Tetrafluoroethylene synthesis

None of fluoropolymers or their decomposition products poses any threats to the ozone layer. None are subject to any restrictive regulations under the Montreal Protocol and the US Clean Air Act. Reacting HF with chloroform produces the main fluori-nated ingredient of tetrafluoroethylene synthesis CHCIF2. It has a small ozone depleting potential but is excluded from the Montreal Protocol regulation... 

Although the CFCs and HCFCs are not as stable as the PFCs, they still can be rather stable compounds (3,11)- Dichlorodifluoromethane, CCI2F2, is stable at 500°C in quartz CCl F and CHCIF2 begin to decompose at 450 and 290°C, respectively (7). The pyrolysis of CHCIF2 at 650—700°C in metal tubes is the basis of a commercial synthesis of tetrafluoroethylene ... 

The synthesis of 2-chloro-2,3,3-trifluorocyclobutyl acetate illustrates a general method of preparing cyclobutanes by heating chlorotrifluoroethylene, tetrafluoroethylene, and other highly fluorinated ethylenes with alkenes. The reaction has recently been reviewed.11 Chlorotrifluoroethylene has been shown to form cyclobutanes in this way with acrylonitrile,6 vinylidene chloride,3 phenylacetylene,7 and methyl propiolate.3 A far greater number of cyclobutanes have been prepared from tetrafluoroethylene and alkenes 4,11 when tetrafluoroethylene is used, care must be exercised because of the danger of explosion. The fluorinated cyclobutanes can be converted to a variety of cyclobutanes, cyclobutenes, and butadienes. 

The first reactions of fluorinated olefins in C02 reported by DeSimone et al. involved the free-radical telomerization of 1,1 -difluoroethylene29 and tetrafluor-oethylene.30 This work demonstrated the feasibility of carrying out free-radical reactions of highly electrophilic species in solvents other than expensive fluorocarbons and environmentally detrimental chlorofluorocarbons. The work has since been more broadly applied to the synthesis of tetrafluoroethylene-based, nonaqueous grades of fluoropolymers,31,32 such as poly(tetrafluoroethylene-co-peduoropropylvinyl ether) (Scheme 2). These reactions were typically carried out at between 20 and 40% solids in C02 at initial pressures of between 100 and 150 bars, and 30-35°C (Table 10.1). 

Tetrafluoroethylene-(TFE)-perfluoropropyl vinyl ether copolymers, 7 641 Tetrafluoroethylene-perfluorovinyl ether, 48 329-339. See also Teflon PFA copolymerization of, 48 330—331 Tetrafluoroethylene-perfluorodioxole copolymers, 48 339—342. See also Teflon AF copolymers applications of, 48 342 economic aspects of, 48 341—342 health and safety factors related to, 48 342 monomer preparation, 48 339 synthesis of, 48 339-340 Tetrafluoroethylene (TFE) copolymerization with... 

As discussed above, the most commonly known and studied PEMs are based on nonaromatic perfluori-nated hydrocarbons such as Nation, Aciplex, Flemion, and what are termed the Dow membranes. However, their chemical synthesis is challenging due to the safety concerns of tetrafluoroethylene and the cost/ availability of the perfluoroether comonomers. These issues have relegated detailed synthetic research on polyperfluorosulfonic acid materials to the industrial sector or to a few specialized academic labs. 

Fluoroatcohols. A group of fluorine contg alcohols are available commercially having the general formula H(CFa.GF2)nCH20H, in which n = 1 to 5 They include ales contg C3, C, C7, C9 Ctl, Density of Liquids 1.48-1.66, nD 1.318-1.320 (lowest of all known org compds). Derived by. free radical telomerization of tetrafluoroethylene with methanol. Used as solvents and in org synthesis... 

Romack, T. J. DeSimone, J. M. Synthesis of Tetrafluoroethylene-Based, Non-aqueous Fluoropolymers in Supercritical Carbon Dioxide. Macromolecules 1995, 28, 8429-8431. 

The compilation of such data constituted a firm basis that was used to study a specific and more complicated system the elucidation of the electronic structure of a copolymer of ethylene (48%) and tetrafluoroethylene (52%) whose synthesis was conducted in order to maximize the alternating sequences. The valence band spectrum of such a compound (Figure 8) was found very similar to the one measured e.g. for poly(vinylidene fluoride). But, by looking to the fine details of the spectrum, by simulating the valence band of a block copolymer (by addition of PE and PTFE spectra), and by comparison with model calculations, it was possible to show that the C-C band width and the distance F2s-top of the C-C band were characteristic of an ethylene-tetrafluoro-ethylene copolymer with dominant alternant structure (28). 

When heated above 170"C hexafluoropropylene oxide (5) is a source of difluorocarbene thus, heating 5 in the presence of an alkene allows the synthesis of fluorinated cyclopropanes under neutral conditions.14 16 The less readily available tetrafluoroethylene oxide (6) is also a precursor of difluorocarbene.17... 

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