromium(III) oxide on support, or without, favors the disproportionation of 1,1,2-trichloro-1.2,2-trifluoroethane to give l,l-dichloro-l,2.2,2-tetrafluoroethane and 1,1,1.2-tetra-chloro-2,2-difluoroethane whereas with aluminum trifluoridc the isomerization is favored.24 The higher the chlorine content of the molecules the greater is their reactivity. 

Magnesium-mediated elimination of bromine monofluoride has been reported in the reaction of 2-bromo-2-chloro-l,l,l-trifluoroethane with ketones, e.g. reaction of 5 with octan-2-one. 

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