Ethoxysilane

WATER - WATERPROOFING AND WATER/OIL REPELLENCY] (Vol 25) -ethoxysilanes for [SILICON COMPOUNDS - SILICON ESTERS] (Vol 22)... 

Further examination has shown that the acid content should be small in order for the solution to become spinnable in the course of hydrolysis and polycondensation. It has been found (4 ) that very large concentrations at more than 0.15 in the [HCl]/[Metal alkoxide] ratio of acid catalyst produce round-shaped particles in the tetra-ethoxysilane (7) and tetramethoxysilane solutions, and so no spinnability appears. 

There are reactive softeners, some of which are N-methylol derivatives of long-chain fatty amides (10.241) while others are triazinyl compounds (10.242). The N-methylol compounds require baking with a latent acid catalyst to effect reaction, whereas dichloro-triazines require mildly alkaline fixation conditions. The N-methylol compounds are sometimes useful for combination with crease-resist, durable-press, soil-release and water-repellent finishes. In this context, the feasibility of using silane monomers such as methyltri-ethoxysilane (10.243), vinyltriethoxysilane (10.244), vinyl triace tylsilane (10.245) and epoxypropyltrimethoxysilane (10.246) in crosslinking reactions to give crease-resist properties and softness simultaneously has been investigated [492]. 

This method of silanation, which uses organic solvent without the addition of water, is suitable for highly reactive silane derivatives, such as chlorosilanes, aminosilanes, and methoxysilanes. This procedure will not work for ethoxysilanes, as these compounds are not reactive enough without prior hydrolysis to create the silanol. This method is convenient to use for silica particle modification and for the functionalization of metallic nanoparticles having the requisite—OH groups present (see Chapter 14, Section 5). 

FIGURE 13.6 Calibration plot for hydrogen peroxide detection in flow-injection mode with nano-struc-tured Prussian blue as a detector Prussian blue electrodeposited through sol template based on the vinyltri-ethoxysilane, operating potential 50 mV, phosphate buffer pH 6.0 + 0.1M KC1, flowrate 0.7ml/min. 

The sol-gel process involves hydrolysis of alkoxide precursors under acidic or basic conditions, followed by condensation and polycondensation of the hydroxylated units, which lead to the formation of porous gel. Typically a low molecular weight metal alkoxide precursor molecule such as tetramethoxy silane (TMOS) or tetra ethoxysilane (TEOS) is hydrolyzed first in the presence of water, acid catalyst, and mutual solvent... 

Abbreviations TMOS tetramethoxysilane, MTMS methyl-triethoxysilane, Cjg-TMSPAC octadecyldimethyl [3-(trimethoxysilyl)propyl] ammonium chloride, PheDMS phenyldimethylmethoxysilane, TEOS tetraethoxysilane, Cg-TEOS -octyltriethoxysilane, APTES aminopropyltri-ethoxysilane, PTES phenyltriethoxysilane, allyl-TrMOS allyltriethoxysilane, DOS diglycerylsilane, Cg-TMOS n-octyltrimethoxysilane. 

Synonyms Tetraethyl orthosilicate tetra-ethoxysilane ethyl orthosilicate silicic acid, tetraethyl ester... 

Kolesar GB, Siddiqui WH, Geil RG, et al Subchronic inhalation toxicity of tetram-ethoxysilane in rats. Fundam Appl Toxicol 13 285-295, 1989... 

Condensation of diethyl difluorosilane with 100% hydrogen peroxide in the presence of ammonia results in the formation of ethoxysilane, whereas an analogous condensation with diethyl dichlorosilane produces polymeric peroxides containing ethoxy and siloxane units. The initially formed straight chain or cyclic peroxides probably rearrange to products 3 or 4 containing alkoxy and siloxane moieties (equation 5) . 

Tetraalkoxysilanes (usually tetramethoxysilane, TMOS, bp 121 °C, or tetra-ethoxysilane, TEOS, bp 169 °C) for hydrolytic gelling can be made by reaction of SiCl4 (Section 17.8.2) with the relevant alcohol ... 

Ethanol when added directly to the PTES/TEOS mixture is thus highly favoring the formation of a hexagonal phase with respect to the cubic phase. However, even if ethanol is not directly added to the precursor mixture, it is produced during the synthetic procedure via hydrolysis and condensation reactions of PTES and TEOS. One can now wonder which results will be obtained if methoxysilanes rather than ethoxysilanes are used. 

The alcoholysis reaction involves the acid-catalyzed exchange of an ethoxy group for a methoxy group on various ethoxysilanes. The progress of the reaction was followed by measuring the disappearance of the ethoxysilane vs. an internal standard (mesitylene). Response factors for each of the ethoxysilanes... 

While attempts were made to prepare the ethoxysilanes via the classic Grignard reaction, only phenyldimethylethyoxysilane was prepared in this manner. The Grignard reaction proved to be unsuitable for the preparation of the four para-substitutcd phenyldimethylethoxysilanes either because of sensitivity to Grignard formation or difficulty in isolating the product from the reaction mixture since the by-product salts were unfilterable. Therefore, all four silanes (p-chlorophenyl, p-methoxyphenyl, p-tolyl and p-trifluoromethylphenyldimethyl-ethoxysilane) were prepared via an organolithium reaction. 

The kinetic reactions for the alcoholysis study were carried out by mixing one of the para-substituted ethoxysilanes with a solution containing methanol, dichloroacetic acid and an internal standard, keeping the reaction mixture at 25°C in a constant temperature bath ... 

Cg and C", are the initial concentrations of ethoxysilane an methanol, respectively. The two different data treatments gave essentially identical values of k. Dividing k by the concentration of the dichloroacetic acid yields the rate constant, k, for the reaction. Table 6 contains the rate data for each of the alcoholysis reactions of the p-substituted phenyldimethylethoxysilanes. 

---