Without fluoride

The regiochemistry is determined by the regiochemistry of the fluoride ion addition reaction, that is, via the most stable perfluorocarbanion intermediate Von Werner used a similar reaction to prepare silver compounds from perfluoro-2-methyl-2-butene and perfluoro 2 methyl-2-pentene [271] Silver(I) fluoride adds to bis(ttitluoromethyl)ketene in DMF without fluoride ion catalysis [270] The analogous trifluorovinylsulfurpentafluoride reacts similarly to give the isolable pentafluorosulfur derivative [272] (equation 187)... 

Organotrialkoxysilanes (ArSi(OR)3) were used as organometallic reagents without fluoride additives (Scheme 56).144,144a ArSi(OR)3 was easy to use because of its higher air and moisture stability. Oi and co-workers believed that hydrolysis of the trialkoxysilanes to generate silanetriols was likely occurring prior to transmetallation of the cationic rhodium complex. 

Glucose Values in Blood Collected with and without Fluoride... 

A high sucrose diet promotes decay.11 While most people have some trouble with tooth decay, 1 or 2 per thousand remain totally free of caries and seem to be immune. Many factors must affect resistance to caries. For example, individuals vary in the kinds and numbers of bacteria present on teeth and in the structure of tooth enamel.0 Addition of fluoride ion to water supplies at a level of lppm (0.05 mM) is generally believed to reduce the incidence of tooth decay. However, caries has been declining in many developed countries at rates that are the same for water with or without fluoride.p q If teeth escape caries periodental disease, caused by bacteria, is often a major problem for older people.1... 

Illumination with light having a wavelength larger than the band gap of silicon generates a photocurrent under an anodic potential on an n-Si electrode but has essm-tially no effect on p-Si, as would be expected from the basic theories of semiconductor electrochemistry. However, the photocurrent may not be sustained because of the formation of an oxide film, which passivates the silicon surface to various degrees depending on the electrolyte composition. In solutions without fluoride species, the photocurrent is only a transient phenomenon before the formation of the oxide film. In fluoride solutions, in which oxide film is dissolved, a sustained photocurrent can be obtained. 

Fluoride ions greatly increase the dissolution rate of aluminous minerals. Zutic and Stumm (1984) found that for their rotating disk electrode study of AI2O3 dissolution, the surface reaction was sufficiently rapid to be diffusion controlled at [F ] > 10 M. Pulfer et al. (1984) showed that the rate of dissolution of bayerite was increased by a factor of more than 100 in 10 M fluoride, compared to dissolution without fluoride in 1.0 Af KNO3. Pulfer et al. (1984) stated that the increase in rate was approximately second-order with respect to both [H ] and [F ] in the pH range of 4 to... 

It is well established that the presence of fluoride on a Cr/silica-titania catalyst increases its 1-hexene incorporation efficiency, and lowers the amount of very low-MW material [605]. Table 43 shows one example of this. Two catalysts, Cr/silica and Cr/silica-titania, were activated at 600 °C, with and without fluoride. These catalysts were tested for polymerization activity in the presence of 0.5 mol L 11-hexene. In the absence of titania, no difference was observed in the amount of 1-hexene incorporated into the polymer. However, Cr/silica-titania exhibited a major increase in 1-hexene incorporation when it contained fluoride. 

FIGURE 138 MW distributions of two polymers shown in Table 43. Cr/silica-titania (8 wt% Ti02) with and without fluoride (1.5 F atoms nm 2) was activated at 600 °C, and tested at 95 °C with 0.5 mol L 1 1-hexene. Curves normalized by catalyst activity. 

This phenomenon is rather specific. That is, a Cr/silica catalyst is preferred, not a Cr/silica-titania or a Cr/silica-alumina. It must be activated at a high temperature or treated with fluoride, perhaps to reduce potential ligands. Then it must be reduced in CO. When contacted with some cocatalysts, especially aluminum alkyls, the catalyst then becomes highly sensitive to H2. As illustrated in Table 60, in this series of experiments there was a huge jump in MI only when all of these treatments were combined. Activation at 600 °C does not work unless the catalyst also contains fluoride. Activation at 800 °C is effective without fluoride, but the effect is more pronounced with fluoride. The data shown in Figure 214 illustrate the huge shift in the MW distribution resulting from this combination of catalyst and reaction variables. 

Gedalia, 1., Davidov, I., Lewinstein, 1., and Shapira, L. (1992). Effect of hard cheese exposure with or without fluoride prerinse, on the rehardening of softened human enamel. Caries Res. 26, 290-292. 

Chaik (caicium carbonate) Kaolin Toothpaste (without fluoride)... 

The enhanced reactivity of 3-aminophenylboronic acid in the presence of fluoride was reportedly due to interaction between fluoride and boron. The complexation of fluoride with the boronic acid moiety substantially reduced the oxidation potential required for polymerization, thereby avoiding deleterious side reactions that occur at more positive potentials. The binding of fluoride was confirmed by Fabre et al. [31] with NMR spectroscopy of monomer solution before and after addition of fluoride, since the chemical shift is sensitive to the hybridization of the boron. In monomer solution without fluoride, a NMR signal was observed at 27.7 ppm with reference to borontrifluoride etherate. However, after addition of fluoride, a new signal was observed at 3.4 ppm. The B chemical shift of a tetrahedral boronate formed in the presence... 

Cyclic voltammograms of 3-aminophenylboronic acid in 10 M D-fructose in 10 X PBS without and with fluoride is shown in Figure 3.5. No oxidation of monomer is observed without fluoride in pH 5.0 10 X PBS even in the presence of relatively high D-fructose concentrations (Figure 3.5, a). This is in contrast to the clear oxidation of 3-aminophenylboronic acid under identical conditions in the absence of fluoride and D-fructose (Figure 3.6, a). Similar behavior was observed at pH 7.4, in the absence of fluoride (Figure 3.6, b). However, after... 

Figure 3.6 Cyclic voltammogram of 40mM 3-aminophenyIboronic acid (a) without fluoride and D-fructose in pH 5.0 and (b) with 10 M D-fructose in pH 7.4 10 X PBS at GC electrode. Scan rate lOOmV-s i.

The role of D-fructose, fluoride, and pH in the structure formed with boronic acid has been investigated with NMR spectroscopy of monomer solutions at different pH values in the presence of D-fructose, with and without fluoride. For example, B and F NMR can be used to determine the structure of the boron (neutral trigonal vs anionic tetrahedral) and the involvement of fluoride in the complex (free vs complexed fluoride). The B chemical shift of a tetrahedral boronate appears approximately 20 ppm upfield from the trigonal boronic acid... 

Example 5 Polyaniline-Boronic Acid - Synthesis of Poly(aniline-co-3-amino-phenylboronic Acid)-without Fluoride (5a)... 

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