Fluoroalkyl groups

MAI composed of PAIE for application to emulsifiers, drug carriers, and ion-exchange resins [60,61]. Poly(per-fluoropropyleneglycol)-b-poly(acrylic acid) was synthesized initiated with an MPI having fluoroalkyl group in the main chain [62]. It was soluble to water, ethanol, and THF, and showed water repellency, oil repellency, antifouling, and resistance to chemicals. 

Sigaud G, Nguyen HT, Achard MF, Twieg RJ (1990) Phys Rev Lett 65 2796 and references cited therein. We note that alkyl and fluoroalkyl groups are nonpolar and interact primarily via dispersion (Van der Waals) forces Vru-aF H- Thus the... 

Polyfluorinated chemicals now dominate in the fields of oil-repellent and water-repellent finishes. The earlier so-called conventional polyfluorinated products were of the type represented by poly(N-methylperfluoro-octanesulphonamidoethyl acrylate) (10.248) [499]. Such products presented a shield of closely packed fluoroalkyl groups at the fibre-air interface, thus giving low-energy surfaces with excellent oleophobicity. These showed excellent resistance to oil-based stains but were less satisfactory as soil-release agents during... 

To improve the solvent resistance of the polymer, a fluoroalkyl group can be substituted on each silicon atom for one of the methyl groups, the resultant polymer (ISO designation FMQ or FVMQ) having the following repeat unit. 

Another series of experiments has been performed using simple ketones substituted by fluoroalkyl groups. In this way it is clearly shown that the presence of a perfluorine group adjacent to the carbonyl to be hydrogenated is essential in order to provide both excellent activities and enantioselectivities (Table 33.9). 

Anodic Oxidation of Heteroatom Compounds Having Fluoroalkyl Groups... 

Here, regioselective anodic substitutions of heteroatom compounds having fluoroalkyl groups and the effects of fluorine atoms on both the synthetic behavior and the oxidation potentials will be mainly discussed. 

A linear correlation of the oxidation potentials Bp of sulfides with Taft s a values of fluoromethy] groups is obtained as shown in Fig. 1 [42]. This dearly indicates that the polar effect of the fluoroalkyl group plays a significant role in the electron-transfer step from the sulfides to anode. Namely, the oxidation potential increases linearly as the number of fluorine atoms of the fluoroalkyl group increases. However, interestingly the oxidation potential was not appreciably affected by the length of the perfluoroalkyl group (Table 4). 

On the contrary, the anodic acetoxylation is markedly promoted by per-fluoroalkyl groups (Eq. 27) [46]. It is notable that the promotion effect of a CF3 group on the anodic methoxylation is more pronounced than that of a CN group although the CF3 group has a smaller electron-withdrawing effect than CN. 

Unlike the approach in which LB multilayers are formed from polymerizable fluoromonomers followed by UV-polymerization,69 we started to use functional fluoropolymers for the preparation of LB films. These films seem to be better, because in the case of monomeric LB film the polymerization process causes contraction and hence possible defects in the final cured film. Two different kinds of functional amphiphilic fluoropolymers were used for LB-film preparation. One type (referred to in Section 7.4.2), which has large fluoroalkyl groups as side... 

It is interesting to note that Saunders, Stacey, Wild and Wilding6 have brought about the reaction between triethyl phosphite and bromofluoroethane (II), giving diethyl 2-fluoro-ethylphosphonate (HI), thus providing the first recorded example of the 2-fluoroalkyl group attached to phosphorus ... 

C. Jackel, M. Salwiczek, B. Koksch, Fluorine in a native protein environment—How the spatial demand and polarity of fluoroalkyl groups affect protein folding, Angew. Chem. Int. Ed. 45 (2006) 4198-4203. 

Fluorination has an important indirect impact on hydrogen bonds, via neighbouring functions (hydroxyl, amine, carbonyl, hydrogen). The electron-withdrawing effect of fluorine atom and of fluoroalkyl groups (CF2, CF3, etc.) deeply modifies the pKg of neighbouring functions, and hence their character of hydrogen bond donors or acceptors (Table 1). 

In aromatic series, when hydrogen atoms are replaced by fluorine atoms or by fluoroalkyl groups, an enhancement of the log P occurs (Table 3) [13]. The CF3, CF3O and CF3S groups are the most hydrophobic substituents known. They are widely used in crop science [41]. 

Stabilisation of the tetrahedral forms of fluoroalkyl ketones The presence of a fluoroalkyl group in a position of a carbonyl strongly enhances its electrophilicity, and hence its reactivity, towards nucleophiles. The anionic tetrahedral intermediates are stabilised by the electron-withdrawing group Rf (Fig. 20) [69,70]. This phenomenon is illustrated by the ability of fluoroketones to afford stable hydrates in aqueous medium. 

Figure 3.9 Influence of a fluoroalkyl group on the inhibition of HNE and the activity of peptidyl fluoroalkyl ketones. ...

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