Silicic esters

Silicate [12627-13-3] Silicate adhesives Silicate esters Silicate grouts Silicate minerals Silicates... 

Silicate Esters. Silicate esters, Si(OR)4 where R is an aryl or alkyl group, have excellent thermal stability, and using proper inhibitors, show... 

Silicate esters are used ia the production of coating and refractories and in some semiconductor manufacturing operations. A broad range of purity grades of silicon tetrachloride are available to meet the requirements of these different appHcations. 

Viscosity is defined as the shear stress per unit area at any point in a confined fluid divided by the velocity gradient in the direc tiou perpendicular to the direction of flow. If this ratio is constant with time at a given temperature and pressure for any species, the fluid is caUed a Newtonian fluid. This section is limited to Newtonian fluids, which include all gases and most uoupolymeric liquids and their mixtures. Most polymers, pastes, slurries, waxy oils, and some silicate esters are examples of uou-Newtouiau fluids. 

Acid derivatives that can be converted to amides include thiol acids (RCOSH), thiol esters (RCOSR), ° acyloxyboranes [RCOB(OR )2]. silicic esters [(RCOO)4Si], 1,1,1-trihalo ketones (RCOCXa), a-keto nitriles, acyl azides, and non-enolizable ketones (see the Haller-Bauer reaction 12-31). A polymer-bound acyl derivative was converted to an amide using tributylvinyl tin, trifluoroacetic acid, AsPh3, and a palladium catalyst. The source of amine in this reaction was the polymer itself, which was an amide resin. 

Bonded phases have been prepared by other general methods besides those indicated so far [64-66]. Reaction of silica with an alcohol or isocyanate resulted in the formation of silicate esters (estersils), but these phases were too hydrolytically unstable to be generally useful. Bonded phases with an Sl-R or Sl-NHR structure are more hydrolytically stable than the estersils but... 

The chemistry of silicone halides was recently reviewed by Collins.13 The primary use for SiCU is in the manufacturing of fumed silica, but it is also used in the manufacture of polycrystalline silicon for the semiconductor industry. It is also commonly used in the synthesis of silicate esters. T richlorosilane (another important product of the reaction of silicon or silicon alloys with chlorine) is primarily used in the manufacture of semiconductor-grade silicon, and in the synthesis of organotrichlorosilane by the hydrosilylation reactions. The silicon halohydrides are particularly useful intermediate chemicals because of their ability to add to alkenes, allowing the production of a broad range of alkyl- and functional alkyltrihalosilanes. These alkylsilanes have important commercial value as monomers, and are also used in the production of silicon fluids and resins. On the other hand, trichlorosilane is a basic precursor to the synthesis of functional silsesquioxanes and other highly branched siloxane structures. 

Acid derivatives that can be converted to amides include thiol acids RCOSH, thiol esters RCOSR,911 acyloxyboranes RCOB(OR )2,912 silicic esters (RCOO)4Si, 1,1,1-trihalo ketones RCOCX3,913 a-keto nitriles, acyl azides, and nonenolizable ketones (see the Haller-Bauer reaction 2-33). 

Much of the early work on the synthesis of organosilicon compounds was based on reactions between Grignard reagents and silicon halides (and to a lesser extent on silicate esters), and much effort was devoted to optimizing stepwise reactions ... 

It is true that straw and feathers contain silicon, for its oxide is found in the ash when these materials are burned, but the mechanism by which this silicon entered into the plant or animal is not understood, and it has not been demon-strated that silicate esters or organosilicon compounds are involved. 

Besides hydrolysis, the silicic esters show many more of the reactions which have been described for the halides. For example, the alkoxy group reacts with the Grignard reagent to attach organic groups directly to the silicon atom in stepwise fashion ... 

A variation of the method was described in 1884 by Pape, who used a mixture of silicon tetrachloride and propyl iodide with metallic zinc instead of preparing the zinc dipropyl separately. Another variation, exploited by Friedel and Ladenburg, eliminated the sealed tube by introducing metallic sodium along with the zinc alkyl and silicate ester ... 

Cymene or isopropyltoluene is produced via alkylation of toluene with propylene. Cymene is an important intermediate in the production of cresol, and it is also used as an industrial solvent. Again, for both environmental and economic reasons, the use of zeolitic materials for this conversion has been studied. For example, Flockhart et al. have used zeolite Y to effect this reaction (7). They observed that the state of the zeolite, including its degree of ion-exchange and the temperature at which it was calcined, strongly affected the distribution of cymene isomers obtained. In order to enhance the selectivity to para-cymene, the direct precursor to para-cresol, various studies have focused on the use of surface modified zeolites, for example, ZSM-5 materials, including those produced by chemical vapor deposition (CVD) of silicate esters. These species serve to reduce surface acidity and change limit diffusion within the crystal. 

All four elements form alkoxides, but those of silicon, for example, S OQHs), often called silicate esters, are the most important the surface of glass or silica can also be alkoxylated. They can be used in the synthesis of ceramic materials.71 Alkoxides are normally obtained by the standard method ... 

Both one-component and two-component silicone sealants contain polydimethyl siloxane as the base polymer along with fillers such as calcium carbonate and/or fumed silica fillers, plasticisers (silicone oil) and a variety of cross-linking agents and adhesion promoters. Two-component sealants utilise a catalyst such as dibutyl tin dilaurate, alkyl silicate esters and metallic salts (Maslow, 1982). 

Compounds 3 and 18 - 20 have been prepared to combine luminescent semiconductors with curable units. The transformation of the monomeric compounds to siloxanes of higher molecular weight was performed by hydrolysis of the silicic esters in chloroform/ethanol solution, catalyzed by traces of hydrochloric acid for 2 days (Scheme 4). 

Sea Water Silicate Esters Silver Nitrate Fle-CeoMeo B HI u u Henchei Cel. Fonron 40% pl.fIP. 

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