Hexamethyldisilazane

This chemical does not meet GHS hazard criteria for 5.8% (35 of 606) of reports.

H225 (93.7%): Highly Flammable liquid and vapor [Danger Flammable liquids]

H302+H332 (27.1%): Harmful if swallowed or if inhaled [Warning Acute toxicity, oral; acute toxicity, inhalation]

H302 (93.9%): Harmful if swallowed [Warning Acute toxicity, oral]

H311 (88.6%): Toxic in contact with skin [Danger Acute toxicity, dermal]

H314 (31.8%): Causes severe skin burns and eye damage [Danger Skin corrosion/irritation]

H332 (89.9%): Harmful if inhaled [Warning Acute toxicity, inhalation]

H412 (85.5%): Harmful to aquatic life with long lasting effects [Hazardous to the aquatic environment, long-term hazard]

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, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 606 reports by companies from 27 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Reported as not meeting GHS hazard criteria per 35 of 606 reports by companies.

There are 26 notifications provided by 571 of 606 reports by companies with hazard statement code(s).

Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown. For more detailed information, please visit ECHA C&L website.

H225: Highly Flammable liquid and vapor [Danger Flammable liquids]

H302: Harmful if swallowed [Warning Acute toxicity, oral]

H311: Toxic in contact with skin [Danger Acute toxicity, dermal]

H314: Causes severe skin burns and eye damage [Danger Skin corrosion/irritation]

H320: Causes eye irritation [Warning Serious eye damage/eye irritation]

H331: Toxic if inhaled [Danger Acute toxicity, inhalation]

H335: May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation]

H336: May cause drowsiness or dizziness [Warning Specific target organ toxicity, single exposure; Narcotic effects]

H370: Causes damage to organs [Danger Specific target organ toxicity, single exposure]

H402: Harmful to aquatic life [Hazardous to the aquatic environment, acute hazard]

H412: Harmful to aquatic life with long lasting effects [Hazardous to the aquatic environment, long-term hazard]

P210, P233, P240, P241, P242, P243, P260, P261, P262, P264, P264+P265, P270, P271, P273, P280, P301+P317, P301+P330+P331, P302+P352, P302+P361+P354, P303+P361+P353, P304+P340, P305+P351+P338, P305+P354+P338, P308+P316, P316, P319, P321, P330, P337+P317, P361+P364, P363, P370+P378, P403+P233, P403+P235, P405, and P501 (click each P-code to see the statement)

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]:

Refer to the "General First Aid" section. Specific First Aid: For corrosives, in case of contact, immediately flush skin or eyes with running water for at least 30 minutes. Additional flushing may be required. In case of burns, immediately cool affected skin for as long as possible with cold water. Do not remove clothing if adhering to skin. (ERG, 2024)

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. If it can be done safely, move undamaged containers away from the area around the fire. Dike runoff from fire control for later disposal. Do not get water inside containers.

FIRE INVOLVING TANKS, RAIL TANK CARS OR HIGHWAY TANKS: Fight fire from maximum distance or use unmanned master stream devices 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 in direct contact with flames. For massive fire, use unmanned master stream devices or monitor nozzles; if this is impossible, withdraw from area and let fire burn. (ERG, 2024)

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]:

IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area for at least 50 meters (150 feet) in all directions.

SPILL: Increase the immediate precautionary measure distance, in the downwind direction, as necessary.

FIRE: If tank, rail tank car or highway tank 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, 2024)

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.

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.

Excerpt from ERG Guide 132 [Flammable Liquids - Corrosive]:

ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from 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. For hydrazine, absorb with DRY sand or inert absorbent (vermiculite or absorbent pads). 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, 2024)

5.8 [mg/m3]

64 [mg/m3]

380 [mg/m3]

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 when there is NO RISK OF FIRE. Structural firefighters' protective clothing provides thermal protection but only limited chemical protection. (ERG, 2024)

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.

Liquid; Other Solid

Colorless liquid

Ammonia-like odor

125 °C @760 [mm Hg]

48 °F (NFPA, 2010)

81 °F (27 °C) closed cup

14 °C (closed cup) /from table/

Soluble in acetone, benzene, ethyl ether, heptane, perchloroethylene

Insol in water, reacts slowly

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

0.7741 g/cu cm at 25 °C

0.76 @25 °C

13.8 [mmHg]

13.8 mm Hg at 25 °C

13.8 [mm Hg] @25 °C

log Kow = 2.62 /Estimated/

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

325 °C at 1013 hPa

0.90 centistokes

Index of refraction = 1.4090 @ 20 °C

pKa = 7.55

Dielectric constant (1000 Hz) = 2.27

Hydroxyl radical reaction rate constant = 8.98X10-13 cu-cm/molc sec /Estimated/

15N nuclear magnetic resonance spectrum

29Si nuclear magnetic resonance spectrum

Schoenflies notation

Chemical bond

Chemical shift

Crystal structure

Dielectric constant

Fusion temperature

Internuclear distance

Melting temperature

Molar mass

Molecular structure

Optical coefficient

Phase transition

Point group

Refractive index

Highly flammable. Moisture sensitive.

Reducing Agents, Strong

Highly Flammable

Strong Reducing Agent

Water-Reactive

Air-Reactive

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.

Dermatotoxin - Skin burns.

Toxic Pneumonitis - Inflammation of the lungs induced by inhalation of metal fumes or toxic gases and vapors.

LC50 (rat) =8,700 mg/m3/4h

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.

/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.

/LABORATORY ANIMALS: Acute Exposure/ /In an acute oral study using mice/ ...at 300 and 450 mg/kg sedation was observed, at higher dose levels up to 1500 mg/kg: difficult breathing, ataxia and hyperexcitability followed by a "prolonged" narcosis with loss of righting reflex.

/LABORATORY ANIMALS: Acute Exposure/ 4 hr application /to rabbit skin/ resulted in severe erythema, moderate to severe edema and necrosis on all six rabbits. 1 hr application produced moderate erythema, minor to moderate edema and necrosis on each of six rabbits.

/GENOTOXICITY/ Negative with and without activation in the Escherichia coli reverse mutation assay 0-5,000 ug/plate.

/GENOTOXICITY/ Negative with and without activation in the Ames test using Salmonella typhimurium TA 98, TA 100, TA 1535, TA 1537, TA 1538 0-5,000 ug/plate.

/ALTERNATIVE IN VITRO TESTS/ The ability of two commercial in-vitro assays to predict the skin irritancy and corrosivity potential of organosilicon compounds was examined. The Skin2 1350 and CORROSITEX assays were used to evaluate skin irritancy of hexamethyldisiloxane. ...CORROSITEX classified hexamethyldisilazane as corrosive, whereas the in-vivo test indicated that it was only minimally irritating.

LC50 Pimephales promelas (Fathead minnow) 167 mg/L/96 hr; static

LC50 Daphnia magna (Waterflea) 186 mg/L/48 hr /Conditions of bioassay not specified in source examined/

Hexamethyldisilazane's production and use as a chemical intermediate, an adhesion promoter in photoresists, and a chromatographic support material may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 13.8 mm Hg at 25 °C indicates hexamethyldisilazane will exist solely as a vapor in the ambient atmosphere. Vapor-phase hexamethyldisilazane will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 18 days. If released to soil, hexamethyldisilazane is expected to have moderate mobility based upon an estimated Koc of 390. Volatilization from moist soil surfaces is expected to be an important fate process based upon an estimated Henry's Law constant of 8.7X10-5 atm-cu m/mole. The pKa of hexamethyldisilazane is 7.55, 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. Hexamethyldisilazane may volatilize from dry soil surfaces based upon its vapor pressure. If released into water, hexamethyldisilazane may adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is expected to be an important fate process based upon this compound's estimated Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 9.9 hours and 8.9 days, respectively. An estimated BCF of 21 suggests the potential for bioconcentration in aquatic organisms is low. One study reports that hexamethyldisilazane hydrolyzes on contact with water. However, other sources suggest that this substance hydrolyzes more slowly. Hydrolysis rate and half-life data for hexamethyldisilazane were not found in the literature. Occupational exposure to hexamethyldisilazane may occur through inhalation and dermal contact with this compound at workplaces where hexamethyldisilazane is produced or used. (SRC)

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)

LC50 Pimephales promelas (Fathead minnow) 167 mg/L/96 hr; static

LC50 Daphnia magna (Waterflea) 186 mg/L/48 hr /Conditions of bioassay not specified in source examined/

Hexamethyldisilazane's production and use as a chemical intermediate, an adhesion promoter in photoresists, and a chromatographic support material may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 13.8 mm Hg at 25 °C indicates hexamethyldisilazane will exist solely as a vapor in the ambient atmosphere. Vapor-phase hexamethyldisilazane will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 18 days. If released to soil, hexamethyldisilazane is expected to have moderate mobility based upon an estimated Koc of 390. Volatilization from moist soil surfaces is expected to be an important fate process based upon an estimated Henry's Law constant of 8.7X10-5 atm-cu m/mole. The pKa of hexamethyldisilazane is 7.55, 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. Hexamethyldisilazane may volatilize from dry soil surfaces based upon its vapor pressure. If released into water, hexamethyldisilazane may adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is expected to be an important fate process based upon this compound's estimated Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 9.9 hours and 8.9 days, respectively. An estimated BCF of 21 suggests the potential for bioconcentration in aquatic organisms is low. One study reports that hexamethyldisilazane hydrolyzes on contact with water. However, other sources suggest that this substance hydrolyzes more slowly. Hydrolysis rate and half-life data for hexamethyldisilazane were not found in the literature. Occupational exposure to hexamethyldisilazane may occur through inhalation and dermal contact with this compound at workplaces where hexamethyldisilazane is produced or used. (SRC)

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)

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.

Flammable Liquid Corrosive