Methyl orthosilicate

A mixture of methyl orthosilicate 58 (15.2 g, 0.1 mol) and caprylic acid (18.8 g) is heated under reflux for 4 h. The temperature of the boiling mixture drops grad-... 

Between 1925 and 1930 a large number of additional polymers were prepared and characterized as high molecular weight. A list of some of these polymers includes vinyl acetate (71, 72), methyl orthosilicate (73, 74, 75), ethylene oxide (76),... 

Synonyms Tetramethoxysilane tetramethyl orthosilicate methyl orthosilicate tetramethyl silicate... 

So far as is known, the hemolytic and other injurious effects of ethyl and methyl orthosilicates (Chapter 1) must be specific to their... 

SYNS METHYL ORTHOSILICATE METHYL ORTHOSILICATE (DOT) SILICIC ACID, METHYL ESTER of ortho- TETRAMETHOXYSILANE TETRAMETHYL SILICATE TETRAMETHYLSILIKAT TL190... 

METHYL ORTHOSILICATE (681-84-5) Forms explosive mixture with air (flash point 68°F/20°C). Reacts with water, forming methanol and silicic acid. Violent reaction with strong oxidizers, metallic hexafluorides (e.g., molybdenum hexafluorides, tungsten hexafluorides, uranium hexafluorides, etc.). Incompatible with strong acids, nitrates. 

AI3-11596 EINECS 211-656-4 HSDB 5511 Methyl orthosilicate Methyl silicate ((CH3)4Si04) Methyl silicate, ((MeO)4Si) Methyl silicate 28 Methyl silicate 39 MSP 150 NSC 67383 Silane, tetramethoxy- Silicic acid (H4SI04), tetramethyl ester Silicic acid, methyl ester of ortho- Silicic acid, tetramethyl ester SIT 7510.0 Tetra-methyl orfhosilioale Tetramethoxysilane Tetramethyl-silikat TL 190 TMOS TSL 8114 UN2606. Liquid mp = -1.0 bp = 121 d = 1.0232 very soluble in EtOH. 

Synonyms/Trade Names Methyl orthosilicate. Tetramethoxysilane, Tetramethyl ester of silicic acid. 

Methyl orthosilicate. See Tetramethoxysilane Methyloxacyclopropane. See Propylene oxide... 

Nicolaon GA, Teichner SJ (1968) Preparation of silica aerogels from methyl orthosilicate in alcoholic medium, and their properties. Bull Soc Chim Er 1906-1911... 

The various methods of preparing monosilicic acid may be summarized as follows. A saturated solution of monosilicic acid, SifOH), containing about 0.01% SiOj, is obtained when pure amorphous silica is equilibrated with water at room temperature. A more concentrated (supersaturated) solution can be obtained only indirectly by liberating monosilicic acid from its compounds under carefully controlled conditions at low temperature and low pH, dilute solutions remain supersaturated with respect to amorphous silica for appreciable periods. For example, at pH 3 and 0°C, solutions of monosilicic acid up to O.l (0.6% SiOj) can be prepared by spontaneous hydrolysis of monomeric silicon compounds, sich as silicon tetrachloride or methyl orthosilicate, and also by reacting monomeric silicates, such as sodium or magnesium orthosilicates or hydrated crystalline sodium metasilicate, with dilute acid. 

Measurements on a system containing extremely pure silica by Schwartz and Muller (33) give a still more precise value of pAfa 9.91 0.04. They hydrolyzed extremely pure methyl orthosilicate in water in a system which rigorously excluded atmospheric impurities, to obtain solutions containing from 12.4 to 155 ppm SiOj. The conductivity and pH were measured with precision at 25 C using low frequency alternating current. From the initial conductivities the value of the acidity constant was calculated. 

Such a case may be involved in the observations of Schwartz and Muller (33), who made a highly purified solution of silicic acid from methyl orthosilicate at concentrations up to 150 ppm. Initially, conductivity measurements indicated that the silica was monomeric, but after half an hour the conductivity, at all concentrations, slowly-decreased to about half the original value. This happened even though in half the samples the concentrations were less than the solubility of amorphous silica. It was assumed that the monomer polymerized slowly at pH 7 to a polymer species that is smaller than usual colloidal dimensions, since it passed through an ultrafiler, yet it must be more insoluble than amorphous silica. 

Figure 3J8. Limited polymerization of monosilicic acid (0.8% SiOz) from hydrolyzed methyl orthosilicate in dilTerent hydrolysis and aging media at 25 C. Molecular weight number average as SiO. Curve 1. 10 N HCI Curve 2. 10 N HCI Curve 5, 10 N H S04. [From Schwarz and KnaufT(2l).]...

Monosilicic acid can be prepared from the silicate-acid system, just as from the silicon tetrachloride-water or methyl orthosilicate-water systems [746]. Acetic acid or resin exchangers in the H-form can be added to dilute solutions of sodium silicate. Monosilicic acid is formed by reaction of solid calcium orthosilicate with hydrogen chloride in methanol, according to the equation ... 

Purest polysilicic Hydrolysis of purified methyl orthosilicate with excess... 

The alkoxides, Si(OR) such as tetraethyl orthosilicate (TEOS), Si(OC2Hj) or tetra-methyl orthosilicate (TMOS), Si(OCHj) are the well started precursors in the sol-gel formation. Alkoxides are ideal chemical precursors for sol-gel synthesis because they react readily with water, in which the hydrolysis of Si atom takes place to form a hydroxytriethyl orthosilicate or a hydroxytrimethyl orthosilicate.The reaction is called hydrolysis, because a hydroxyl ion becomes attached to the silicon atom as follows ... 

---