Reaction with hexafluoropropylene oxide

Fluorinated ether-containing dicarboxyhc acids have been prepared by direct fluorination of the corresponding hydrocarbon (17), photooxidation of tetrafluoroethylene, or by fluoride ion-cataly2ed reaction of a diacid fluoride such as oxalyl or tetrafluorosuccinyl fluorides with hexafluoropropylene oxide (46,47). Equation 8 shows the reaction of oxalyl fluoride with HEPO. A difunctional ether-containing acid fluoride derived from HEPO contains regular repeat units of perfluoroisopropoxy group and is terminated by two alpha-branched carboxylates. 

Hexafluoropropylene Oxide HFPO is the most important of the perfluoroepoxides and has been synthesized by almost all of the methods noted. Many attempts have been made to polymerize HFPO (6,8). The most successful has been the reaction of HFPO with fluoride ion at low temperature to give a series of oligomeric acid fluorides which have been end capped to yield stable fluids (eq. 11, where X = H,F). 

Preparation. The preparation of tetrafluoroethylene has been described previously. Perfluorovinyl ethers (4—7) are prepared by the following steps. Hexafluoropropylene [116-15-4] (HEP) is oxidized to an epoxide HEPO [428-59-1] (5) which, on reaction with perfluorinated acyl fluorides, gives an alkoxyacyl fluoride. 

Hexafluoropropylene oxide (HFPO), which decomposes reversibly to di-fluorocarbene and trifluoroacetyl fluonde with a half-life of about 6 h at 165 °C [30], is a versatile reagent. Its pyrolysis with olefins is normally carried out at 180-2(X) °C, and yields are usually good with either electron-nch or electron-poor olefins [31, 32, 33, 34, 35, 36, 37] (Table 2). The high reaction temperatures allow the eyclopropanation of very electron poor double bonds [58] (equation 10) but can result in rearranged products [39, 40, 41] (equations 11-13)... 

Prepared from DuPont s Krytox FSL functional oil, consisting of oligomers of hexafluoropropylene oxide capped with carboxylic acid group, via reaction with thienyl chloride, followed by reaction with 2,3-dithio-1-propanol. 

Surface modifications of polymers is brought about by the introduction of alcohol functionality, e.g., poly(tetrafluoroethylene-co-hexafluoropropylene) on reduction with sodium naphthalide in THF results in an unsaturated modified surface layer, the thickness of which is controlled with reaction time and temperature. The air sensitive surface contains alcohols, ketones, aliphatic C-H bonds in addition to C=C and C C. The more alcoholic groups are introduced by hydroboration-oxidation, but the esterification leads to the formation of ester in lower yield. This reveals that the reactivity of OH group is similar to hindered alcohols. The reactivity of the surface can be enhanced by chain extension of secondary surface alcohols with ethylene oxide to form a surface containing primary alcohols groups separated from the polymer backbone by C-2 spacer. On the other hand, primary alcohols are directly introduced to the surface by reaction of the reduced layer with 9-BBN, followed by carbonylation and reduction [5]. 

A cyclic lactone is formed by the reaction of 1,4 diiodo-perfluorobutane with oleum (see Fig. 47). The addition of methanol to the lactone gives selectively 3-methoxycar-bonyl perfluoro-propionyl fluoride, to which hexafluoropropylene oxide is added. After copolymerization with tetrafluoro ethylene, the acid fluoride group is converted to a perfluorovinyl group by pyrolysis. 

The application of nitrogen oxide enables to prepare spin-labelled macromolecules in chemically inert and insoluble pol5miers, for example, in pol q)erfluoroalkanes. As was shown in the work [16], the radiolysis of oriented films of polytetrafluoroethylene (PTFE) and copol5mier of tetra-fluoroethylene with hexafluoropropylene initiates reactions with formation of iminoxyl macroradical according to the following scheme ... 

It does not homopolymerize easily and hence can be stored as a liquid. It undergoes many addition reactions typical of an olefin. Reactions inclnde preparation of linear dimers and trimers and cyclic dimers (21,22) decomposition at 600°C with subsequent formation of octafluoro-2-butene and octafluoroisobutylene (23) oxidation with formation of an epoxide (24), an intermediate for a number of perflu-oroalkyl perfluorovinyl ethers (25,26) and homopolymerization to low molecular weight liquids (27,28) and high molecular weight solids (29,30). Hexafluoropropylene reacts with hydrogen (31), alcohols (32), ammonia (33), and the halogens and their acids, except I2 and HI (31,34-36). It is used as a comonomer to produce elastomers and other copolymers (37-41). The toxicological properties are discussed in Reference 42. 

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