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Send EmailTetramethyl Orthosilicate, Tetramethoxysilane, Methyl Silicate, Silicon Methoxide, TMOS, 681-84-5
| Parameter | Information |
|---|---|
| Chemical Name (IUPAC) | Tetramethyl Orthosilicate |
| Other Names | Tetramethoxysilane, Methyl Silicate, Silicon Methoxide, Silicic Acid Tetramethyl Ester, TMOS |
| Chemical Formula | Si(OCH₃)₄ |
| Molecular Weight | 152.25 g/mol |
| CAS Number | 681-84-5 |
| EC Number (EINECS) | 211-656-4 |
| MDL Number | MFCD00008341 |
| SMILES String | COSi(OC)OC |
| Appearance | Colorless, clear liquid |
| Chemical Class | Organosilicon compound (alkoxide) |
Tetramethyl Orthosilicate (TMOS) is an organosilicon compound with the formula Si(OCH₃)₄. It is the methyl ester of orthosilicic acid and is considered the most industrially significant among the tetraalkyl silicates . It is a colorless liquid with low viscosity, characterized by its excellent hydrolyzing and polymerizing properties, making it highly valuable in various chemical and material synthesis processes . It is insoluble in water .
TMOS consists of four methyl groups attached to the hypothetical anion SiO₄⁴⁻. The basic properties are similar to the more popular TEOS (Tetraethyl Orthosilicate), which is usually preferred because its hydrolysis product, ethanol, is less toxic than methanol .
| Property | Value |
|---|---|
| Appearance | Colorless, clear liquid |
| Molecular Formula | Si(OCH₃)₄ |
| Molecular Weight | 152.25 g/mol |
| Density (20°C) | 1.03 g/cm³ |
| Density (25°C) | 1.023 g/mL |
| Melting Point | -4 °C to 5 °C (depending on purity) |
| Boiling Point | 121 – 122 °C |
| Flash Point | 26 °C (closed cup) |
| Autoignition Temperature | 245 °C |
| Vapor Pressure (20°C) | 13 hPa |
| Vapor Pressure (25°C) | 18 hPa |
| Vapor Density | 5.25 (vs air) |
| Refractive Index (20°C) | 1.368 |
| Explosive Limit | 0.88 – 23.8 % (v/v) |
| Reaction with Water | Rapid hydrolysis (forms methanol and SiO₂) |
| Hydrolytic Sensitivity | Highly sensitive to moisture |
Structure:
OCH₃
|
H₃CO — Si — OCH₃
|
OCH₃
SMILES: COSi(OC)OC
Hydrolysis Reaction:
TMOS rapidly hydrolyzes in the presence of water to form silica (SiO₂) and methanol :
Si(OCH₃)₄ + 4H₂O → Si(OH)₄ + 4CH₃OH
Condensation Reaction:
Si(OH)₄ → SiO₂ + 2H₂O
Overall Reaction:
Si(OCH₃)₄ + 2H₂O → SiO₂ + 4CH₃OH
Organic Synthesis Application:
In organic synthesis, Si(OCH₃)₄ has been used to convert ketones and aldehydes to the corresponding ketals and acetals, respectively .
TMOS is used primarily as a silica source in various chemical and material synthesis processes .
| Application | Description |
|---|---|
| Silica Production | Used in the sol-gel synthesis of chromium-doped silicates and in the formation of hexagonal mesoporous silica layers |
| Perovskite Nanocrystals | Used in the synthesis of water-stable CsPbBr₃@SiO₂ perovskite nanocrystals, forming a protective siloxane network that enhances their stability for bioimaging applications |
| Quantum Dots | Used to form a protective SiO₂ matrix around CsPbBr₃ quantum dots, enabling self-enhanced electrochemiluminescence for advanced optoelectronic applications |
| Magnetic Nanoparticles | Used in the surface modification of magnetic nanoparticles to form a silica coating, enhancing their surface area and enabling efficient drug loading for targeted delivery applications |
| Application | Description |
|---|---|
| Optical Coatings | Anti-reflective and protective optical coatings |
| Insulation Layers | Insulating layers in electronic and optical applications |
| Surface Modification | Surface property modification and water repellency |
| Application | Description |
|---|---|
| Semiconductors | Dielectric coatings and insulation layers |
| MEMS | Micro-electromechanical systems |
| Optical Glass | Specialty optical glass formulations |
| Application | Description |
|---|---|
| Ketals and Acetals | Conversion of ketones and aldehydes to corresponding ketals and acetals |
| Property | TMOS | TEOS |
|---|---|---|
| Formula | Si(OCH₃)₄ | Si(OC₂H₅)₄ |
| Molecular Weight | 152.25 g/mol | 208.33 g/mol |
| Boiling Point | 121-122 °C | 168 °C |
| Flash Point | 26 °C | 45 °C |
| Hydrolysis Rate | Faster | Slower |
| Hydrolysis Product | Methanol (highly toxic) | Ethanol (less toxic) |
| Volatility | Higher | Lower |
| Preferred Use | Faster reactions | Safer handling |
Why TEOS is Often Preferred: TEOS is usually preferred because the product of hydrolysis, ethanol, is less toxic than methanol. Additionally, TEOS is considerably less volatile and is hydrolyzed more slowly by water in the lungs and on the eyes (due to steric bulk), making it safer for handling .
| Grade | Purity | Application |
|---|---|---|
| Standard Grade | ≥98.0% | General applications |
| Deposition Grade | ≥98%, ≥99.9% trace metals basis | Semiconductor and deposition applications |
| Purum Grade | ≥98.0% (GC) | High-purity applications |
WARNING: TMOS is a highly hazardous substance!
| Parameter | Value |
|---|---|
| Signal Word | Danger |
| Oral LD50 (Rat) | > 2,500 mg/kg |
| Dermal LD50 (Rabbit) | 17,510 mg/kg |
| Inhalation LC50 (Rat, 4h) | 0.39 mg/L (vapor) |
| Hazard Category | Description |
|---|---|
| Acute Toxicity | Category 1 (H330) - Fatal if inhaled |
| Eye Damage | Category 1 (H318) - Causes serious eye damage |
| Flammable Liquids | Category 3 (H226) - Flammable liquid and vapor |
| Skin Irritation | Category 2 (H315) - Causes skin irritation |
Hazard Statements:
H226: Flammable liquid and vapor
H315: Causes skin irritation
H318: Causes serious eye damage
H330: Fatal if inhaled
TOXICITY MECHANISM:
The hydrolysis of Si(OCH₃)₄ produces insoluble SiO₂ and CH₃OH (methanol). Even at low concentrations, inhalation causes lung lesions; at slightly higher concentrations, eye contact with the vapor causes blindness. Worse, at low concentrations (200 ppm/15 min), the damage is often insidious, with onset of symptoms hours after exposure. The mode of action is the precipitation of silica in the eyes and/or lungs .
METHANOL NOTE: Contrary to common information, the methanol produced is relatively innocuous compared to the silica precipitation mechanism. Methanol causes blindness via conversion to formaldehyde in the liver, but methanol splashes to the eye cause only moderate and reversible eye irritation. The primary mechanism of toxicity is silica precipitation in tissues .
| Equipment | Requirement |
|---|---|
| Respiratory Protection | Type ABEK (EN14387) respirator filter |
| Hand Protection | Gloves |
| Eye Protection | Eyeshields, Faceshields |
| Storage Class | 3 - Flammable liquids |
| WGK | 1 (slightly water hazardous) |
| Route of Exposure | Action |
|---|---|
| Inhalation | Remove to fresh air. Fatal if inhaled. Seek immediate medical attention. |
| Skin Contact | Wash with plenty of soap and water. Remove contaminated clothing. |
| Eye Contact | Rinse thoroughly with water for at least 15 minutes. Causes serious eye damage. Seek immediate medical attention. |
| Ingestion | Do NOT induce vomiting. Rinse mouth. Seek immediate medical attention. |
| Parameter | Information |
|---|---|
| Storage Conditions | Cool, dry, well-ventilated area |
| Storage Temperature | 2-30°C |
| Container Requirements | Tightly closed, protected from moisture |
| Protect From | Moisture, water, heat, sparks, flames |
| Shelf Life | 12 months (under proper conditions) |
| Packaging | Metal or HDPE drums, glass bottles |
| Special Note | Due to its specific melting range, the product may be solid, liquid, a solidified melt, or a supercooled melt |
| Parameter | Information |
|---|---|
| UN Number | 2606 |
| Hazard Class | 3 (Flammable Liquid) + 6.1 (Toxic) |
| Packing Group | I |
| Region / Authority | Status |
|---|---|
| European Union (REACH) | Registered substance |
| USA (EPA TSCA) | Listed on TSCA inventory |
| USA (NIOSH) | REL: TWA 1 ppm (6 mg/m³) |
| Type | Name |
|---|---|
| Turkish Names | Tetrametil Ortosilikat, Tetrametoksisilan, Metil Silikat |
| English Names | Tetramethyl Orthosilicate, Tetramethoxysilane, Methyl Silicate, Silicon Methoxide |
| Abbreviation | TMOS |
| CAS Number | 681-84-5 |
| Parameter | Value |
|---|---|
| Product | Tetramethyl Orthosilicate (TMOS) |
| CAS Number | 681-84-5 |
| Formula | Si(OCH₃)₄ |
| Molecular Weight | 152.25 g/mol |
| Appearance | Colorless, clear liquid |
| Boiling Point | 121-122 °C |
| Flash Point | 26 °C |
| Primary Applications | Sol-gel, nanoparticles, thin films, coatings, organic synthesis |
1. HIGH TOXICITY: TMOS is fatal if inhaled (Acute Tox. 1). Even at low concentrations, inhalation causes lung lesions . Proper respiratory protection is mandatory during handling.
2. SERIOUS EYE DAMAGE: Causes serious eye damage (Eye Dam. 1). Eye contact with vapor can cause blindness. The mechanism is precipitation of silica in the eyes .
3. INSIDIOUS TOXICITY: At low concentrations (200 ppm/15 min), damage is often insidious, with onset of symptoms hours after exposure .
4. METHANOL RELEASE: Hydrolysis releases methanol. While methanol toxicity is known, the primary mechanism of TMOS toxicity is silica precipitation in tissues .
5. MOISTURE SENSITIVITY: Highly sensitive to moisture and hydrolyzes rapidly. Must be stored in tightly sealed containers away from moisture.
6. FLAMMABILITY: Flammable liquid with a flash point of 26°C. Keep away from heat, sparks, and open flames.
7. PPE: Use protective gloves, safety goggles, faceshields, and Type ABEK respirator filter when handling .
8. TMOS vs TEOS: TEOS is often preferred because ethanol (hydrolysis product) is less toxic than methanol, and TEOS is less volatile and hydrolyzes more slowly .
9. TRANSPORT: UN 2606, Class 3 (Flammable) + 6.1 (Toxic). Packing Group I.
10. STORAGE: Store in a cool, dry, well-ventilated area at 2-30°C in original containers. Keep absolutely protected from moisture.
IMPORTANT DISCLAIMER: This Technical Data Sheet (TDS) is for informational purposes only and is prepared based on available technical data. The user is responsible for determining the suitability of the product for their specific application and for complying with all local, national, and international regulations. For complete safety, storage, use, handling, disposal, and regulatory compliance information, refer to the official Safety Data Sheet (SDS/MSDS) provided by the manufacturer/supplier. This document is not a substitute for professional or medical advice.