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Chemical Fact Sheet

Chemical Abstract Number (CAS #) 1634044
CASRN 1634-04-4
SynonymsMethyl tert-butyl ether
MTBE
Analytical Method EPA Method 524.2
Molecular FormulaC5H12O

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).
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).
Apparent Color Colorless liquid
Boiling Point 55.2 DEG C
Melting Point FP: -109 DEG C
Molecular Weight 88.15
Density 0.7405 @ 20 DEG C/4 DEG C
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. .
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 .
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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