Mechlorethamine

CAS RN: 51-75-2

Environmental Fate

TERRESTRIAL FATE: The hydrolysis of mechlorethamine is generally described as rapid(1,2). A hydrolysis half-life of 11 hours was reported for mechlorethamine in a 66.7% acetone-water solution at 25 deg C(3), and would be expected to be more rapid in a solution with just water as the solvent (SRC). The predominate environmental fate of mechlorethamine is expected to be hydrolysis, and it will not be expected to leach in soil(SRC). Mechlorethamine is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 0.17 mm Hg at 25 deg C(1).
AQUATIC FATE: The hydrolysis of mechlorethamine is generally described as rapid(1,2). A hydrolysis half-life of 11 hours was reported for mechlorethamine in a 66.7% acetone-water solution at 25 deg C(3), and would be expected to be more rapid in a solution with just water as the solvent(SRC). The predominate environmental fate of mechlorethamine is expected to be hydrolysis and therefore bioconcentration is not expected to be an important environmental fate process(SRC). The hydrolysis of mechlorethamine may be limited by its rate of dissolution(SRC) as is seen for a related compound, bis(2-chloroethyl)sulfide (mustard gas)(4).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), mechlorethamine, which has a vapor pressure of 0.17 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase mechlorethamine 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 2 days(SRC), calculated from its rate constant of 8.4X10-12 cu cm/molecule-sec at 25 deg C(SRC) that was derived using a structure estimation method(3). Mechlorethamine does not contain any functional groups that would be expected to absorb light with wavelengths >290 nm, and it would not be expected to be susceptible to direct photolysis by sunlight(SRC).
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