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Hexamethyldisilazane(HMDS) , colorless transparent liquid. It is easy to hydrolyze, release NH3, and generate hexamethyldisilane. In the presence of catalyst, it reacts with alcohol or phenol to produce trimethylalkoxysilane or trimethylaryloxysilane. It reacts with anhydrous hydrogen chloride to release NH3 or NH4Cl to produce trimethylchlorosilane. It can be prepared by reacting trimethylchlorosilane with NH3. It can be used as a hydrophobic treatment agent for the surface of fumed silica and a reagent to provide N atoms in organic synthesis reaction, as an auxiliary agent for silicon carbide fibers, to improve the heat resistance and strength of silicon carbide fibers, and as an anti precipitation agent for coatings. It is also used to prepare organosilicon compounds.
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Chemical Formula |
C6H19NSi2 |
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Exact Mass |
161.11 |
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Molecular Weight |
161.40 |
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m/z |
161.11 (100.0%), 162.11 (6.5%), 162.11 (5.1%), 162.11 (5.1%), 163.10 (3.3%), 163.10 (3.3%) |
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Elemental Analysis |
C, 44.65; H, 11.87; N, 8.68; Si, 34.80 |
Hexamethyldisilazane(HMDS) (CAS number: 999-97-3), as a multifunctional organic silicon compound, has demonstrated irreplaceable value in various fields such as medicine, semiconductor, organic synthesis, and material modification due to its unique silicon nitrogen bond (Si-N) structure and high reactivity.
The application of HMDS in the pharmaceutical field accounts for 64%, and it is the core reagent for the synthesis of antibiotics, anti-tumor drugs, antiviral drugs, and targeted drug carriers. Its core value is reflected in the dual functions of group protection and reaction activation:
Antibiotic synthesis
β - lactam antibiotics (such as penicillin and cephalosporin): HMDS protects hydroxyl or amino groups through silanization, preventing key intermediates from decomposing under acidic or high-temperature conditions. For example, in the synthesis of cephalosporin antibiotics, HMDS protects the hydroxyl group of 7-aminocephalosporanic acid (7-ACA), increasing the reaction yield from 65% to 89% while reducing the generation of by-products.
Aminoglycoside antibiotics (such as amikacin and kanamycin): HMDS protects the amino group to ensure the stability of the reaction pathway. In the synthesis of amikacin, the introduction of HMDS increased the purity of the intermediate from 92% to 98%, significantly improving the efficiency of large-scale production.
antineoplastic drugs
Fluorouracil (5-FU): HMDS protects the hydroxyl groups of drug intermediates through silanization, reducing oxidative side reactions. Experimental data shows that after using HMDS, the synthesis steps of fluorouracil were simplified from 7 steps to 4 steps, the yield increased from 58% to 76%, and the purity reached 99.5%.
Targeted drug carrier: High purity HMDS is used to modify the surface of liposomes or polymer nanoparticles, enhancing biocompatibility and targeting. For example, the accumulation of modified anti-cancer drug carriers in tumor tissues is increased by three times, and systemic toxicity is reduced by 40%.
antiviral drugs
Azvudine: HMDS reduces the risk of impurity generation in the synthesis of new antiviral drug intermediates through multi-step protective reactions. Preclinical studies have shown that the introduction of HMDS reduces the impurity content of intermediates from 2.1% to 0.3%, supporting large-scale production with an annual capacity of over 50 tons.
Semiconductor industry: the "bonding expert" of photolithography technology
In the semiconductor field, Hexamethyldisilazane(HMDS), as a bonding agent for photo etchants, improves chip manufacturing accuracy through surface modification technology, accounting for 20% of applications. Its core mechanism of action is:
Surface hydrophobicity treatment
HMDS is sprayed onto the surface of silicon wafers in liquid or gas phase, and the silicon nitrogen bond condenses with the silicon hydroxyl group (- Si OH) to form a hydrophobic silicon nitride layer (contact angle increases from 20 ° to 120 °), which increases the adhesion between the photoresist and the silicon wafer by three times, reduces the penetration depth of the etching solution by 80%, and significantly enhances the corrosion resistance.
Electronic grade product applications
Electronic grade HMDS (purity ≥ 99.999%) has been widely used in fields such as flat panel displays and chip manufacturing. For example, in 12 inch wafer processing, HMDS processing reduces the photoresist stripping rate from 15% to 3%, controls the line width uniformity within ± 2nm, and supports processes of 5nm and below.
Organosilicon materials: key modifiers for performance improvement
HMDS accounts for 3% of the application in the field of organosilicon, and is the core additive for optimizing the properties of materials such as silicone rubber, silicone oil, and silicone resin
Silicone rubber reinforcement
HMDS, as a sealing agent, reacts with the hydroxyl groups at the end of the silicone rubber molecular chain through silicon nitrogen bonds to form a stable cross-linked structure. Experiments have shown that adding 2% HMDS to silicone rubber increases its tear strength by 40%, expands its temperature resistance range from -50 ℃ to 200 ℃ to -80 ℃ to 250 ℃, and reduces its compression set by 50%.
Hydrophobic treatment of silicone oil
HMDS reacts with the silanol groups on the surface of gas-phase white carbon black to form a hydrophobic silazane layer, increasing the contact angle of silicone oil from 30 ° to 150 ° and reducing defoaming time by 60%. It is widely used in coatings, cosmetics and other fields.
High temperature lubricant additive
HMDS combines with lubricating oil molecules to form a protective film, reducing volatility by 30%, prolonging the oxidation induction period by 2 times, and increasing thermal stability to 300 ℃. It is suitable for high-temperature environments such as aircraft engines.
Material surface treatment: a "master key" for functional modification
HMDS achieves performance optimization by condensing hydroxyl groups on the surface of inorganic materials through silicon nitrogen bonds, with an application proportion of 8%
Powder material processing
White carbon black: After HMDS treatment, the specific surface area decreased from 200m ²/g to 180m ²/g, the agglomeration phenomenon was reduced by 70%, and the dispersibility in rubber was significantly improved.
Titanium powder: Surface hydrophobicity treatment reduces the settling rate of titanium powder in organic solvents by 90%, making it suitable for 3D printing metal powder preparation.
Fiber fabric modification
HMDS treatment of silicon carbide fibers forms a silicon nitride protective layer, increasing the fiber's heat resistance from 1200 ℃ to 1500 ℃ and strength retention rate from 65% to 85%. It is widely used in aerospace composite materials.
Hexamethyldisilazane(HMDS) accounts for 5% in the field of organic synthesis, and its core applications include:
Synthesis of Chlorosilane Monomer
HMDS undergoes chlorine exchange reaction with chlorosilanes (such as octamethylcyclotetrasiloxane) to generate polysilazane, with a yield 20% higher and energy consumption reduced by 30% compared to direct ammonia method. It is an important method for preparing ceramic precursors.
Gas chromatography tail reducer
As a fixed liquid, HMDS reduces the surface adsorption activity of the carrier, increases peak symmetry by 40%, and reduces the detection limit to 0.1 ppm. It is widely used in environmental monitoring, drug analysis, and other fields.
Preparation of Electron Microscope Samples
HMDS, as a critical point desiccant, replaces traditional ethanol dehydration, reduces sample shrinkage by 80%, preserves cell ultrastructure, and is widely used in biomedical research.
There are five main synthetic processes for this product:
1. Trimethylsilane reacts with ammonia under the catalysis of Pt or Pd. The reaction temperature is high and the equipment is strict. The yield is up to 95.8%.
2. Trimethylchlorosilane is prepared from trimethylchlorosilane by reacting with ammonia in inert solvent and rectifying.
3. With hexamethyldisiloxane as raw material, it reacts with concentrated sulfuric acid to generate silicon sulfate, and silicon sulfate reacts with hydrogen chloride to generate trimethylchlorosilane, and then passes ammonia to prepare HMDS.
4. Hexamethyldisiloxane reacts with phosphorus pentoxide or phosphoric acid to prepare silicon phosphate, and then enters ammonia to prepare HMDS.
5. HMDS is prepared by the reaction of hexamethyldisiloxane and concentrated sulfuric acid to produce silicon sulfate directly through ammonia gas.
At present, the second method is mainly used for industrial production of HMDS in China. This method takes trimethylchlorosilane as raw material, reacts with ammonia in inert solvent, and then is prepared by distillation.
Method 1:
Add 630ml trimethylchlorosilane, 250ml hexamethyldisiloxane, 500ml benzene and 500ml xylene into the reactor with agitator, thermometer and pressure gauge, and stir evenly. The ammonia gas is introduced for ammoniation reaction, and the change of material state in the flask is carefully observed during the process of ammonia gas introduction. Strictly control the ammonia gas flow rate, and the reaction rate should not be too fast to prevent salt particles from wrapping trimethylchlorosilane. Control reaction temperature ≤ 80 ℃ and reaction pressure ≤ 0.2Mpa. After the ammoniation reaction, cool the material to 35 ℃ and add 800ml of water for the first water washing. After washing, stand for 5 minutes and remove the NH4Cl aqueous solution in the lower layer in phases. Add 400ml of 30% potassium hydroxide solution to wash the organic phase. After washing, let it stand for 5 minutes, and then separate the lower aqueous phase. The organic phase is washed with 800ml water for the second time. After phase separation, the upper material is crude HMDS. During the washing process, the washing water for the first washing shall be the washing water for the second washing after alkali washing. The crude product is sent to the distillation tower to separate the reaction solvent and product, and finally hexamethyldisilazane with content ≥ 99% is obtained with yield of 89.99%.
Method 2:
A method for preparing hexamethyldisiloxane from hexamethyldisiloxane includes the following steps:
1) Put 1000kg hexamethyldisiloxane into a reaction vessel with a capacity of 1500L, feed dry hydrogen chloride gas into the reaction vessel for reaction, and generate trimethylchlorosilane and water; The pressure in the reaction vessel is controlled at about 0.2MPa, the temperature is 30 ℃, and the stirring speed in the reaction vessel is 65r/min. During the reaction, the generated water is discharged from the bottom of the reaction vessel.
When the mass of trimethylchlorosilane in the mixed solution of hexamethyldisiloxane and trimethylchlorosilane in the above reaction vessel accounts for 30% of the mass of the mixed solution, stop passing hydrogen chloride gas, and the reaction ends.
2) Transfer the mixture of hexamethyldisiloxane and trimethylchlorosilane obtained above to another reactor with a capacity of 3000L and stir it. Fill the reactor with dry ammonia to generate hexamethyldisiloxane and ammonium chloride. The pressure in the reactor is about 0.25MPa, the temperature is 35 ℃, and the reaction time is 5h.
3) The ammonium chloride in the reaction product in step 2) is separated through the ammonium chloride separation thickener, and then the residue is rectified to remove hexamethyldisiloxane to finally obtain hexamethyldisilazane(HMDS).
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