Silanes triethoxysilanes

In [276] the properties of kaolin-filled polyethylenes were investigated. The filler was pre-treated with silanes of two kinds, vinyl triethoxysilane (VTES) (I) and gamma-methacryloxypropyl trimethoxysilane (II). The results are presented in Table. 9. 

Rh colloids were isolated during the hydrosilylation of trimethy(vinyl)silane with triethoxysilane using RhCl3 in EtOH as pre-catalyst. The colour changes observed during the catalytic reaction (from yellow, to red and black) are due to the formation of colloids as demonstrated by TEM this fact was in agreement with the catalytic activity behaviour observed [14]. 

This test was successfully applied for the hydrosilylat-ion of trimethyl(vinyl)silane by triethoxysilane catalysed by Rh or Pt colloids. The addition of mercury to catalytic mixture led to catalytic activity loss, consistent with a heterogeneous catalyst [12,14]. 

The hydrogenation of alkenes and alkynes in water can also use silanes as hydrogen sources. Tour reported that by using palladium acetate as catalyst, triethoxysilane reduced C-C unsaturated bonds to saturation in a mixture of THF and water.18 The reaction showed excellent chemo- and stereoselectivity. Water was essential to the reaction. In the absence of water, 95% of the starting alkene remained unchanged (Eq. 3.3). 

It is also worthwhile to outline at this place the immobilization procedure that was used for the preparation of type I CSPs A bifunctional linker with a terminal isocyanate on one side and a triethoxysilyl group on the other end (3-isocyanatopropyl triethoxysilane) was reacted with the native cinchona alkaloids quinine and quinidine and subsequently the resultant carbamate derivative in a second step with silica [30], Remaining silanols have been capped with silane reagents, yet, are less detrimental for acidic solutes because of the repulsive nature of such electrostatic interactions. CSPs prepared in such a way lack the hydrophobic basic layer of the thiol-silica-based CSPs mentioned earlier, which may be advantageous for the separation of certain analytes. 

In a typical reaction, the macrocycle is treated with a 2-3 M excess of (3-isocyanatopropyl)triethoxysilane in dry DMF. The derivative is then added to a dry DMF slurry of silica gel ( 2 g of functionalized selector to 4 g of silica gel). The solution is stirred, allowed to react for 20 h at 107°C, and then cooled, filtered, and washed with methanol, 50% aqueous methanol, and methanol again, and finally dried. Surface coverage data are reported only in the case of the commercially available vancomycin CSP (see Table 2.2), immobilized by joining on average three linkers per vancomycin molecule, probably via a 3-isocyanatopropyl-silane [48]. 

Culler, S.R., Ishida, H. and Koenig, J.L. (1986). The silane interphase of composites effects of process condition on y-aminopropyl triethoxysilane. Polym. Composites 7, 231-238. 

Covalent immobilization methods of NAs to a silica surface require its chemical modification. Functionally inert surface silanols (Si - OH) need to be transformed into reactive species to which the NAs can be attached irreversibly. To date, the main method for the attachment of biological moieties to silica surfaces has involved substrate reaction with organofunctional silanes of the general structure (RO)3Si(CH2)X, followed by the covalent attachment of the biological molecule to the newly introduced fimctional group on the surface [31,32]. Examples of organofimctional silanes used this way include (3-glycidoxypropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane,... 

Fig. 9 Silanization of silica siufaces with aminopropyl(triethoxysilane). In (i) the reactive groups of the triethoxysilane are hydrolyzed by water, followed by condensation (ii) with the surface and (iii) thermal curing of the film, which further cross-links the free silanol groups...

Shibata and co-workers have reported an effective protocol for the cyclization/hydrosilylation of functionalized eneallenes catalyzed by mononuclear rhodium carbonyl complexes.For example, reaction of tosylamide 13 (X = NTs, R = Me) with triethoxysilane catalyzed by Rh(acac)(GO)2 in toluene at 60 °G gave protected pyrrolidine 14 in 82% yield with >20 1 diastereoselectivity and with exclusive delivery of the silane to the G=G bond of the eneallene (Equation (10)). Whereas trimethoxysilane gave results comparable to those obtained with triethoxysilane, employment of dimethylphenylsilane or a trialkylsilane led to significantly diminished yields of 14. Although effective rhodium-catalyzed cyclization/hydrosilylation was restricted to eneallenes that possessed terminal disubstitution of the allene moiety, the protocol tolerated both alkyl and aryl substitution on the terminal alkyne carbon atom and was applicable to the synthesis of cyclopentanes, pyrrolidines, and tetrahydrofurans (Equation (10)). 

Triethoxysilane, HSi(OC2H5)3. The silane is prepared industrially by ethanolysis of trichlorosilane. 

Trichlorobenzoyl chloride, 552 Trichloroethylene, 552-553 Trichloroiodosilane, 466 Trichloromethylarenes, 119 Trichloro methyl)silane, 553 Trichlorosilane-Triethylamine, 553-544 Tricholomic acid, 188 Triethoxysilane, 554... 

After etching, bonding of an organic moiety to the etched inner wall for the stationary phase takes place using the silanization/hydrosilation process adapted for the capillary format [18-20], This approach for attaching a variety of organic moieties to silica involves first silanizing the surface by reaction with triethoxysilane (TES) to create a hydride intermediate [21] as shown in equation 7.1. 

Besides, the synthesis of rectification of the obtained products may be accompanied by certain by-processes, when the unreacted triethoxysilane is disproportioned to tetraethoxysilane and silane (Sil I4). 

Like a,/Lunsaturated carbonyl compounds, vinyl silanes and particularly vinylsiloxanes do not dimerise readily and can thus be used in excess to drive selective CM reactions. Pietraszuk et al. [56] have exploited this to couple vinyl-triethoxysilane with a variety of olefin partners in good yield and with high stereoselectivity (Scheme 8) [57]. Given the importance of vinylsiloxanes as nucleophilic components in Pd-catalysed coupling reactions [58], their facile and stereoselective modification by CM is a significant development. 

Recently Ru3(CO)12 has been reported to be an effective catalyst for hydrosilylation of 1-octene [10] and of allyl chloride (Eq. 3) [11] by triethoxysilane.The latter process is of great importance for production of the main intermediate in manufacturing silane coupling agents. 

As we have already mentioned, ruthenium complexes predominantly catalyze the dehydrogenative silylation of alkenes but competitively with the hydrosilylation so the reaction usually gives a mixture of the dehydrogenative silylation and hydrosilylation products. Ru3(CO)12 appears to be a very active catalyst for the dehydrogenative silylation of styrene, para-substituted styrenes [ 19, 20],trifluoropropene and pentafluorostyrene [21] by trialkyl-, phenyldialkyl-silanes (but also triethoxysilane) (Eq. 10). 

Adsorbed films of ethykriethoxysilane and vinyltriethoxy-silane were formed on silica and alumina by retraction from hydrocarbon solution and their wettabilities and water-stabilities determined. The vinyltriethoxysilane films were generally more oleophobic, more hydrophobic and more resistant to contact with water than the films formed by the ethyl analog. Neither adsorbate formed stable films on a-alumina. The addition of low molecular weight organic acids or bases to the adsorbate solution resulted in both the ethyl and vinyl compound forming hydrophobic and water-stable films on silica and ot-alumina. Films of p-chloro-phenyl-ft-ethyltrichloro, -trimethoxy, and -triethoxysilane were also studied and found to be water-stable and to have wettabilities characteristic of a surface comprised of closely-spaced p-chlorophenyl groups. 

The presence of surface OH groups or H2 O molecules can play a primary role in adsorption. For example, a microcalorimetric study of the adsorption of stearic acid, from heptane solution, on ferric oxide (Husbands et al., 1971) revealed that preadsorbed water enhanced adsorption of stearic acid. When adsorption takes place from a dry organic liquid, residual surface water may act as special agent. This was shown for the adsorption of a silane coupling agent (y-amino-propyl-triethoxysilane) on silica covered with water molecules for 6 < 1 (Trens and Denoyel, 1996). By the simultaneous determination of adsorption isotherms and the enthalpies of displacement (of heptane by various silanes) it was demonstrated that the amine function was able to displace some of the surface water and make it available for the hydrolysis of the silane into trisilanol, whereas the residual water was able to promote the formation of siloxane bonds between the trisilanol molecules and the surface. 

Fig. 13 Commonly applied silanes in glass modification (1) 3-aminopropyltriethoxysilane (2) glycidopropyltrimethoxysilane (3) 3-mercaptopropyl-triethoxysilane (4) 4-trimeth-oxysilyl-benzaldehyde (5) triethoxysilane undecanoic acid (6) bis (hydroxyethyl) amino-propyltriethoxy-silane (7) 3-(2-aminoethylamino) propyltrimethoxysilane...

In this section, we discuss the photo-orientation of azobenzenes in molecularly thin SAMs by means of UV-vis spectroscopy and surface plasmons (SPs). The structural formula of 4-(6-carboxy-(3-amidopropyl)triethoxysilane)-4 -pentylazobenzene, referred to as azo-silane, which leads to a self-assembled monolayer, is shown in Figure 4.1 (top). Azo-silane SAMs (see schematic in Figure 4.1, bottom) for the UV-vis spectroscopy and surface plasmons experiments were prepared as reported elswhere. ... 

The aim of this work was to examine the catalytic activity of rhodium siloxide complexes in the hydrosilylation of allyl glycidyl ether by triethoxysilane and hydro(poly)siloxanes, leading to optimization of procedures for the synthesis of epoxy-functional silanes and siloxanes. 

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