The pure electrophilic nature and unique reactivity characteristics and perfluoro-n-alkyl radicals have made the quantitative determination of their reactivity a matter of fundamental significance. Initial insight into the behavior of such radicals was obtained in our recently reported study which resulted in determination of absolute rate constants for their addition to a broad spectrum of alkenes.1.2 In these LFP experiments it was found that perfluorinated radicals were much more reactive than their hydrocarbon counterparts in additions to normal, electronrich alkenes, such as 1-hexene (40 000 times as reactive).In this paper we report the use of this LFP data in conjunction with a series of bimolecular competition experiments to determine approximate absolute rate constants for some hydrogen atom transfer reactions of the perfluoro-n-heptyl radical with substituted silanes and thiophenol, and then we demonstrate how these data can be used to determine the rates of cyclization of some fluorinated alkenyl radicals, which as such comprise the first reported fluorinated 'clock" reactions.Recently we reported that the rate of hydrogen atom transfer to n-C7FIS* by tributyltin hydride was -75 times that to n-alkyl radicals at 30 O C . 2 In the present work even more greatly enhanced rates of hydrogen atom transfer to Rf* (vs R') by three common silane reducing agents are observed. For example, in contrast to its relatively low reactivity with hydrocarbon radicals, where it has been found to be virtually useless as an effective chain-sustaining hydrogen atom transfer agent,3 triethylsilane was observed to reduce perfluoroalkyl bromides and iodides efficiently under photochemical initiation, transferring hydrogen atoms to the intermediate perfluoro-n-alkyl radicals at a rate which should make Et3SiH a very useful competitive reducing agent for studying chain processes which involve fluorinated radicals. As seen in Table 1, Et3SiH was >850 times more reactive with Rf' than with R' at 30 OC. In a similar manner, the even more reactive reducing agents (TMS)ZSiHMe and (TMS),SiH were shown to transfer hydrogen atoms -440 and -110 times Contribution No. 6795. (1) Avila, D. V.; Ingold, K. U.; Lusztyk, J.; Dolbier, W. R., Jr.; Pan, H.-Q.( 2 ) Avila, D. V.; Ingold, K. U.; Lusztyk, J.; Dolbier, W. R., Jr.; Pan, H.-Q.; (3) Lusztyk, J.; Maillard, B.; Ingold, K. U.Table 1. Rate Constants for Hydrogen Atom Abstractions a t 30 OC rate of reduction (k~/(106 M-I s-')) (TMS)2-(TMS)y n-Bus-Radical PhSH EtoSiH SiMeH SiH SnH R-CH2'" 150 0.OOO 85 0.037 0.46 2.76 n-C7F15' 0.28 (0.03) 0.75 (0.07) 16.3 (1.5) 51 (5) 203 (14) Reference 7. Reference 2.more rapidly, respectively, to perfluoro-n-alkyl than to the analogous hydrocarbon radicals.& The observed enhanced rates of Rf* with the silanes and n-Bu,-SnH are consistent with the greater exothermicity of such reductions ( R r H BDE = 107 kcal/molvs 98 kcal/mol for R-H).* However, this certainly cannot be the whole story since it was found that PhS-H, a very efficient H atom donor to hydrocarbo...

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Teflon® AF, a family of copolymers of perfluoro‐2,2‐dimethyldioxole with tetrafluoroethylene, and Cytop®, a ring‐cyclized homopolymer of CF2=CFO(CF2)2CF=CF2 are the first commercial amorphous perfluoroplastics which combine high optical clarity and solubility with outstanding chemical, thermal and electrical properties. The processes for making these materials are described and recent structure‐property studies that reveal dramatic substituent effects on polymer Tg and related properties are reviewed. The results of some initial fundamental kinetic studies on fluorinated free‐radical cyclizations that relate to efficient cyclopolymerization of fluorinated dienes and the design of new ring‐containing fluoroplastics are discussed.

In 1994, Aoyama reported in a Daikin patent the facile synthesis of 1,1,1,4,4,4-hexafluoro-2-butene (HFC-356mff) from the inexpensive hydrochlorofluorocarbon 1,1,1-trifluoro-2,2-dichloroethane (HCFC-123) by heating it at 60 °C with metallic copper in diethylamine. 1 We reproduced that result, but found a small but significant impurity, CF 3 CH 2 Cl, which proved very difficult to separate. In an attempt to further minimize this impurity, the reactions of CF 3 CHCl 2 with a number of different secondary amines were examined (Table 1), and to our surprise we found that, among those tried, only diethylamine gave a respectable yield of HFC-356mff. Instead, we observed another major product being formed in the case of many of the alternative secondary amines, that being the respective 1,1-bis(dialkylamino)-2,2,2trifluoroethanes 1a-e. [2][3][4] In view of considerable precedent, it seemed probable that compounds such as 1a-e could be used as precursors for the potentially very useful fluorinated "enolate" building block 2. [5][6][7][8][9][10][11] Indeed, treatment of 1a (in ether) with 1.1 equiv of n-BuLi (2.5 M in hexane) at -78 °C, followed by warming to room temperature where it was allowed to stir for 10 h, led to its >90% conversion to 2, which could be used readily for subsequent reactions in situ at temperatures from -78 °C to rt. 12 Reagents such as 2 have attracted much interest because of their ambiphilic character, which allows them to exhibit either nucleophilic or electrophilic character in their reactions. 5,8,10,11,[14][15][16][17][18][19][20][21][22] For example, enol ethers 3 and 4 condense readily with aldehydes or ketones, 10,21 and it has been observed that the related difluoroketene thioacetal, 5, undergoes nucleophilic attack by either alkyllithiums or Grignard reagents. 5 Nakai and his coworkers have, moreover, observed that perfluoroenolates, such as 6, undergo both electrophilic and nucleophilic attack. 11,16 Our preliminary studies of the reactivity of 2 have confirmed that it can also exhibit both nucleophilic

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