Electronegative fluorine

The elimination of water from a fluorinated compound generally follows a reaction path similar to that of its nonfluorinated counterpart, although the presence of the highly electronegative fluorine atoms may have unexpected effects Various monofluoro alcohols can be dehydrated via their tosyl esters at 75 C by using potassium rert-butoxide [80] (equation 50)... 

Iodide ions reduce Cu to Cu , and attempts to prepare copper(ll) iodide therefore result in the formation of Cul. (In a quite analogous way attempts to prepare copper(ll) cyanide yield CuCN instead.) In fact it is the electronegative fluorine which fails to form a salt with copper(l), the other 3 halides being white insoluble compounds precipitated from aqueous solutions by the reduction of the Cu halide. By contrast, silver(l) provides (for the only time in this triad) 4 well-characterized halides. All except Agl have the rock-salt structure (p. 242). Increasing covalency from chloride to iodide is reflected in the deepening colour white yellow, as the... 

The designation of hard acids is not restricted to metal cations. For example, in BF3 the small boron atom in its +3 oxidation state is bonded to three highly electronegative fluorine atoms. All the B—F bonds are polarized away from a boron center that is already electron-deficient. Boron trifiuoride is a hard Lewis acid. 

There is little information for fluoro-substituted sulfinyl groups. Values of a and ffp for SOCFj based on benzoic acid ionization are 0.63 and 0.69 respectively , compared with values of about 0.52 and 0.49 for SOMe (Table 3). Thus the electronegative fluorine somewhat enhances the electron-attracting influence of the sulfinyl function and makes the order more definitely sulfur lone pair to engage in 7t(pp) conjugation. Values of and ffp for SOCF3 based on anilinium ion dissociation are 0.76 and 1.05 respectively . An increase of 0.13 as between and [Pg.509]

On the one hand, Fig. 10.2 exhibits iso surfaces around the fluorine atoms on the other hand the lone electron pairs at the central atoms can be discerned quite well. The space requirement of one lone pair is larger than that of the four electron pairs at one of the more electronegative fluorine atoms. The three lone pairs at the chlorine atom of ClFj add up to a rotation-symmetrical torus. 

The distribution of negative charge around the electronegative fluorine is... 

A very important group of secondary hydroxyl modifications represent fluoroglycosides.104 When they interact with a retaining glycosidase, the highly electronegative fluorine on the carbohydrate ring causes the destabilization of both transition states and the reaction proceeds at a... 

Electronegativity refers to tendency of an atom to pull electrons towards itself in a chemical bond. Nonmetals have high electronegativity, fluorine being the most electronegative while alkali metals possess least electronegativity. Electronegativity difference indicates polarity in the molecule. 

By placing a CF3 substituent at the / ara-position of 20, the interaction of Na+ with the highly electronegative fluorine atoms shifts the binding site closer to the CF3 functionality (see structures in Figure 4). The distance between the Na+ and the double bond of the alkene is higher, therefore, and the stabilizing electrostatic interaction between... 

In this case the electropositive sodium atom loses its 3s electron, which is then transferred to the 2p orbital of the electronegative fluorine atom to produce the Na+F ion-pair. Ionic bonding is the subject of Chapter 7. When there is little or no difference in the electronegativity coefficients of the combining atoms, covalent bonds are possible in which two or more electrons are shared between the two atoms. Covalency is the main subject of this chapter. 

Answer. Two factors contribute to the stabilization of carbanions by an adjacent trifluoromethyl group or other perfluorinated groups. Most obviously, the strong inductive effect of the highly electronegative fluorine atoms will tend to increase the... 

This initial hypothesis was subsequently refined by the deduction of two preference rules for the structures of the intermediate pentacovalent phosphorus derivatives, the phosphoranes. Muetterties and Schunn65. in order to rationalize the nmr spectra of a number of alkyl fluorophosphoranes (CH3) -PF5 . formulated the hypothesis that the more electronegative fluorine atoms... 

As noted above, the hardness or softness of an acidic or basic site is not an inherent property of the particular atom at that site, but can be influenced by the substituent atoms The addition of soft, polarizable substituents can soften an otherwise hard center and the presence of electron-withdrawing substituents can reduce the softness of a site. The acidic boron atom is borderline between hard and soft. Addition of three hard, electronegative fluorine atoms hardens the boron and makes it a hard Lewis acid. Conversely, addition of three soft, electropositive hydrogens54 softens the boron and makes it a soft Lewis acid. Examples of the difference in hardness of these two boron acids are... 

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