Vinyl fluoride preparation

Xenon difluoride (XeF ) is the electrophilic fluorinating reagent whose reactions with vinyltin compounds have been studied most exhaustively. " A series of vinyl fluorides prepared according to this procedure is listed in Table 1. 

Quantitative measurement shows about 11% of the monomer units to be inverted. The principal spectrum shows splitting into mm, mr, and rr triad resonances with some pentad fine structure. The polymer is nearly atactic. Assignment of inversion "defect" resonances is made easier by reference to spectrum (b), which is that of poly (vinyl fluoride) prepared by the following route (17) ... 

The assignment was confirmed by examination of poly (vinyl fluoride) free from inverted units. This material was made by reductive dechlorination of poly(l-fluoro-l-chloroethylene) by means of tri-n-butyltin hydride the bulky chlorine atom in the monomer effectively prevents head-to-head growth. The F spectrum of poly (vinyl fluoride) prepared by this indirect route contained only the signals in the range 178-185 ppm. 

Figure 3.11 The F spectra of (A) commercial poly(vinyl fluoride) and (B) poly(vinyl fluoride) prepared without head-to-head and tail-to-tail defects. The spectra were acquired as an 8% solution in N,N-dimethylformamide-d7. The resonances marked A correspond to head-to-tail sequences while B and C represent the head-to-head and tail-to-tail defects. Reprinted with permission from...

In another vinyl fluoride preparation method, hydrofluoric acid is added to acetylenet 1 to produce 1,1-difluoroethane. Next, 1,1-difluoroethane is pyro-lyzed over an aluminum salt and a molecule of hydrofluoric acid is removed, thereby producing VF. The product is passed through soda lime in towers to remove hydrofluoric acid followed by acetylene removal in ammoniacal cupric chloride. Oxygen is separated by distillation. 

Hydrofluorocarbons are also prepared from acetylene or olefins and hydrogen fluoride (3), or from chlorocarbons and anhydrous hydrogen fluoride in the presence of various catalysts (3,15). A commercial synthesis of 1,1-difluoroethane, a CFG alternative and an intermediate to vinyl fluoride, is conducted in the vapor phase over an aluminum fluoride catalyst. 

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. 

Copolymers of VF and a wide variety of other monomers have been prepared (6,41—48). The high energy of the propagating vinyl fluoride radical strongly influences the course of these polymerizations. VF incorporates well with other monomers that do not produce stable free radicals, such as ethylene and vinyl acetate, but is sparingly incorporated with more stable radicals such as acrylonitrile [107-13-1] and vinyl chloride. An Alfrey-Price value of 0.010 0.005 and an e value of 0.8 0.2 have been determined (49). The low value of is consistent with titde resonance stability and the e value is suggestive of an electron-rich monomer. 

Vinyl fluoride (fluoroethene), is manufactured from the cataly2ed addition of hydrogen fluoride to acetylene. It is used to prepare poly(vinyl fluoride) which has found use in highly weather-resistant films (Tedlar film, Du Pont). Poly(vinyhdene fluoride) also is used in weather-resistant coatings (see Eluorine compounds, organic). The monomer can be prepared from acetylene, hydrogen fluoride, and chlorine but other nonacetylenic routes are available. 

Polymer Solvent. Sulfolane is a solvent for a variety of polymers, including polyacrylonitrile (PAN), poly(vinyhdene cyanide), poly(vinyl chloride) (PVC), poly(vinyl fluoride), and polysulfones (124—129). Sulfolane solutions of PAN, poly(vinyhdene cyanide), and PVC have been patented for fiber-spinning processes, in which the relatively low solution viscosity, good thermal stabiUty, and comparatively low solvent toxicity of sulfolane are advantageous. Powdered perfluorocarbon copolymers bearing sulfo or carboxy groups have been prepared by precipitation from sulfolane solution with toluene at temperatures below 300°C. Particle sizes of 0.5—100 p.m result. 

Poly(vinyl fluoride) was first introduced in the early 1960s, in film form, by Du Pont under the trade name Tedlar. Details of the commercial method of preparing the monomer have not been disclosed but it may be prepared by addition of hydrogen fluoride to acetylene at about 40°C. 

Convenient syntheses of vinyl fluorides are of synthetic interest, fhe conjugate base of fluoromethyl phenyl sulfone reacts with carbonyl compounds to provide P-tluoro alcohols, which are used to prepare terminal vinyl fluorides [25] (equation 23) (Table 9) This reaction offers an alternative to the Winig reaction, which may be very sensitive to reaction conditions. 

Although vinyl fluoride was prepared around 1900, it was believed to be resistant to typical vinyl polymerization. German scientists prepared vinyl fluoride through reaction of acetylene with hydrogen fluoride in the presence of catalysts in 1933. 

All of the possible ring-fluorinated isomers of 1,2,4-trioxolane are known and these can be prepared by ozonolysis of the corresponding vinyl fluorides 3-fluoro-1,2,4-trioxolane <79JOC3i8i> cis- and rani-3,5-difluoro derivatives <77JA7239> and 1,1-difluoro-1,2,4-trioxolane <83JA5047>. 

Carbonyl reagents, such as semicarbazide and phenelzine (27), are inactivators of SSAO. In a strategy that includes two inactivating structural motifs (allylamine and hydrazine), a series of allyl hydrazines including the series 28a-c as well as the fluoroallyl analogue 29 were prepared. Compounds 28a-c were potent irreversible inhibitors of SSAO, and compounds 28a,c had particularly good selectivity with respect to MAO inhibition. The presence of the vinyl fluoride in 29 had little effect on potency but did result in a loss in selectivity [82]. 

Vinyl fluorides can also be prepared starting from difluorovinyl compounds via the loss of a fluorine atom by an addition-elimination process, as illustrated in Figure 2.9." ... 

There are several methods to prepare vinyl fluoride (VF) monomer. One of the methods described in patent literature is a two-step method.60 The first step is the reaction of hydrogen fluoride with acetylene in the presence of a suitable catalyst to yield ethylidene fluoride, which is subsequently pyrolyzed ... 

The use of fluorine in molecules of pharmacological interest is well known and there has been widespread research into methodologies for the introduction of this atom. Within the discovery synthesis of maraviroc, the initial preparation required the use of diethyl amino sulfur trifluoride (DAST), which is commercially available but does require careful handling due its well known thermal instability. Initial use of DAST for the fluorination of the ketone 19 gave an inseparable 1 1 mixture of the required difluoro compound 20 and the vinyl fluoride 21. The formation of vinyl fluoride co-products from the treatment of ketones with DAST is known in the literature and is difficult to control. 

Polymerization of Styrene Solutions of Volatile Hydrocarbons. Addition of Hydrocarbon before Polymerization. Bulk Polymerization. Expandable polystyrene was prepared inadvertently in 1945 in an attempt to bulk copolymerize 10% isobutylene with styrene. The product formed a low density foam when heated (96). An early method (1950) for rendering polystyrene expandable by petroleum ether was to dissolve 6 parts of petroleum ether in a 40% solution of polystyrene in benzoyl peroxide-catalyzed styrene and to hold the mass for 28 days at 32 °C. (124). In a recent version of this process, the monomer (chlorostyrene) and blowing agent (trichlorofluoromethane) in a poly (vinyl fluoride) bag were irradiated with y-rays (105). 

One of the most convenient synthetic routes for the preparation of vinyl fluorides 2 is by treatment of the corresponding vinyltin compounds 1 with electrophilic fluorinating reagents. This procedure is also used for the preparation of aryl fluorides, since it is well-established that fluorination with electrophilic reagents is facilitated by ipso substitution of a suitable, usually weakly bonded, metal function. In the case of aryl fluorides, the reaction is also carried out using elemental fluorine as the fluorinating agent. ... 

Fluoro-2, 3 -unsaturated L-nucleosides have been prepared by condensing the reagent with a fluorophosphonate ester. The resulting vinyl fluoride was then transformed into the 2-fluorobute-nolide, from which a variety of L-nucleosides could be prepared (eq 6). ... 

Vinyl fluoride imdergoes free-radical polymerization.The first polymerization involved heating a saturated solution of VF in toluene at 67° C under 600 MPa for 16 hr. A wide variety of initiators and polymerization conditions have been explored. Examples of bulk and solution polymerizations exist however, aqueous suspension or emulsion method is generally preferred. Copolymers of VF and a wide variety of other monomers have been prepared. More recently, interpolymers of VF have been reported with tetrafluoroethylene and other highly fluorinated monomers, such as hexafluoropropylene, perfluorobuty-lethylene, and perfluoroethylvinylether. 

Tsai, H.-J., Lin, K.-W., Ting, T.-H., and Burton. D.J., A general and efficient route for the preparation of phenyl-substituted vinyl fluorides, Helv. Chim. Acta, 82, 2231. 1999. 

These compounds are synthesized by the copolymerization of tetrafluoroethylene and alkyl vinyl ether with sulfonyl acid fluoride. Preparation of sulfonyl acid fluoride takes place by pyrolysis of the respective oxide to give the olenfinated structure [7], The thermoplastic produced is extruded into a film. The sulfonyl fluoride (-S02F) group present in the thermoplastic is converted to sulfonate (-S()3 Na+) with NaOH. This is called the neutral form of Nafion, and it is converted to the acid for and cast into a thin film by heating in alcohol at 250°C. At around 650/m2, the Nafion membranes are rather expensive when compared to hydrocarbon membranes, which are also used. 

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