Hexamethyldisiloxane

Chemical properties

Hexamethyldisiloxane (HMDS) is a colorless or yellowish transparent liquid with a measured melting point of -68.2°C and a measured boiling point of 100.5°C at 1013 hPa. The measured vapor pressure is 44.51 hPa at 20 oC. The measured water solubility is 0.93 ± 0.63 mg/L at 23 oC. The measured log Kow of HMDS is 5.20 at 20 oC. Estimated log Koc values using EPISuite v 4.10 range from 2.5 (MCI method) to 4.5 (Kow method). As Episuite does not contain fragments for siloxanes for log Koc predictions, these values should be treated with caution. The potential for hydrolysis of the test substance may have influenced the determination of partition coefficient and water solubility.

Physical properties

Hexamethyldisiloxane is a colorless and transparent liquid. It is easily deliquescent, flammable, and has the risk of causing combustion when exposed to high heat, open flame, and strong oxidizing agents. Boiling point 99.5℃. Flash point -1.1℃. Relative density (d2525) 0.7606. refractive index 1.3750. insoluble in water, soluble in many organic solvents.

The Uses of Hexamethyldisiloxane

Hexamethyldisiloxane is used as a base fluid in a wide range of personal care products that require fast evaporation and high spreadability. When blended with Dimethicone fluids, It can adjust the residence time of the silicone on the skin. Unlike other volatile fluids, Hexamethyldisiloxane Fluid does not cool the skin as it evaporates. Hexamethyldisiloxane is used as a carrying agent and diluent in the following: skin cream lotions, bath oils, suntan lotions, nail polishes, antiperspirants, deodorants, hair sprays and other beauty and hair care products.
A silicon based compound that can be used to create potentially biocompatible materials.
Used as a monomer in the synthesis of long chain polysiloxane structures.
Used in the methylation of mercury(II) salts.

The Uses of Hexamethyldisiloxane

The most popular precursor chemical is hexamethyldisiloxane (HMDS) which with the addition of helium and oxygen will produce a silica coating. it is used in a variety of consumer applications and can be used as intermediates in the production of silicone polymers.

The Uses of Hexamethyldisiloxane

Hexamethyldisiloxane can be used as silylating agent for carboxylic acids, and alcohols; used in preparation of aroyl chlorides; precursor for a variety of trimethylsilyl derivatives.Hexamethyldisiloxane has been used as an inexpensive starting material for the preparation of numerous synthetically useful trimethylsilyl derivatives.

Definition

ChEBI: Hexamethyldisiloxane is an organosiloxane consisting of two trimethylsilyl groups covalently bound to a central oxygen.

Production Methods

Produced via acid hydrolysis of chlorotrimethylsilane and purification by distillation.

Preparation

Synthesis of hexamethyldisiloxane by hydrolysis of trimethylsilyl chloride, water and sodium hydroxide.

General Description

Hexamethyldisiloxane (HMDSO), a linear polydisiloxane, is an organosilicon reagent commonly utilized as a source for plasma enhanced chemical vapor deposition (PE-CVD) of thin films of silicon compounds. It is also employed as a substitute to silane in silicon integrated circuit technology. Its dissociative ionization by electron impact has been studied by Fourier transform mass spectrometry. Synthesis of plasma-polymerized HMDSO thin films by atmospheric pressure glow (APG) discharge has been reported. Crystals of HMDSO at 148K are monoclinic. Addition of HMDSO to P₄S₁₀, improves its efficiency as thionating agent.

Flammability and Explosibility

Highly flammable

Purification Methods

Fractionally distil through a column packed with glass helices with ca 15 theoretical 20 1.3777. plates. It is highly flammable and is an irritant. [Mills & McKenzie J Am Chem Soc 76 2672 1954, Csakvari et al. J Organometal Chem 107 287 1976, Beilstein 4 IV 4018.]