Trimethylsilyl chloride

Trimethylsilyl chloride, also known by its systematic name chlorotrimethylsilane (CTMS), is a chemical compound with the formula (CH₃)₃SiCl. This organosilicon compound is a colorless, volatile liquid that is used in various chemical synthesis and industrial applications, primarily as a silylating agent to introduce trimethylsilyl (TMS) protective groups.

Properties

Trimethylsilyl chloride is characterized by its ability to react with a wide range of nucleophiles, including alcohols, amines, and carboxylic acids, to form trimethylsilyl ethers, amines, and esters, respectively. These reactions typically require the presence of a base, such as triethylamine, to neutralize the hydrochloric acid by-product.

Physical Properties

• Molecular Weight: 108.64 g/mol
• Boiling Point: 57-58°C at 760 mmHg
• Density: 0.856 g/mL at 25°C

Chemical Properties

Trimethylsilyl chloride is highly reactive towards nucleophiles due to the presence of the silicon-chlorine bond, which is polarized, making the silicon atom electrophilic. This reactivity is exploited in organic synthesis, particularly in the protection of hydroxyl groups.

Applications

The primary use of trimethylsilyl chloride is in the field of organic synthesis, where it serves as a silylating agent to protect hydroxyl groups in alcohols and phenols, as well as carboxylic acids and amines. This protection strategy is crucial in multi-step synthetic routes where selective reactions are required.

In Organic Synthesis

• Protection of Alcohols and Phenols: Alcohols and phenols can be converted to their trimethylsilyl ethers, which are resistant to a variety of reaction conditions. Upon completion of the synthetic sequence, the protecting group can be removed to regenerate the alcohol or phenol.
• Protection of Carboxylic Acids and Amines: Similar to alcohols, carboxylic acids and amines can be protected as trimethylsilyl esters and amines, respectively.

Industrial Applications

Beyond organic synthesis, trimethylsilyl chloride finds applications in the production of silicone polymers and as an intermediate in the manufacture of other organosilicon compounds.

Safety and Handling

Trimethylsilyl chloride is corrosive and should be handled with care. It reacts violently with water, releasing hydrochloric acid, and requires storage in a cool, dry place, away from moisture. Appropriate personal protective equipment (PPE) should be worn when handling this chemical.

See Also

• Organosilicon chemistry
• Protecting group
• Silylation
• Silicone polymers