Hexamethyldisilazane
[CAS# 999-97-3]

Identification

• Classification: Organic raw materials >> Organosilicon compound
• Name: Hexamethyldisilazane
• Synonyms: 1,1,1,3,3,3-Hexamethyldisilazane; 1,1,1-Trimethyl-N-(trimethylsilyl)silanamine; Hexamethyl disilizane; HMDS
• Molecular Formula: C₆H₁₉NSi₂
• Molecular Weight: 161.39
• CAS Registry Number: 999-97-3
• EC Number: 213-668-5
• SMILES: C[Si](C)(C)N[Si](C)(C)C

Properties

• Water solubility: React
• Density: 0.765 g/mL (Expl.)
• Melting point: -78 ºC (Expl.)
• Boiling point: 125 ºC (Expl.)
• Refractive index: 1.407 (Expl.)
• Flash point: 20 ºC (Expl.)

Safety Data

• Hazard Symbols: GHS02;GHS05;GHS06;GHS07 Danger
• Hazard Statements: H225-H302+H332-H302-H311-H314-H332-H412
• Precautionary Statements: P210-P233-P240-P241-P242-P243-P260-P261-P262-P264-P270-P271-P273-P280-P301+P317-P301+P330+P331-P302+P352-P302+P361+P354-P303+P361+P353-P304+P340-P305+P354+P338-P316-P317-P321-P330-P361+P364-P363-P370+P378-P403+P235-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	3	H311
Flammable liquids	Flam. Liq.	2	H225
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Skin corrosion	Skin Corr.	1B	H314
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	3	H331
Serious eye damage	Eye Dam.	1	H318
Specific target organ toxicity - single exposure	STOT SE	3	H335
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Eye irritation	Eye Irrit.	2A	H319
Acute toxicity	Acute Tox.	3	H301
Pyrophoric liquids	Pyr. Liq.	1	H250
Skin corrosion	Skin Corr.	1	H314
Specific target organ toxicity - single exposure	STOT SE	1	H370

Discovory and Applicatios

Hexamethyldisilazane is an organosilicon compound with significant utility across various industries. Composed of two methyl groups attached to a central silicon atom, hexamethyldisilazane (HMDS) is primarily known for its use as a silylating agent, providing a pathway for modifying surface properties and enhancing chemical reactivity. Its structure, consisting of a silicon-nitrogen bond, makes it highly reactive, allowing it to form stable bonds with a variety of substrates, especially those with hydroxyl groups, such as glass, metal oxides, and ceramics.

The discovery of hexamethyldisilazane can be traced back to the increasing interest in organosilicon compounds during the mid-20th century. The ability of silanes to react with hydroxyl groups and form siloxane bonds positioned HMDS as a versatile compound with broad industrial applications. The synthesis of hexamethyldisilazane typically involves the reaction of chlorosilanes with ammonia or amines, which allows for the incorporation of the methyl groups into the silicon framework. This process results in a compound with unique chemical properties, such as its low volatility, excellent thermal stability, and ability to act as a precursor for various silane-based materials.

One of the most important applications of hexamethyldisilazane is in surface modification. Due to its ability to bond to siliceous surfaces, it is widely used in the preparation of hydrophobic coatings for glass, ceramics, and metals. These coatings provide resistance to moisture, oxidation, and corrosion, making HMDS a key component in the production of protective coatings for electronics, optics, and automotive parts. The compound's ability to impart non-stick properties to surfaces also makes it valuable in the manufacturing of consumer goods such as cookware and textiles, where water or oil repellency is a desirable feature.

In addition to surface modification, hexamethyldisilazane plays a crucial role in the semiconductor industry. It is commonly used in the fabrication of integrated circuits and microelectromechanical systems (MEMS), where it serves as a key component in the deposition of thin films. HMDS is employed as a primer or adhesion promoter in the deposition of photoresists, ensuring that the resist adheres firmly to the substrate during photolithography processes. This property is vital for the production of high-precision electronic components, where the quality of thin film adhesion directly impacts the performance and reliability of the final product.

Another notable application of hexamethyldisilazane is in the field of chromatography, particularly in the preparation of stationary phases for gas chromatography (GC). Its ability to react with silica gel to form a silylated surface makes it an effective reagent in the modification of chromatographic materials, improving their separation efficiency and stability under varying conditions. The silylation process provides the surface with enhanced properties, such as increased thermal stability and reduced polarity, which are beneficial for optimizing the performance of chromatographic columns.

Hexamethyldisilazane is also utilized in the synthesis of other silane derivatives and as a precursor for the production of silicon-containing materials. It plays an important role in the development of polymeric materials, as the methyl groups attached to the silicon atoms can interact with polymer chains, leading to the formation of flexible and durable materials. Additionally, its ability to introduce silicon functionality into organic molecules has made it valuable in the design of hybrid organic-inorganic systems with tailored properties.

In summary, hexamethyldisilazane is a highly versatile chemical that has found widespread use in surface modification, semiconductor manufacturing, chromatography, and the synthesis of advanced materials. Its unique properties, including its ability to form stable bonds with siliceous surfaces and enhance the performance of materials, ensure its continued relevance across a broad range of industrial applications. As research continues, the potential applications of HMDS are likely to expand, particularly in areas related to nanotechnology and advanced material design.

References

2008. Photolithographic patterning of organosilane monolayer for generating large area two-dimensional B lymphocyte arrays. Lab on a Chip, 8(12).
DOI: 10.1039/b810329a

2013. Fast quantification of amino acids by microchip electrophoresis-mass spectrometry. Analytical and Bioanalytical Chemistry, 405(24).
DOI: 10.1007/s00216-013-7260-z

2016. Facile Synthesis of Smart Nanocontainers as Key Components for Construction of Self-Healing Coating with Superhydrophobic Surfaces. Nanoscale Research Letters, 11(1).
DOI: 10.1186/s11671-016-1444-3