(L)-Ephedrine

CAS RN: 299-42-3

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 72(SRC), determined from a structure estimation method(2), indicates that (L)-ephedrine is expected to have high mobility in soil(SRC). The pKa of (L)-ephedrine is 9.65(3), indicating that this compound will exist primarily in the cation form in the environment and cations generally adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(4). Volatilization of (L)-ephedrine from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 8.7X10-11 atm-cu m/mole(SRC), using a fragment constant estimation method(2). (L)-Ephedrine is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 1.2X10-3 mm Hg at 25 deg C(SRC), determined from a fragment constant method(2). (L)-Ephedrine is reported to gradually decomposes on exposure to light(5); therefore, (L)-ephedrine may be susceptible to direct photolysis on soil surfaces exposed to sunlight(SRC). (L)-Ephedrine has been classified as readily biodegradable by sewage sludge following acclimation(6).
AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 72(SRC), determined from a structure estimation method(2), indicates that (L)-ephedrine is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 8.7X10-11 atm-cu m/mole(SRC), developed using a fragment constant estimation method(2). According to a classification scheme(4), an estimated BCF of 1.4(SRC), from its log Kow of 1.13(5) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is low(SRC). The rate constant for the reaction of hydroxyl radicals in aqueous solutions at pH 10.5 is 2.3X10+9 L/mol-sec(6); this corresponds to an aquatic half-life of 349 days at an aquatic concentration of 1X10-17 hydroxyl radicals per liter(7). (L)-Ephedrine is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(3). (L)-Ephedrine is reported to decompose gradually on exposure to light(8); therefore, (L)-ephedrine may be susceptible to direct photolysis in natural waters exposed to sunlight(SRC). (L)-Ephedrine has been classified as readily biodegradable by sewage sludge following acclimation(9).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), (L)-ephedrine, which has an estimated vapor pressure of 1.2X10-3 mm Hg at 25 deg C(SRC), determined from a fragment constant method(2), will exist solely as a vapor in the ambient atmosphere. Since(L)-ephedrine exists as a solid below its melting point of 38.1 deg C(3), occurrence in the particulate-phase may be possible(SRC). Vapor-phase (L)-ephedrine 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 4 hours(SRC), calculated from its rate constant of 1.0X10-10 cu cm/molecule-sec at 25 deg C(SRC) that was derived using a structure estimation method(2). (L)-Ephedrine is reported to decompose gradually on exposure to light(3); therefore, (L)-ephedrine may be susceptible to direct photolysis by sunlight(SRC).
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