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.
Reactivity Profile
METHYL ORTHOSILICATE(681-84-5) is incompatible with the following: Oxidizers; hexafluorides of rhenium, molybdenum & tungsten .
Air & Water Reactions
Flammable. Insoluble in water.
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.
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.
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.
First aid
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical contacts the
skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from exposure,
begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if
heart action has stopped. Transfer promptly to a medical
facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce
vomiting. Do not make an unconscious person vomit.
Medical observation is recommended for 24 to 48 hours
after breathing overexposure, as pulmonary edema may be
delayed. As first aid for pulmonary edema, a doctor or
authorized paramedic may consider administering a drug
or other inhalation therapy.
Shipping
UN2606 Methyl orthosilicate, Hazard class: 6.1;
Labels: 6.1-Poisonous materials, 3-Flammable liquid.
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.
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
Colorless transparent liquid
Chemical Properties
Methyl silicate is a liquid.
Uses
Coating screens of television picture
tubes; mold binders; corrosion-resistant coatings;
catalyst preparation; silicone intermediate
Uses
Used in the sol-gel synthesis of chromium-doped silicates1 and in the formation of hexagonal mesoporous silica layers.2
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.
Flammability and Explosibility
Flammable
storage
Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Prior to working with thischemical you should be trained on its proper handling andstorage. Store in tightly closed containers in a cool, wellventilated area away from water and moisture. Sources ofignition, such as smoking and open flames, are prohibitedwhere methyl silicate is used, handled, or stored in a manner that could create a potential fire or explosion hazard.
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.]
