Jiangxi Huahao Chemical Knowledge – Hexamethyldisiloxane

　　Hexamethyl disiloxane (silicone ether, MM capping agent) is a colorless, transparent liquid that is hygroscopic. It is insoluble in water but readily dissolves in a variety of organic solvents. This compound is widely used as a raw material for silicone oils, silicone rubber, pharmaceuticals, gas chromatography stationary phases, analytical reagents, and hydrophobic coatings. It is produced by the hydrolysis of trimethylchlorosilane.
　　Introduction
　　Chinese aliases: Hexamethyldisiloxane; Hexamethyldioxysilane; Siloxane
　　English aliases: HMDSO; Hexamethyl Disiloxane; MM
　　Physicochemical Properties
　　1. Characteristics: Colorless, transparent liquid; highly hygroscopic.
　　2. Solubility: Insoluble in water, soluble in most organic solvents;
　　Stability: Stable;
　　Hazard label: F - Flammable substance
　　3. Technical Specifications:
　　Density: 0.762–0.770 g/mL
　　Refractive index: 1.3748
　　Melting point: -59°C
　　Boiling point: 99.5°C
　　Flash point: -1°C
　　4. Hazardous Properties: Easily ignited by high heat, open flames, and strong oxidizing agents.
　　Combustion (decomposition) products: carbon monoxide, carbon dioxide, silicon oxide.
　　Synthesis method
　　Add 62.49 g (0.575 mol) of trimethylchlorosilane dropwise to a solution containing 72.7 g (0.06 mol) of N,N-dimethylaniline and 7 g of water, then heat the mixture under reflux for 1 hour. Perform distillation at atmospheric pressure, collecting the fraction between 98–101°C. After drying, the product is hexamethyldisiloxane, yielding 43–44 g with a 92–94% overall yield. In industrial production, trimethylchlorosilane is hydrolyzed in water at 30–40°C. [2]
　　Main uses
　　Used in applications such as silicone oil, silicone rubber, pharmaceuticals, stationary phase for gas chromatography, analytical reagents, and hydrophobic agents. This product serves as a sealing agent, cleaning agent, and mold-release agent, primarily utilized in organic chemical and pharmaceutical chemical manufacturing processes.