What Chemical Is CAS Number 1066-35-9?
The CAS number 1066-35-9 is assigned to chlorodimethylsilane, a chemical also known as dimethylchlorosilane or DMCS. Its molecular formula is C2H7ClSi and its molecular weight is approximately 92.62. Chlorodimethylsilane is a colorless, transparent liquid that belongs to the chlorosilane family of organosilicon compounds. Because it carries both a silicon-hydrogen bond and a silicon-chlorine bond, it is a highly reactive building block used to introduce dimethylsilyl groups into other molecules. It reacts readily with moisture in the air, releasing hydrogen chloride, and must therefore be handled and stored under dry conditions.
Key Properties of Chlorodimethylsilane
The table below lists the main properties of chlorodimethylsilane (DMCS) for industrial reference.
| Property | Value |
|---|---|
| Chemical name | Chlorodimethylsilane (dimethylchlorosilane) |
| CAS number | 1066-35-9 |
| Molecular formula | C2H7ClSi |
| Molecular weight | Approximately 92.62 |
| Appearance | Colorless transparent liquid |
| Boiling point | Approximately 35 C |
| Flash point | Approximately -9 C (closed cup) |
| Reactivity | Hydrolyzes in moist air, releasing hydrogen chloride; reacts with water and alcohols |
| Typical packaging | 10 kg plastic drum, under dry inert conditions |
Commercial grades typically offer an assay of 99% minimum by gas chromatography. Due to its low boiling point and flammability, chlorodimethylsilane must be kept away from ignition sources and moisture.
Intermediate for Organosilicon Compounds
The most important application of chlorodimethylsilane is as an intermediate in organosilicon chemistry:
It is used to synthesize a wide range of organosilicon compounds, including silane coupling agents, silicone oils and silicone resins.
It is a key precursor in the preparation of hydrosilanes such as trimethylsilane, which are used in hydrosilylation reactions.
The silicon-hydrogen bond it carries enables further functionalization, making it a versatile starting material for specialty silicone products.
This role places DMCS among the basic raw materials of the silicone industry.
Surface Treatment and Silanization
Chlorodimethylsilane is widely used to modify the surface properties of inorganic materials:
Surface treatment of glass, metals, ceramics and nanoparticles to impart hydrophobic or other functional characteristics.
Improvement of adhesion and compatibility between fillers and polymer matrices in composite materials.
Deactivation of glass surfaces and chromatographic supports, where silanization reduces unwanted surface activity and improves analytical reproducibility.
In these applications, the chlorosilane reacts with surface hydroxyl groups to form stable silicon-oxygen bonds, permanently changing the surface chemistry.
Pharmaceutical and Fine Chemical Applications
In the pharmaceutical and fine chemical industries, chlorodimethylsilane serves as a specialized reagent:
It introduces protective silyl groups, for example protecting hydroxyl or amino functional groups during multi-step organic synthesis.
It can be used as an intermediate in the production of silicon-containing pharmaceutical compounds.
Its high selectivity and reactivity make it useful in small-scale and pilot-scale synthesis where controlled silylation is required.
These applications require high-purity material and careful moisture control to achieve reproducible results.
Safe Handling and Storage
Chlorodimethylsilane is a moisture-sensitive, corrosive and flammable liquid. The following precautions are essential:
Store in tightly sealed containers under a dry, inert atmosphere such as nitrogen.
Keep away from water, moisture, oxidizers and ignition sources; the flash point is approximately -9 C.
Use the material under a fume hood or with local exhaust ventilation, because hydrolysis releases hydrogen chloride vapor.
Wear chemical-resistant gloves, safety goggles and protective clothing; avoid skin and eye contact.
In case of leakage, do not use water; contain the spill with dry sand or inert absorbent and dispose of it according to local regulations.
Correct handling prevents hazardous reactions and protects personnel from corrosive exposure.
Frequently Asked Questions
What is the chemical at CAS number 1066-35-9?
CAS 1066-35-9 identifies chlorodimethylsilane, also known as dimethylchlorosilane or DMCS, with the molecular formula C2H7ClSi.
What is the boiling point of chlorodimethylsilane?
The boiling point of chlorodimethylsilane is approximately 35 C, which makes it a highly volatile liquid. It must be handled and stored with vapor control in mind.
Is chlorodimethylsilane water reactive?
Yes. Chlorodimethylsilane hydrolyzes in contact with water or moisture, releasing hydrogen chloride gas. It must be kept dry and handled under inert conditions.
What is DMCS used for?
DMCS is used as an intermediate for organosilicon compounds, as a surface treatment agent for silanization of glass, metals, ceramics and nanoparticles, and as a reagent for introducing protective silyl groups in pharmaceutical and fine chemical synthesis.
What is the molecular formula of chlorodimethylsilane?
The molecular formula is C2H7ClSi, with a molecular weight of approximately 92.62.
How should chlorodimethylsilane be stored?
Store it in tightly sealed containers under a dry inert atmosphere, away from moisture, oxidizers and ignition sources. Use dry absorbents for spill control and never use water.
