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Hexamethyldisiloxane Brief Description
Hexamethyldisiloxane (Hexamethyldisiloxane), also known as hexamethyldisiloxane, its chemical formula is $C_ {6} H_ {18} OSi_ {2} $, it is a colorless and transparent liquid at room temperature, with a special silicone odor.

1. ** Physical properties **
- The boiling point is low, about 101.5 ° C, which makes it vaporized under relatively mild conditions, easy to separate and volatilize in some processes.
- has a small density of 0.765 g/mL (25 ° C), is lighter than water, and has a unique behavior in some systems involving liquid-liquid separation.
- has good solubility and can be miscible with a variety of organic solvents such as ether, benzene, acetone, etc., but is insoluble in water. This solubility characteristic makes it widely used in the fields of organic synthesis and material preparation.
2. ** Chemical properties **
- has a certain chemical stability, the silicon-oxygen bond is relatively stable, and it is not easy to break under general conditions. However, under specific conditions such as strong acid, strong base or high temperature, its silicon-oxygen bond can undergo reactions such as hydrolysis or alcoholysis. For example, under strong acid catalysis, hydrolysis can occur with water to generate products such as silanol.

II. Production
1. ** Direct method **
Using silicon powder and chloromethane as raw materials, in the presence of copper catalyst, the reaction is carried out at about 300 ° C to generate a mixed monomer of methylchlorosilane, and then the dimethyl dichlorosilane is separated by rectifying. The latter undergoes hydrolysis or alcoholysis under the action of water or alcohol, and the generated dimethyl silanediol is dehydrated and condensed to obtain hexamethyldisiloxane. The raw material of this method is easy to obtain and suitable for large-scale industrial production, but the reaction conditions are more harsh and the equipment requirements are higher.
2. ** Indirect method **
is prepared by hydrolysis of trimethylchlorosilane. Trimethylchlorosilane reacts with water under certain conditions, and chlorine atoms are replaced by hydroxyl groups to form trimethylsilanol. The dehydration and condensation reaction between trimethylsilanol occurs to obtain hexamethyldisiloxane. The reaction of this method is relatively mild, but the cost of raw material trimethylchlorosilane is relatively high, which limits its large-scale application.

III. Application
1. ** Field of silicone synthesis **
- As a head agent, it is widely used in the synthesis of silicone polymers such as silicone oil and silicone rubber. In the polymerization process of silicone polymers, the addition of hexamethyldisiloxane can control the molecular weight and chain structure of the polymer, so that it can meet the requirements of different application scenarios for material properties. For example, when synthesizing linear silicone oil, it can be terminated to prevent further growth of the polymer chain, so as to obtain a silicone oil product with a specific viscosity.
2. ** Cosmetics industry **
Because of its good volatility and spreadability, it is often added to cosmetics. In skin care products, it is able to give the product a refreshing and non-greasy feel of use, while contributing to the uniform distribution and penetration of active ingredients. In makeup products such as loose powder and powder, it can improve the fluidity of the powder, making it easier to apply makeup and longer lasting makeup effect.
3. ** Electronics Industry **
- In the semiconductor manufacturing process, it can be used as a cleaning agent. Due to its good dissolution and cleaning ability to some organic pollutants and metal impurities, and good volatility, it will not leave residues, which can effectively clean the surface of semiconductor materials such as silicon wafers and improve the yield of chip manufacturing. In addition, in electronic packaging materials, it can also be used to improve the flexibility and weather resistance of materials.