2,2-Dimethylpropane

CAS RN: 463-82-1

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 500(SRC), determined from a structure estimation method(2), indicates that 2,2-dimethylpropane is expected to have moderate mobility in soil(SRC). Volatilization of 2,2-dimethylpropane from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 2.2 atm-cu m/mole(SRC), based upon its vapor pressure, 1290 mm Hg(3), and water solubility, 33.2 mg/L(4). 2,2-Dimethylpropane is expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(3). The highly branched structure of 2,2-dimethylpropane suggests that biodegradation in soil will be slow(5).
AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 500(SRC), determined from a structure estimation method(2), indicates that 2,2-dimethylpropane is expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 2.2 atm-cu m/mole(SRC), derived from its vapor pressure, 1290 mm Hg(4), and water solubility, 33.2 mg/L(5). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 2.5 hours and 3.4 days, respectively(SRC). 2,2-Dimethylpropane is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(3). According to a classification scheme(6), an estimated BCF of 52(SRC), from its log Kow of 3.11(7) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is moderate(SRC). The highly branched structure of 2,2-dimethylpropane suggests that biodegradation in water will be slow(8).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 2,2-dimethylpropane, which has a vapor pressure of 1290 mm Hg at 25 deg C(2), is expected to exist solely as a gas in the ambient atmosphere. Gas-phase 2,2-dimethylpropane 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 19 days(SRC), calculated from its rate constant of 8.25X10-13 cu cm/molecule-sec at 25 deg C(3). 2,2-Dimethylpropane does not contain chromophores that absorb at wavelengths >290 nm(4) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).
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