681-84-5 Usage
Description
Tetramethyl orthosilicate is the chemical compound with the formula Si(OCH3)4. This molecule consists of four methoxy groups bonded to a silicon atom.Two common organic precursors are tetraethyl orthosilicate (TEOS) and tetramethyl orthosilicate (TMOS). The latter is more toxic than the former.Tetraethyl orthosilicate (TEOS), Si(OC2H5)4, is the first alkoxide of the series, followed by tetramethyl orthosilicate (TMOS), Si(OCH3)4, which is, however, less safe to handle and hydrolyzes faster than TEOS.The hydrolysis of TMOS is, in fact, around six times faster: in general, a lower hydrolysis rate is associated with an increase of the organic group size in the silicon alkoxide. The properties of the silicon alkoxides change according to the dimension of the alkoxy; larger groups produce an increase in molecular weight, viscosity, and boiling point and a decrease in density of the alkoxides.As a rule of thumb, a larger size of the alkoxy group is associated with a lower hydrolysis rate due to the steric hindrance. The reactivity follows the sequence, with tetramethyl orthosilicate the most reactive alkoxide:tetramethyl orthosilicate >tetraethyl orthosilicate>tetra-n-propylorthosilicate>tetrabutyl orthosilicate
Chemical Properties
Tetramethyl orthosilicate (TMOS), the methyl ester of orthosilicic acid, is a colorless, low-viscosity liquid. It is industrially the most important of the tetraalkyl silicates.
Uses
Different sources of media describe the Uses of 681-84-5 differently. You can refer to the following data:
1. Tetramethyl orthosilicate (TMOS) is popularly used in the sol-gel synthesis of silicates1 and chromium-doped silicates and in the formation of hexagonal mesoporous silica layers.
2. Coating screens of television picture
tubes; mold binders; corrosion-resistant coatings;
catalyst preparation; silicone intermediate
3. Tetramethyl Orthosilicate is a compound used in the research of the multifunctionality of silicified nanoshells and the efficiency at adsorbing cadmium ions at cell interfaces.
Production Methods
Silica aerogels are usually prepared by base-catalyzed reaction
of tetramethoxysilane or tetraethoxysilane, mostly with
ammonia as the catalyst. A modification of this procedure is
to prehydrolyze Si(OR)4 with a small amount of water under
acidic conditions.
General Description
A clear colorless liquid. Flash point below 125°F. Less dense than water and insoluble in water. Very toxic by ingestion and inhalation and very irritating to skin and eyes. Used to make paints and lacquers.
Air & Water Reactions
Flammable. Insoluble in water.
Reactivity Profile
Tetramethyl orthosilicate is incompatible with the following: Oxidizers; hexafluorides of rhenium, molybdenum & tungsten .
Hazard
Eye damage and upper respiratory tract irri-tant.
Health Hazard
TOXIC; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance may cause severe injury, burns or death. Bromoacetates and chloroacetates are extremely irritating/lachrymators. Reaction with water or moist air will release toxic, corrosive or flammable gases. Reaction with water may generate much heat that will increase the concentration of fumes in the air. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.
Fire Hazard
HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors form explosive mixtures with air: indoors, outdoors and sewers explosion hazards. Most vapors are heavier than air. They will spread along ground and collect in low or confined areas (sewers, basements, tanks). Vapors may travel to source of ignition and flash back. Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff. Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water.
Flammability and Explosibility
Flammable
Safety Profile
Poison by
intraperitoneal route. Moderately toxic by
inhalation. Midly toxic by skin contact. A
severe eye irritant. This material can cause extensive necrosis (experimentally),
keratoconus, and opaque cornea. It also
causes severe human eye injuries, as well as
necrosis of corneal cells, which progresses
long after exposure has ceased. It is
destructive and its effects resist treatment.
Permanent blindness is possible from
exposure to it. The kidney seems to be most
subject to injury regardless of the mode of
exposure. Pulmonary edema has also
occurred. This material is more toxic than
either ethyl silicate or silicic acid, although it
has been thought that the injury caused is
largely due to the action of the silicic acid.
Flammable when exposed to heat or flame;
can react vigorously with oxidizing
materials. Potentially violent reaction with
metal hexafluorides (e.g., rhenium,
molybdenum, tungsten). When heated to
decomposition it emits acrid smoke and
irritating fumes.
Potential Exposure
Methyl silicate is used in coating
screens of television picture tubes. It may be used in mold
binders and in corrosion-resistant coatings; as well as in
catalyst preparation and as a silicone intermediate.
Shipping
UN2606 Methyl orthosilicate, Hazard class: 6.1;
Labels: 6.1-Poisonous materials, 3-Flammable liquid.
Purification Methods
Purification is as for tetraethoxysilane. It has a vapour pressure of 2.5mm at 0o. [IR: Sternbach & MacDiarmid J Am Chem Soc 81 5109 1959. Beilstein 1 IV 1266.]
Incompatibilities
Vapor may form explosive mixture with
air. Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep
away from alkaline materials, including alkaline earth
metals, metals, strong acids, strong bases; water, moisture,
steam decomposes releasing toxic, flammable gases.
Violent reaction with metal hexafluorides of rhenium,
molybdenum, and tungsten. Contact with metals may
evolve flammable hydrogen gas.
Check Digit Verification of cas no
The CAS Registry Mumber 681-84-5 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 6,8 and 1 respectively; the second part has 2 digits, 8 and 4 respectively.
Calculate Digit Verification of CAS Registry Number 681-84:
(5*6)+(4*8)+(3*1)+(2*8)+(1*4)=85
85 % 10 = 5
So 681-84-5 is a valid CAS Registry Number.
InChI:InChI=1/C2H6O3Si/c1-4-6(3)5-2/h1-2H3
681-84-5Relevant articles and documents
Direct Transformation of Silica into Alkoxysilanes by Gas-Solid Reactions
Suzuki, Eiichi,Akiyama, Masanari,Ono, Yoshio
, p. 136 - 137 (1992)
Silica gel is conveniently and efficiently converted into tetramethoxysilane by treatment with gaseous dimethyl carbonate at 500-600 K in the presence of an alkali hydroxide catalyst supported on the reacting silica.
The study of an alcoholysis reaction of silicon tetrafluoride with alcohols and magnesium to prepare tetraalkoxysilanes and magnesium fluoride
Zhang, Zongfan,Huang, Zhong,Tian, Qiang,Li, Yuye,Li, Xia,Liang, Xuesong,Du, Lusha
, p. 567 - 573 (2015)
An efficient alcoholysis reaction of silicon tetrafluoride with alcohols in the presence of magnesium can directly prepare tetraalkoxysilane and magnesium fluoride. The reaction can afford tetraethoxysilane, tetramethoxysilane, and magnesium fluoride in good yields with the aid of a catalytic amount of iodine.
-
Rochow
, p. 2170 (1948)
-
Mechanochemistry-a new powerful green approach to the direct synthesis of alkoxysilanes
Temnikov, Maxim N.,Anisimov, Anton A.,Zhemchugov, Pavel V.,Kholodkov, Dmitry N.,Goloveshkin, Alexander S.,Naumkin, Alexander V.,Chistovalov, Sergey M.,Katsoulis, Dimitris,Muzafarov, Aziz M.
, p. 1962 - 1969 (2018)
The present work shows a new one-stage mechanochemical method for the direct synthesis of alkoxysilanes by silicon mechanoactivation followed by a reaction with an alcohol. Alkoxysilanes were obtained with nearly complete silicon and alcohol conversion. This method allows for a considerable simplification of the traditional multistage process by eliminating three stages that include silicon and catalyst preparation, and adapts it to green chemistry requirements. Vibration milling removed the oxide film, and the mechanoactivation of the large silicon fraction (1000-2000 μm) occurs in the reactor working space. Abrasion of the reactor walls and grinding bodies made of brass results in a developed catalytic surface on silicon, as it has been proven by a set of physical analytical methods such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS).
Method for preparing organosilane by utilizing organosilicone byproduct
-
Paragraph 0024, (2020/07/13)
The invention relates to the technical field of production of organic silicon by-products. The invention aims to solve the problems of high cost, more three wastes and continuous production of byproducts in the traditional organic silicon byproduct treatment process. The method comprises the following steps: adding the organic silicon by-product into a nitrogen-protected glass lining reaction kettle with a tower, adding a catalyst, dropwise adding alcohol to the bottom of the glass lining reaction kettle, carrying out a heating reaction under a stirring condition, neutralizing the obtained material, and rectifying the neutralized material to obtain the organic silane. According to the method, the multi-component organic silicon by-products trichlorosilane and silicon tetrachloride react and are converted into the same product, the high-purity product can be obtained only through simple rectification and purification, the process is simple, the treatment cost is low, and the product hasgood economic value.
Direct transformation of silica from natural resources to form tetramethoxysilane
Putro, Wahyu S.,Fukaya, Keisuke,Choi, Jun-Chul,Choi, Seong Jib,Horikoshi, Toshio,Sato, Kazuhiko,Fukaya, Norihisa
, p. 958 - 962 (2020/09/04)
A simple and practical method for direct synthesis of tetramethoxysilane (TMOS) from silica (SiO2) and methanol was achieved using a base catalyst and acetal as a dehydrant under carbon dioxide (CO2). The production of TMOS was strongly influenced by the kind of the acetal used, with 2,2-dimeth-oxypropane identified as the most effective dehydrant. We observed that the acetal used enabled the production of a high yield of dimethyl carbonate (DMC), which promoted the TMOS production. DMC is an intermediate product from the reaction of CO2 and methanol, which supported the SiO2 depolymerization process. When the reaction is conducted with 2,2-dimethoxypropane at 260 °C for 24 h, TMOS can be produced in up to 59percent yield. For practical applications, the TMOS synthesis has been developed on a 250 mL and 1 L-scale reaction with constant yield (>50percent) from various silica resources.
