Hexamethyldisiloxane
[CAS# 107-46-0]

Identification

• Classification: Organic raw materials >> Organosilicon compound
• Name: Hexamethyldisiloxane
• Synonyms: HMDSO
• Molecular Formula: C₆H₁₈OSi₂
• Molecular Weight: 162.38
• CAS Registry Number: 107-46-0
• EC Number: 203-492-7
• SMILES: C[Si](C)(C)O[Si](C)(C)C

Properties

• Water solubility: insoluble
• Density: 0.8±0.1 g/cm³, Calc.^*, Density|0.764 g/mL (Expl.)
• Melting point: -59 ºC (Expl.)
• Index of Refraction: 1.393, Calc.^*, 1.377 (Expl.)
• Boiling Point: 100.9±8.0 ºC (760 mmHg), Calc.^*, 101 ºC (Expl.)
• Flash Point: 7.7±18.8 ºC, Calc.^*, -1 ºC (Expl.)

Safety Data

• Hazard Symbols: GHS02;GHS09 Danger
• Hazard Statements: H225-H400-H410-H411
• Precautionary Statements: P210-P233-P240-P241-P242-P243-P273-P280-P303+P361+P353-P370+P378-P391-P403+P235-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Flammable liquids	Flam. Liq.	2	H225
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Carcinogenicity	Carc.	2	H351
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Flammable liquids	Flam. Liq.	3	H226
Specific target organ toxicity - single exposure	STOT SE	3	H336
Substances or mixtures which in contact with water emit flammable gases	Water-react.	1	H260
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Aspiration hazard	Asp. Tox.	1	H304
Flammable solids	Flam. Sol.	1	H228

• Transport Information: UN 1993

Discovory and Applicatios

Hexamethyldisiloxane is a widely used organosilicon compound known for its unique chemical structure and versatility. It is composed of two silicon atoms linked by an oxygen atom, with each silicon atom bonded to three methyl groups. This structure gives hexamethyldisiloxane its distinct chemical and physical properties, including low viscosity, high volatility, and excellent thermal stability. These properties make it useful across a variety of industrial and commercial applications.

The compound was first synthesized in the mid-20th century as part of the broader development of organosilicon chemistry. Scientists sought to explore the utility of silicon-containing compounds due to their stable chemical bonds and resistance to degradation. Hexamethyldisiloxane became a key example of how such compounds could be used in various applications, ranging from coatings and lubricants to personal care products and medical formulations. The synthesis of hexamethyldisiloxane is typically carried out by reacting chlorosilanes with appropriate nucleophiles, such as alkoxides or organomagnesium reagents. One of the most common methods involves the reaction of trimethylchlorosilane with magnesium to form the corresponding organomagnesium intermediate, which is then treated with water or an alcohol to form hexamethyldisiloxane.

As a solvent, hexamethyldisiloxane is widely utilized in many industries, especially those requiring low viscosity and high volatility. Its ability to dissolve a wide range of materials, both polar and non-polar, makes it a valuable solvent in the preparation of coatings, paints, and cleaning agents. The compound is also used as a lubricant and fluid carrier in high-temperature environments due to its excellent chemical stability and ability to remain liquid at elevated temperatures. Its volatility and low surface tension make it especially effective in formulations designed to spread evenly and dry quickly.

In addition to its role as a solvent, hexamethyldisiloxane is crucial in the production of silicones, which are used to make products like silicone oils, rubber, and resins. These materials are valued for their unique properties, including heat resistance, water repellency, and electrical insulation. Hexamethyldisiloxane serves as a precursor in the synthesis of more complex siloxane compounds, enabling the production of materials with tailored properties. The versatility of these materials has led to their use in a wide range of industries, from automotive to electronics, where they are used for everything from insulation to adhesives.

Hexamethyldisiloxane is also employed in the personal care industry, where it is used in shampoos, conditioners, and other cosmetic products. Its ability to provide a smooth, non-greasy feel while improving the texture and spreadability of products makes it a popular ingredient in many formulations. It is often used in hair care products for its conditioning properties and to reduce frizz, leaving hair soft and manageable. Similarly, in cosmetics, it helps products glide on easily and gives skin a silky finish.

The compound is also found in certain medical products, particularly in topical ointments and skin treatments. Its non-irritating nature and ability to form a moisture barrier make it useful in formulations designed to protect the skin or aid in healing. Its use in such applications underscores its versatility and the broad range of properties that make it valuable across various industries.

Hexamethyldisiloxane continues to play a significant role in the development of new materials and products, particularly in fields requiring high-performance liquids, coatings, and adhesives. Its wide range of applications, from industrial uses to personal care products, ensures its continued relevance in both commercial and scientific contexts.

References

2005. A Synthetic Cycle for H2/CO Activation and Allene Synthesis Using Recyclable Zirconium Complexes. Journal of the American Chemical Society.
DOI: 10.1021/ja0567079

2003. Closed-Chamber Inhalation Pharmacokinetic Studies with Hexamethyldisiloxane in the Rat. Inhalation Toxicology.
DOI: 10.1080/08958370390205083

2001. Potential Estrogenic and Antiestrogenic Activity of the Cyclic Siloxane Octamethylcyclotetrasiloxane (D4) and the Linear Siloxane Hexamethyldisiloxane (HMDS) in Immature Rats Using the Uterotrophic Assay. Toxicological Sciences: An Official Journal of the Society of Toxicology.
DOI: 10.1093/toxsci/63.1.37