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Tetramethyl orthosilicate

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Tetramethyl orthosilicate Basic information
Tetramethyl orthosilicate Chemical Properties
  • Melting point:−4 °C(lit.)
  • Boiling point:121-122 °C(lit.)
  • Density 1.023 g/mL at 25 °C(lit.)
  • vapor density 5.25 (vs air)
  • vapor pressure 3.35 psi ( 20 °C)
  • refractive index n20/D 1.368(lit.)
  • Flash point:84 °F
  • storage temp. Flammables area
  • form liquid
  • color colorless
  • Specific Gravity1.032
  • explosive limit0.88-23.8%(V)
  • Water Solubility hydrolysis
  • Sensitive Moisture Sensitive
  • Hydrolytic Sensitivity7: reacts slowly with moisture/water
  • BRN 1699658
  • CAS DataBase Reference681-84-5(CAS DataBase Reference)
  • NIST Chemistry ReferenceTetramethyl silicate(681-84-5)
  • EPA Substance Registry SystemTetramethyl silicate (681-84-5)
Safety Information
Tetramethyl orthosilicate Usage And Synthesis
  • DescriptionSilicon esters are silicon compounds that contain an oxygen bridge from silicon to an organic group, for example, Si-OR. Tetramethoxysilane (TMOS), the methyl ester of orthosilicic acid, is a colorless, low-viscosity liquid. It is industrially the most important of the tetraalkyl silicates.

    • As an inorganic binder for refractory fillers and pigments, like precision investment castings;
    • As a second backup casting coating. It cures faster than colloidal silica system;
    • Hydrolyzed to form silicon dioxide (silica);
    • As a binder in zinc-rich (corrosion resistant) coating;
    • As a starting material for sol-gel process;
    • As a crosslinking agent for silicone sealant;
    • As a drying agent in sealing compositions;
    • As a chemical intermediate.
  • Chemical PropertiesMethyl silicate is a liquid.
  • Chemical PropertiesColorless transparent liquid
  • UsesUsed in the sol-gel synthesis of chromium-doped silicates1 and in the formation of hexagonal mesoporous silica layers.2
  • UsesCoating screens of television picture tubes; mold binders; corrosion-resistant coatings; catalyst preparation; silicone intermediate
  • Production MethodsSilica 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 DescriptionA 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 ReactionsFlammable. Insoluble in water.
  • Reactivity ProfileTetramethyl orthosilicate is incompatible with the following: Oxidizers; hexafluorides of rhenium, molybdenum & tungsten .
  • HazardEye damage and upper respiratory tract irri-tant.
  • Health HazardTOXIC; 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 HazardHIGHLY 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.
  • Safety ProfilePoison 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 ExposureMethyl 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.
  • ShippingUN2606 Methyl orthosilicate, Hazard class: 6.1; Labels: 6.1-Poisonous materials, 3-Flammable liquid.
  • Purification MethodsPurification 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.]
  • IncompatibilitiesVapor 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.
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