Perfluoroolefins

The heat of formation of C3F6 is —263.4 kcal/mole as computed from the relationship 

C-CaFe -233.4 Appearance potentials from C3F8 and c-C3F8 Lifshitz and Long108 

C2F3 -55.9 Resonance capture processes Lifshitz and Grajower107a 

---

Table 1. Oxidation of Perfluoroolefins to Perfluoroepoxides by Sodium Hypoctaioride...

Unlike perfluoroaliphatic organometallies, perfluoroolefinic and perfluoro-acetylemc Grignard reagents have a greater thermal stability and can be prepared and used as intermediates at temperatures around 0 C [40]... 

Polyfluoroparafins, fluorocarbons, and other perfluoro denvatives show remarkable heat stability They are usually stable at temperatures below 300 C Thermal decomposition at 500-800 °C, however, causes all possible splits in the molecules and produces complex mixtures that are difficult to separate For preparative purposes, only pyrolyses that do not yield complicated mixtures of products are of interest [7] The pyrolytic reacpons of polyfluoro and perfluoro derivatives, when carried out at 500-11 Ofl °C, represent the most useful route to preparative generation of perfluoroolefins on the laboratory scale [7]... 

Perfluoroolefins isomerize photochemically to yield less substituted olefins [272] Photolysis of polyfluorotriarylmtrones leads to polyfluorotriaryloxaziridines [173] (equation 43)... 

Ruorocarbon elastomers are convemently divided mto three groups (1) the most widely used group of copolymers of VDF and one or two perfluoroolefins, (2) a less widely used group based on TFE and simple hydrocarbon olefins, and (3) a much smaller group compnsmg copolymers of TFE and jierfluoroolefms [/, 7, 30]... 

Dehydrofluorination by primary and secondary aliphatic amines occurs at room temperature and is the basis of diamine cross linkmg, which occurs by dehydrofluonnation and subsequent nucleophihc substitution of the double bond The locus of dehydrofluonnation is a VDF unit flanked by two perfluoroolefin units This selectively base-sensitive methylene group also undergoes elimination as the first step in phase-transfer-catalyzed cross-hnking with quaternary ammo mum or phosphomum salts, bisphenols, and morganic oxides and hydroxides as HF acceptors [31, 32]... 

It has been reported that perfluoroisobutylene and perfluorocyclobutene undergo 1,2 cycloaddition with l-(N-morpholino)isobutylene in ether at room temperature to give the corresponding perfluorocyclobutane derivatives ]20a). Enamines of cyclic ketones produce only simple alkylation products when treated with these perfluoroolefins. 

Lithium chlorodifluoroacetate in preparation of perfluoroolefins from perfluoroalkyl ketones, 48, 119... 

Addition of sulfur chlorides to perfluoroolefins furnishes a series of interesting sulfenyl chlorides 100) ... 

In contrast to a-elimination, jS-ehmination processes are very common in reactions involving fluoroalkyl compounds and perfluoroolefins (Figure 1.11). 

Rate-Constant Ratios for Reactions Involving Excited Epoxides from Oxygen-Atom-Perfluoroolefin Reactions Ratio Value Units T, °C Reference... 

The reaction of oxygen atoms with C4Fe-2 has been examined at room temperature by Johnston and Heicklen.93 Contrary to the reaction with the smaller perfluoroolefins, the important reaction is not cleavage of the double bond. The principal product of the reaction for C4F6-2 pressures between 10 and 100 torr was z-C3F7CFO. Other products were CF3CFO,... 

Rate-Constant Ratios for Reactions of Electronically Excited Perfluoroolefins Produced by Hg Sensitization... 

Volman173 has found that d>(03) is only 0.03 even with one atm of 02. Consequently, reaction (4-54) is unimportant compared with reaction (4-53). The excited oxygen molecule can also react with perfluoroolefins to ultimately yield oxidation products. The evidence suggests that the initial step is energy transfer83-86... 

Some Rate Constants for Reactions of 02 with Perfluoroolefins Relative to 02 at 25°Ca... 

The reaction of 03 with C2F4, C3F6, and C4F8-2 was studied at room temperature by Heicklen.72 He introduced 03 into the perfluoroolefin in a cell situated in the sample beam of an infrared spectrometer. The products included 02 and CFzO in all cases. With C3Fe and C4Fe-2, CF3CFO was also formed but it was always less important than CFaO. 

Rate Constants in the 03-Perfluoroolefin System at Room Temperature a... 

With perfluoroolefins atomic oxygen does not give normal adducts, but instead causes cleavage of the double bond.11 With terminal olefins triplet difluoromethylene apparently is a major product, and its addition to excess olefin to form perfiuorocyclopropanes is quenched by molecular oxygen. 

Synthetic methods have limited the preparation of saturated perfluoropolyethers. The most successful perfluoropolyether synthetic chemistry has been DuPont s anionic polymerization of perfluoroepoxides, particularly hexafluoro-propylene oxide and tetrafluoroethylene oxide (39). Their synthetic procedure is a three-step scheme for saturated perfluoropolyether production involving oxidation of perfluoroolefins to perfluoroepoxides, anionic polymerization to acyl fluoride terminated perfluoropolyethers, and conversion of acyl fluoride end groups to unreactive end groups by decarboxylation reactions or chaincoupling photolytic decarboxylate reactions. 

Complexes of cyclic perfluoroolefins are also quite common. For example, the iron and platinum complexes of perfluorocyclobutene, 20 (62) and 21 (56), have been prepared. Recently the chemistry of the smallest cyclic perfluoro-olefin, perfluorocyclopropene, has been explored, and initial results indicate... 

II. Reactions of Binucleophilic Reagents with Terminal Perfluoroolefins. 137... 

---