Bifunctional organosilanes

Bifunctional organosilanes [l-NpRSi(X)Y R = phenyl or ferrocenyl] are good models to study the relative ability of X and Y leaving groups to be displaced. Typical reactions are shown in Table II the data lead to the following conclusions ... 

These experimental facts show mainly parallel chemical and stereochemical data for mono- and bifunctional organosilanes and allow us to conclude that the relative ease of displacement is... 

Bifunctional organosilanes (Table II) lead to the same stereochemical changes when varying the nature of the leaving group. 

Influence of the Leaving Group Behavior of Some Bifunctional Organosilanes... 

TABLE 14. Influence of the leaving group the behaviour of bifunctional organosilanes... 

TABLE 34. Chemical behaviour of bifunctional organosilanes with organometallics influence of an electrophilic assistance... 

Evidence for electrophilic assistance has also been obtained from studies on bifunctional organosilanes, 10. In general, the preference for cleavage with X or Y as the leaving... 

Thin adhesion-promoting layers based on bifunctional organosilanes for iron, zinc, and aluminum with a thickness of about 50-100 nm (Fig. 41b). Especially, van Ooij and coworkers developed various adhesion-promoting systems based on this technology [193-195]. 

In the preceding Sections it was described that chiral phosphine-rhodium complexes are effective in causing stereoselective addition of a hydrosilane to a variety of prochiral carbonyl compounds to give silyl ethers of the corresponding alkanols with fairly high enantiomeric bias at the carbon atom. The present section describes an application of the catalytic asymmetric hydrosilylation of ketones to the preparation of some new asymmetric bifunctional organosilanes. 

The reaction of a bifunctional organosilane with precipitated silica involves the hydrophobation of the alkoxy group of the silane with a surface silanol group of the silica, followed by reaction of the sulfur-containing function of the silane with an olefin group of the elastomer to afford a covalently bonded structure. This silane-coupled silica is useful in improving the abrasion resistance of silicas to levels of carbon blacks, and promoted their use in the treads of radial passenger tires. 

When added to a conventional accelerator/sulphur compound of NR containing 60 pphr precipitated amorphous white silica, the bifunctional organosilane bis(3-triethoxysilylpropyl)tetrasulphane (TESPT) had a profound effect on the viscosity and cure properties. The Mooney viscosity decreased when 7 pphr silane/60 pphr silica was mixed with the compound. The scorch time shortened when 3 pphr silane/60 pphr silica was added to the mix and the optimum cure time was also reduced when 7 pphr silane/60 pphr silica was introduced into the rabber. The rate of cure of the mix accelerated with 7 pphr silane/60 pphr silica. 11 refs. 

The mixing of highly filled silica rabber is discussed with reference to the linking of a bifunctional organosilane to the sihca. The reaction mechanism is investigated for fotrr different silanes for the in-situ modification of sihca. A study is made of the silane reaction following the ethanol formation the influence of the dump temperature, the influence of silane concentration, the silica/silane reaction following the shear modulus tan tones, and consequences for compotmders. 23 refs. 

In the discussion of the loading and curing step, we have focused on the conformation of the silicon side of the aminosilane molecules. Siloxane bond formation and effect of hydrolysis of the alkoxy groups have been characterized clearly. The special reactivity of aminosilanes, compared to other organosilanes, however, is due to the presence of the amino group inside the molecule. The inter- and intramolecular interactions of this group cause special stability and reactivity according to the conditions used. Therefore we will now focus on this side of the bifunctional molecule. 

Morell et al.294 reported on the first syntheses of bifunctional PMOs containing different amounts of aromatic thiophene and benzene bridging groups. Independent of the molar ratios of the organosilanes in the initial reaction mixtures, highly ordered PMO materials were obtained in all cases (Fig. 3.24). 

TESPT, a bifunctional polysulfidic organosilane, was introduced as a coupling agent to improve the reinforcement properties of silicas in rubbers. Use of coupling agents offers the following advantages ... 

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