Difluoroethane, reaction

Reactions with Organic Compounds. Tetrafluoroethylene and OF2 react spontaneously to form C2F and COF2. Ethylene and OF2 may react explosively, but under controlled conditions monofluoroethane and 1,2-difluoroethane can be recovered (33). Benzene is oxidized to quinone and hydroquinone by OF2. Methanol and ethanol are oxidized at room temperature (4). Organic amines are extensively degraded by OF2 at room temperature, but primary aHphatic amines in a fluorocarbon solvent at —42°C are smoothly oxidized to the corresponding nitroso compounds (34). 

Another use of hydrogen fluoride, although not in halogen exchange, is the reaction with ethylenes or acetylenes to form the addition products, 1,1-difluoroethane [75-37-6] and vinyl fluoride [75-02-5]-. 

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). 

Vlayl fluoride [75-02-5] (VF) (fluoroethene) is a colorless gas at ambient conditions. It was first prepared by reaction of l,l-difluoro-2-bromoethane [359-07-9] with ziac (1). Most approaches to vinyl fluoride synthesis have employed reactions of acetylene [74-86-2] with hydrogen fluoride (HF) either directly (2—5) or utilizing catalysts (3,6—10). Other routes have iavolved ethylene [74-85-1] and HF (11), pyrolysis of 1,1-difluoroethane [624-72-6] (12,13) and fluorochloroethanes (14—18), reaction of 1,1-difluoroethane with acetylene (19,20), and halogen exchange of vinyl chloride [75-01-4] with HF (21—23). Physical properties of vinyl fluoride are given ia Table 1. 

Hydrogen haHde addition to vinyl chloride in general yields the 1,1-adduct (50—52). The reactions of HCl and hydrogen iodide [10034-85-2], HI, with vinyl chloride proceed by an ionic mechanism, while the addition of hydrogen bromide [10035-10-6], HBr, involves a chain reaction in which a bromine atom [10097-32-2] is the chain carrier (52). In the absence of a transition-metal catalyst or antioxidants, HBr forms the 1,2-adduct with vinyl chloride (52). HF reacts with vinyl chloride in the presence of stannic chloride [7646-78-8], SnCl, to form 1,1-difluoroethane [75-37-6] (53). 

Table 2). Either vinyl fluoride or 1,1-difluoroethane can be obtained ai the major product from liquid- or vapor-phase reactions. 

Phenylacetylene gives 1-phenyI-l, l-difluoroethane on reaction with a large excess of hydrogen fluoride in ether at 0 C or, in better yield, in the gas phase over a mercuric oxide catalyst [/]. Allene affords 2,2-difluoropropane [/]... 

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%). 

Fluorination of propene by xenon difluoride leads to formation of l,2-difluoropropanc(12%), 1,1-difluoropropane (46 %), 2-fluoropropane (24 %) and 1,1-difluoroethane (9 %). The complex composition of the mixture is explained by the radical character of the reaction. 

Sulfur tetrafluoride undergoes addition across the carbonyl groups of glyoxal to form 1,2-difluoroethane-l,2-diol orthosulfite 13 the reaction occurs at room temperature in the presence of a hydrogen fluoride scavanger, such as sodium fluoride.75... 

Bromo-l-chloro-l,l-difluoroethane (3) is prepared from l,2-dibromo-l,l-dichloroethane (1) in good yield when the fluorination reaction with antimony(III) fluoride/antimony(V) chloride is conducted in two steps. 

Hydrogen fluoride can also be added to acetylene with aluminum trifluoride catalysis to yield vinyl fluoride (14) and 1,1-difluoroethane (15).41 See Table 3 for reactions and byproducts under similar conditions. 

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... 

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. 

The reaction of 1-chloro-l-fluoroethane over copper(II) chloride or alumina at 180°C yields 1,1-difluoroethane and 1,1-dichloroethane.32 The conversion is 70% and the yields of both compounds are 40 and 38 %, respectively. This indicates that only minimal hydrogen chloride formation may occur during this disproportionation. 

The order of stability in highly fluorinated compounds is CF3 > CF2 > CF. The C-F bond of 1,2-difluoroalkanes is very unstable and hydrogen fluoride is readily eliminated in the presence of a base. Thus. 1.2-difluoroethane released hydrogen fluoride even at room temperature. The introduction of more than one fluorine into alkanes results in a stabilization of the C-F bond. Therefore, gcm-difluoroalkanes -CF2CH2- are inert towards weaker bases such as sodium hydroxide or sodium methoxide, and their dehydrofluorination requires stronger bases (r-BuOK or LDA) combined with a prolonged reaction time. 1,1-Difluoroethane is completely stable towards bases.15... 

While the direct reaction of HF and acetylene requires high pressure, proceeds in only low conversion and gives mixtures, a number of catalyst systems have been reported to give improved results.23 Addition of boron trifluoride, however, favors the formation of 1,1-difluoroethane. Similar results are reported for... 

Dibromofltjoroethane and l-Bromo-2,2-difluoroethane. By a procedure analogous to that just described, 1,2,2-tribrojnoethane was converted to the mono- and di-fluoro derivatives. The reaction temperature had to be lower for good results. At 0°, the yield of fnixed products was 50% at — 20°, 60-65%. At higher temperatures the yield was only 30%. The boiling points are 121° and 57°, respectively. 

Difiuoropropane (CH3CF2CH3).60 The vapor of 1 mole of propyne (b.p. —23.3°) is introduced into 4 moles of liquefied hydrogen fluoride in a metal container held at —23° by means of a carbon tetrachloride bath to hich enough solid carbon dioxide has been added to keep it mushy. Care is exercised to prevent the escape of any vapors. The reaction occurs at once. After completion of the addition, the reaction mixture is allowed to warm, and the vapors are passed through water and then condensed in a receiver cooled with solid carbon dioxide. The distillation of the condensate yields 54 g. (64%) of 2,2-difluoroethane, CH3CF2CH3, b.p. 0°. Lower reaction temperatures retard the addition, whereas higher temperatures favor polymerization. 

The catalytic hydrofluorination of acetylene has been reported in detail.24,5 34-541 The reaction products are polymerizable fluoroethene (1) and 1,1-difluoroethane, which can be used as a coolant or low boiling solvent, e.g. as an aerosol propellant. 

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