Ethers, vinyl with sulfonic acids

Nafion is a copolymer of poly(tetrafluoroethylene) and polysulfonyl fluoride vinyl ether. It has fixed anions, which are sulfonic acid sites, and consequently, by electroneutrality, the concentration of positive ions is fixed. Furthermore, the transference number of protons in this system is 1, which greatly simplifies the governing transport equations, as seen below. There can be different forms of Nafion in terms of the positive counterion (e.g., proton, sodium, etc.). Most models deal only with the proton or acid form of Nafion, which is the most common form used in polymer-electrolyte fuel cells due to its high proton conductivity. 

Cycloaddition of nitrones (e.g. 166, equation 107) to alkoxyaUtenes proceeds in high yield with complete diastereoselectivity, giving 1,2-isoxazolidines of type 167. Similar reactions have been reported for vinyl ethers , vinyl acetate , enamines , vinyl imidazoles , enamides, vinyl sulfones and vinyl sulfides . Since the resultant 1,2-oxazolidines of type 167 and its analogs can be hydrolyzed under acidic conditions, this reaction may also be considered as an approach to O-unsubstituted N-alkylhydroxylamines . 

Nation ionomers are produced by copolymerization of a perfluorinated vinyl ether comonomer with tetrafluoroethylene resulting in the chemical structure shown in Figure 8.25 [162,166], This polymer and other related polymers consist of perfluorinated, hydrophobic, backbones that give chemical stability to the material. The material also contains sulfonated, hydrophilic, side groups that make hydration possible in the acidic regions, and also allow the transport of protons at low temperatures, since the higher limit of temperature is determined by the humidification of the membrane, since water is a sine qua non for conduction [166], The material exhibits a proton conductivity of 0.1 S/cm at 80°C [162], The membrane performance is then based on the hydrophilic character of the sulfonic acid groups, which allow proton transport when hydrated while the hydrophobic... 

Attempted Synthesis of Specific Hexenyl Acetate Isomers. From Hexanal. Hexanal (5 ml. of 40% technical material) and 25 ml. 2-propenyl acetate were mixed, and 750 mg. p-toluene sulfonic acid was added. This solution was heated at reflux for 12 hours. The solution was then poured into 100 ml. water and extracted with two 50-ml. portions of ether. The combined ether extracts were washed with water, dilute aqueous sodium bicarbonate, and water and dried over sodium sulfate. After evaporating the ether, a gas chromatogram showed two major components present in a 3 2 ratio (probably the trans- and cis-hex-l-en-l-ol acetates, respectively). These components had identical retention times in the gas chromatograms to two of the major components present in the hexene-1 vinylation reactions. 

Sulfones (55) are generally prepared by the oxidation of the appropriate sulfides (2) (Scheme 26).7 The oxidation is generally performed by treatment with peroxycarboxylic acids, but other oxidants may be used (see Chapter 10, p. 195). Diarylsulfones are often obtained by the Friedel-Crafts reaction, and special methods are available for the synthesis of substituted sulfones such as vinyl, hydroxy and halosulfones (see Chapter 10, p. 197). Sulfonyl ethers (56) can be prepared by reaction of a suitable chloroether (57) with the appropriate - sodium sulfinate (58) (Scheme 27). 

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. 

ETHER, VINYL ETHYL (109-92-2) C4HgO Highly flammable, polymerizable liquid. Forms explosive mixture with air [explosion limits in air (vol %) 1.7 to 28 flash point <-50°F/<-46°C autoignition tenqj 395°F/202°C Fire Rating 4]. Forms unstable peroxides on contact with air. Reacts violently with oxidizers, ammonium persulfate, bromine dioxide, methane sulfonic acid (may cause polymerization), nitric acid, perchlorates, permanganates, peroxides and hydroperoxides, sulfuric acid. Incompatible with acids, ammonia, aliphatic amines, alkanolamines. On small fires, use dry chemical powder (such as Purple-K-Powder), alcohol-resistant foam, or COj extinguishers. 

D.J. Connolly and W.F. Gresham, Fluorocarbon vinyl ether polymers. USP 3,282,875, 1966 P.R. Resnick, Preparation of sulfonic acid containing vinyl ethers, USP 3,560,568 K. Kimoto, H. Miyauchi, J. Ohmura, M. Ebisawa and H. Hane, Novel fluorinated copolymers with tridihydro fluorosulfonyl fluoride pendant groups and preparation thereof. USP 4,329,435. 

In the previous section it was suggested that the parent polymer structure considerably influence the physical properties of the derived polysulfonates, imparting to them some of the mechanical and thermal properties of the precursors. This trend is particularly evident in the case of the perfluorinated hydrocarbon polymers. Polymers of this kind, such as e.g., poly(tetrafluoroethylene) (PTFE) are exceptional in their inertness to offensive environment, solvent resistance and high-temperature stability. These considerations led in the sixties to the development of unique sulfonic-acid derivatives of fluorocarbon copolymers by the DuPont Company. While several compositions were disclosed in the patent literature51, the preferred composition, which is the basis for the commercial Nafion ion-exchange membrane, is a copolymer of tetrafluoroethylene with a perfluorinated vinyl ether/sulfonyl fluoride52 ... 

Addition to vinyl ethers and vinyl esters is regioselective, leading to the corresponding j8-alkyloxy/acyloxy sulfone. Addition to alkynes gives vinyl sulfones via a radical pathway. These reactions can be carried out in the presence of peroxide initiators, with Lewis acids such as copper(II) bromide (eq 4), or thermally (eq 5). - ... 

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