Tetrafluoroethyl Group

For example, the 1,2,2 trifluoroethyl group has found use in the fungicide tetraconezole (6-1), whereas the 1,1,2,2-tetrafluoroethyl group is encountered in the benzoylphenylurea insecticide hexaflumuron (6-2), which is used to control locust and grasshoppers in Sahalian grasslands (Fig. 6.1). 

The 1,1,2,2-tetrafluoroethyl group, usually appearing as either the ether or the sulfide, is quite commonly encountered, probably because of its... 

The commercial anesthetic desflurane is a prime example of a bioactive compound containing a 1,2,2,2-tetrafluoroethyl group. In general, this group is not commonly encountered, and when it is seen, it is usually as an ether or a sulfide (Scheme 6.6). 

What are available of proton and carbon data for compounds containing the 1,2,2,2-tetrafluoroethyl group are given in Scheme 6.7. Note that the vicinal F—H coupling constants for the sulfides are much greater than those of the analogous ethers. 

The 1,1,2,2-tetrafluoroethyl group, usually appearing as either the ether or the sulfide, is quite commonly encountered, probably because of its relative ease of synthesis from nucleophilic additions to tetrafluo-roethylene. The fluorine NMR spectra of such isolated tetrafluoroethyl groups are characterized by the usual large (54 Hz) two-bond H-F coupling constant (Scheme 6.5). 

When the tetrafluoroethyl group is attached to a carbon bearing hydrogen atoms, the three-bond H-F coupling constants are generally >10 Hz. 2,2,3,3-Tetrafluoropropanol itself is quite inexpensive and... 

Proton and carbon NMR spectra of compounds containing the 1,1,2,2-tetrafluoroethyl and the 2,2,3,3-tetrafluoropropyl groups are exemplified in Scheme 6.5, and the proton and carbon NMR spectra of 2,2,3,3-tetrafluoropropanol are provided as a specific example in Figs. 6.7 and 6.8. 

The antimony(V) chloride catalyzed fluorination with antimony(III) fluoride has been used to prepare (2,2-difluoroethyl)trifluorosilane in 83 % yield from the corresponding trichlorosilyl derivative.88 Also, other trichlorosilanes containing electron-withdrawing fiuorinated alkyl groups (difluoromethyl, 1,1,2,2-tetrafluoroethyl, 1,1-difluoroethyl) arc converted into the corresponding trifluorosilanes in about 80% yield by treatment with the antimony(III) fluoride/ antimony(V) chloride system.89-90... 

Some partially fluorinated tetrazines have been fluorinated28 in the liquid phase, for example, 3,6-bis(l,2,2,2-tetrafluoroethyl)-l,2,4,5-tetrazine (12) gives a number of products, the same product mixture being obtained starting from the compound having an NH-NH rather than an N = N unit. The tetrazine with difluoromethyl groups, instead of 1,2,2,2-tetrafluoroethyl... 

Tetrafluoroethyl)pyridines can be prepared using an unusual reaction of the pyridine oxides with electrophilic fluoroolefins, such as hexafluoropropene (HFP). This reaction discovered by Mailey and Ocone, was further expanded by the Haszeldine group and recently was extensively studied by Makosza et al. The reaction between heterocyclic A-oxides and HFP rapidly proceeds in DMF at ambient temperature and atmospheric pressure, resulting in the formation of the corresponding 2-(l,l,l,2-tetrafluoroethyl)- heterocycles 86-88 (Fig. 7.30). ... 

Line-broadening effects are discernible in the epr spectra of many radicals with a- and / -fluorine atom substituents as shown by the results in Table 14. Fluorine atoms at the radical site cause an increase in the barrier to rotation. Line-broadening effects have been observed for the 1,1-difluoroethyl, and 1,1,2,2,2-pentafluoroethyl radicals and other perfluoroalkyl radicals (67,68,94). No line-broadening effects have been detected, however, for the 1-fluoroethyl or the 1,2,2,2-tetrafluoroethyl radicals (68). A detailed analysis of the epr observations for the 1,1-difluoroethyl radical indicates that rotation of the methyl group is apparently responsible for the line broadening rather than the inversion of the carbon atom center (68,94). Meakin and Krusic also concluded that ro-... 

The in situ polymerization of pyrrole is relatively independent of the substrate. Fabrics produced by inserting a variety of yarns of equal mass into the fill direction and subsequently coated with polypyrrole show only small variations in conductance. Differences in conductance can be seen, however, if the yarn bundle is significantly different in surface area or hydrophobicity (Milli-ken Research Corp., unpublished). Surface polarity may also have an effect on the adhesion of the conducting polymer to the surface of the fiber. Porous fibers produced from polyacrylonitrile or nylon may provide better sites for anchoring to the substrates than more dense crystalline structures such as polyester. Fibers that lack polar groups, such as polyethylene or tetrafluoroethyl-ene, make it more difficult to achieve proper adhesion. Relatively little work has been reported in this field, but generally good adhesion has been observed [44,45]. 

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