| Chemical Abstract Number (CAS #) |
1634044
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| CASRN |
1634-04-4 |
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| Synonyms | Methyl tert-butyl ether |
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MTBE |
| Analytical Method |
EPA Method 524.2 |
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| Molecular Formula | C5H12O |
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Link to the National Library of Medicine's Hazardous Substances
Database for more details
on this compound. |
| Use | Octane booster in gasoline.
Manufacture of isobutene
Unleaded gasoline usually contains additives for octane improvement including methyl
tert-butyl ether (MTBE).
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| Consumption Patterns | Gasoline octane component, 100%.
CHEMICAL PROFILE: Methyl tert-butyl ether. Demand: 1988: 65,500 barrels per day; 1989:
72,500 barrels per day; 1993 projected/: 90,000 barrels per day (average daily consumption;
foreign trade is negligible).
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| Apparent Color | Colorless liquid
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| Boiling Point | 55.2 DEG C
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| Melting Point | FP: -109 DEG C
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| Molecular Weight | 88.15
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| Density | 0.7405 @ 20 DEG C/4 DEG C
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| Environmental Impact | t-Butyl methyl ether may be released as a result of its use as an octane booster for
unleaded gasoline and its use in the manufacture of isobutene. If t-butyl methyl ether is released to
soil, it will be subject to volatilization. It will be expected to exhibit very high mobility in soil and,
therefore, it may leach to groundwater. It will not be expected to hydrolyze in soil. If t-butyl
methyl ether is released to water, it will not be expected to significantly adsorb to sediment or
suspended particulate matter, bioconcentrate in aquatic organisms, hydrolyze, directly photolyze,
or photooxidize via reaction with photochemically produced hydroxyl radicals in the water, based
upon estimated physical-chemical properties or analogies to other structurally related aliphatic
ethers. t-Butyl methyl ether in surface water will be subject to rapid volatilization with estimated
half-lives of 4.1 hr and 2.0 days for volatilization from a river one meter deep flowing 1 m/sec
with a wind velocity of 3 m/sec and a model pond, respectively. It may be resistent to
biodegradation in environmental media based upon screening test data from a study using
activated sludge inocula. Many ethers are known to be resistant to biodegradation. If t-butyl
methyl ether is released to the atmosphere, it will be expected to exist almost entirely in the vapor
phase based on its vapor pressure. It will be susceptible to photoxidation via vapor phase reaction
with photochemically produced hydroxyl radicals with an estimated half-life of 5.6 days for this
process. Direct photolysis will not be an important removal process since aliphatic ethers do not
adsorb light at wavelenghts >290 nm. The most probable route of general population exposure to
t-butyl methyl ether is probably via inhalation of contaminated air. Exposures through dermal
contact may occur in occupational settings. .
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| Environmental Fate | TERRESTRIAL FATE: If t-butyl methyl ether is released to soil, it will be subject to
volatilization based upon a reported Henry's Law constant of 5.87X10-4 atm-cu m/mole and
vapor pressure of 249 mm Hg at 25 deg C . It will be expected to exhibit very high
mobility(5,SRC) in soil and, therefore, it may leach to groundwater, based upon an estimated Koc
of 11.2(3,4,SRC). It will not be expected to hydrolyze in soil . Butyl methyl ether may be
resistent to biodegradation in soil based upon screening test data from a study using activated
sludge inocula(6,SRC). Many ethers are known to be resistant to biodegradation(7).
AQUATIC FATE: If t-butyl methyl ether is released to water, it will not be expected to
significantly adsorb to sediment or suspended particulate matter(1,2,SRC), bioconcentrate in
aquatic organisms(1,2,SRC), hydrolyze , directly photolyze , or photooxidize via reaction
with photochemically produced hydroxyl radicals in the water , based upon estimated
physical-chemical properties or analogies to other structurally related aliphatic ethers(1-3,SRC).
t-Butyl methyl ether in surface water will be subject to rapid volatilization(2,5,SRC). Using a
reported Henry's Law constant of 5.87X10-4 atm-cu m/mole , a half-life for volatilization of
t-butyl methyl ether from a river one meter deep flowing 1 m/sec with a wind velocity of 3 m/sec
has been estimated to be 4.1 hr at 25 deg C(2,SRC). The volatilization half-life from a model
pond, which considers the effect of adsorption, has been estimated to be 2.0 days(6). t-Butyl
methyl ether may be resistent to biodegradation in environmental media based upon screening test
data from a study using activated sludge inocula(7,SRC). Many ethers are known to be resistant
to biodegradation(8).
ATMOSPHERIC FATE: If t-butyl methyl ether is released to the atmosphere, it will be
expected to exist almost entirely in the vapor phase based upon a reported vapor pressure of
249 mm Hg at 25 deg C . It will be susceptible to photooxidation via vapor phase reaction with
photochemically produced hydroxyl radicals. An atmospheric half-life of 5.6 days at an
atmospheric concentration of 5X10 5 hydroxyl radicals per cu cm has been calculated for this
process based upon a measured rate constant(1,SRC). Direct photolysis will not be an important
removal process since aliphatic ethers do not absorb light at wavelengths >290 nm .
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| Drinking Water Impact | GROUNDWATER: t-Butyl methyl ether has been detected at concn up to 50 ppb in the
Old Bridge aquifer under an industrial plant in South Brunswick Township, NJ (no sampling dates
specified) . A contamination abatement system installed at this aquifer, including 7 extraction
wells and a water treatment facility, reduced the t-butyl methyl ether concn by an estimated
26% .
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