Hexamethyldisilazane

161.395

161.39

213-668-5

H36C68P1BH

252161|93895

2924|2920

DTXSID2025395

Colorless liquid

2929909090

12

2.62 /Estimated/

Hexamethyl disilazane appears as a liquid. May be toxic by ingestion. Irritates skin and eyes. Vapors are heavier than air. May emit highly toxic nitrogen oxide fumes when heated to decomposition. Used to make other chemicals.

0.7741 g/cm³ @ Temp: 25 °C

-78 °C

125 °C

14 deg C (closed cup) /from table/

1.4069-1.4089

In water, 392 mg/l @ 25 deg C /Estimated/

2-8ºC

20 hPa (20 °C)

LDLO i.p. in mice: 650 mg/kg (Petrarch Systems Inc. Product Information Sheets)

Ammonia-like odor

Henry's Law constant = 8.69X10-5 atm cu-m/mol at 25 °C /Estimated/

pKa = 7.55

Dielectric constant (1000 Hz) = 2.27|Hydroxyl radical reaction rate constant = 8.98X10-13 cu-cm/molc sec /Estimated/

Highly flammable. Moisture sensitive.

Reducing Agents, Strong

Highly Flammable

HEXAMETHYL DISILAZANE reacts with many carbonyl-containing organic compounds to generate gaseous ammonia. May be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen may be generated in combination with stronger reducing agents, such as hydrides.

325 °C at 1013 hPa

II

3

2920

2

R11; R20/21/22; R34

16-26-36/37/39-45-61

JM9230000

F,C,Xn

P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P273, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P307+P311, P310, P311, P312, P321, P322, P330, P337+P313, P361, P363, P370+P378, P403+P233, P403+P235, P405, P501

H225

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.

UN 3286

P210; P261; P273; P280; P302 + P352 + P312; P304 + P340 + P312

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]: Flammable/combustible material. May be ignited by heat, sparks or flames. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They will spread along ground and collect in low or confined areas (sewers, basements, tanks). Vapor explosion hazard indoors, outdoors or in sewers. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. Runoff to sewer may create fire or explosion hazard. Containers may explode when heated. Many liquids are lighter than water. (ERG, 2016)|Corrosives, Flammable - 3rd degree, Reactive - 1st degree

|Danger|H225 (76.25%): Highly Flammable liquid and vapor [Danger Flammable liquids]|P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P273, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P322, P330, P361, P363, P370+P378, P403+P233, P403+P235, P405, and P501|Aggregated GHS information provided by 557 companies from 25 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.|H225: Highly Flammable liquid and vapor [Danger Flammable liquids]|P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P307+P311, P310, P311, P312, P321, P322, P330, P337+P313, P361, P363, P370+P378, P403+P233, P403+P235, P405, and P501

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]: Some of these materials may react violently with water. SMALL FIRE: Dry chemical, CO2, water spray or alcohol-resistant foam. LARGE FIRE: Water spray, fog or alcohol-resistant foam. Move containers from fire area if you can do it without risk. Dike fire-control water for later disposal; do not scatter the material. Do not get water inside containers. FIRE INVOLVING TANKS OR CAR/TRAILER LOADS: Fight fire from maximum distance or use unmanned hose holders or monitor nozzles. Cool containers with flooding quantities of water until well after fire is out. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks engulfed in fire. For massive fire, use unmanned hose holders or monitor nozzles; if this is impossible, withdraw from area and let fire burn. (ERG, 2016)

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]: As an immediate precautionary measure, isolate spill or leak area for at least 50 meters (150 feet) in all directions. SPILL: Increase, in the downwind direction, as necessary, the isolation distance shown above. FIRE: If tank, rail car or tank truck is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2016)

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]: Fully encapsulating, vapor-protective clothing should be worn for spills and leaks with no fire. ELIMINATE all ignition sources (no smoking, flares, sparks or flames in immediate area). All equipment used when handling the product must be grounded. Do not touch or walk through spilled material. Stop leak if you can do it without risk. Prevent entry into waterways, sewers, basements or confined areas. A vapor-suppressing foam may be used to reduce vapors. Absorb with earth, sand or other non-combustible material and transfer to containers (except for Hydrazine). Use clean, non-sparking tools to collect absorbed material. LARGE SPILL: Dike far ahead of liquid spill for later disposal. Water spray may reduce vapor, but may not prevent ignition in closed spaces. (ERG, 2016)

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]: Wear positive pressure self-contained breathing apparatus (SCBA). Wear chemical protective clothing that is specifically recommended by the manufacturer. It may provide little or no thermal protection. Structural firefighters' protective clothing provides limited protection in fire situations ONLY; it is not effective in spill situations where direct contact with the substance is possible. (ERG, 2016)

Measurements of the autoignition temperatures for several series of mono-,di-, tri- and tetra-alkylsilanes showed that the ease of oxidation decrease with increasing substitution. /Hexamethylsilazane is an/ easily ignited or pyrophoric compound.

SRP: The scientific literature for the use of contact lenses in industry is conflicting. The benefit or detrimental effects of wearing contact lenses depend not only upon the substance, but also on factors including the form of the substance, characteristics and duration of the exposure, the uses of other eye protection equipment, and the hygiene of the lenses. However, there may be individual substances whose irritating or corrosive properties are such that the wearing of contact lenses would be harmful to the eye. In those specific cases, contact lenses should not be worn. In any event, the usual eye protection equipment should be worn even when contact lenses are in place.

Causes severe burns to eyes and irritation of the skin.

LD50 Rat oral 847 mg/kg bw|LD50 Mouse oral 850 mg/kg bw|LD50 Rabbit oral 1,100 mg/kg bw|LC50 Rat inhalation 8.7 mg/L/4 hr|For more Non-Human Toxicity Values (Complete) data for HEXAMETHYLDISILAZANE (8 total), please visit the HSDB record page.

Hexamethyldisilazane's production and use as a chemical intermediate, an adhesion promoter in photoresists, and a chromatographic support material(1,2) may result in its release to the environment through various waste streams(SRC).

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 390(SRC), determined from a structure estimation method(2), indicates that hexamethyldisilazane is expected to have moderate mobility in soil(SRC). Volatilization of hexamethyldisilazane from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 8.7X10-5 atm-cu m/mole(SRC), using a fragment constant estimation method(3). The potential for volatilization of hexamethyldisilazane from dry soil surfaces may exist(SRC) based upon a vapor pressure of 13.8 mm Hg(4).|AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 390(SRC), determined from a structure estimation method(2), indicates that hexamethyldisilazane may adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 8.7X10-5 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 9.9 hours and 8.9 days, respectively(SRC). The pKa of hexamethyldisilazane is 7.55(5), indicating that this compound will partially exist in cation form in the environment and cations generally adsorb more strongly to organic carbon and clay than their neutral counterparts(6). According to a classification scheme(7), an estimated BCF of 21(SRC), from an estimated log Kow of 2.6(8) and a regression-derived equation(9), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Hexamethyldisilazane is expected to hydrolyze slowly in water(5,10,11), although actual rate data for this compound were not located.|ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), hexamethyldisilazane, which has a vapor pressure of 13.8 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase hexamethyldisilazane is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 18 days(SRC), calculated from its rate constant of 9.0X10-13 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3).

The rate constant for the vapor-phase reaction of hexamethyldisilazane with photochemically-produced hydroxyl radicals has been estimated as 9.0X10-13 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 18 days at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). One study reports that hexamethyldisilazane hydrolyzes on contact with water(2). However, other sources suggest that this substance hydrolyzes more slowly(3,4). Hydrolysis rate and half-life data for hexamethyldisilazane were not found in the literature. Hexamethyldisilazane is not expected to directly photolyze due to the lack of absorption in the environmental UV spectrum (>290 nm).

An estimated BCF of 21 was calculated for hexamethyldisilazane(SRC), using an estimated log Kow of 2.6(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC).

Using a structure estimation method based on molecular connectivity indices(1), the Koc for hexamethyldisilazane can be estimated to be 390(SRC). According to a classification scheme(2), this estimated Koc value suggests that hexamethyldisilazane is expected to have moderate mobility in soil. The pKa of hexamethyldisilazane is 7.55(3), indicating that this compound will partially exist exist in cation form in the environment and cations generally adsorb more strongly to organic carbon and clay than their neutral counterparts(4).

The Henry's Law constant for hexamethyldisilazane is estimated as 8.7X10-5 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that hexamethyldisilazane is expected to volatilize from water surfaces(2). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(2) is estimated as 9.9 hours(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(2) is estimated as 8.9 days(SRC). Hexamethyldisilazane's Henry's Law constant indicates that volatilization from moist soil surfaces may occur(SRC). The potential for volatilization of hexamethyldisilazane from dry soil surfaces may exist(SRC) based upon a vapor pressure of 13.8 mm Hg(3).

Occupational exposure to hexamethyldisilazane may occur through inhalation and dermal contact with this compound at workplaces where hexamethyldisilazane is produced or used. (SRC)

Agents employed in the preparation of histologic or pathologic specimens for the purpose of maintaining the existing form and structure of all of the constituent elements. Great numbers of different agents are used; some are also decalcifying and hardening agents. They must quickly kill and coagulate living tissue. (See all compounds classified as Fixatives.)

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]: May cause toxic effects if inhaled or ingested/swallowed. Contact with substance may cause severe burns to skin and eyes. Fire will produce irritating, corrosive and/or toxic gases. Vapors may cause dizziness or suffocation. Runoff from fire control or dilution water may cause pollution. (ERG, 2016)

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]: Ensure that medical personnel are aware of the material(s) involved and take precautions to protect themselves. Move victim to fresh air. Call 911 or emergency medical service. Give artificial respiration if victim is not breathing. Do not use mouth-to-mouth method if victim ingested or inhaled the substance; give artificial respiration with the aid of a pocket mask equipped with a one-way valve or other proper respiratory medical device. Administer oxygen if breathing is difficult. Remove and isolate contaminated clothing and shoes. In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes. In case of burns, immediately cool affected skin for as long as possible with cold water. Do not remove clothing if adhering to skin. Keep victim calm and warm. Effects of exposure (inhalation, ingestion or skin contact) to substance may be delayed. (ERG, 2016)

/HUMAN EXPOSURE STUDIES/ During many years of production no case of skin burns has been observed although there has been skin contact with the product by accident. This may be explained by the high volatility of the substance. Skin irritation tests in animals have been conducted under occlusion.

hexamethyldisilazane

(1980) About 303X10+3 L of 100% active HMDS was consumed by the semiconductor industry in the United States.

1,1,1,3,3,3-Hexamethyldisilazane is available in concentrations ranging in activity from 5 to 100%. In solutions, HMDS is normally mixed with solvents such as xylene, stoddard solvent, ethylene glycol and carbon tetrafluoride.

Adhesive manufacturing|Silanamine, 1,1,1-trimethyl-N-(trimethylsilyl)-: ACTIVE|All HMDS is sold as electronic-grade material, indicating that the level of each metal impurity is less than 1 ppm.

Fire Hazards -> Corrosives, Flammable - 3rd degree, Reactive - 1st degree