2,6-Diethylaniline

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 457(SRC), determined from a structure estimation method(2), indicates that 2,6-diethylaniline is expected to have moderate mobility in soil(SRC). However, aromatic amines (including anilines) bind to humic material found in soil in two phases(3). Initially, a rapid, reversible equilibrium is established, which may represent formation of imine linkages with the humic carbonyls(3). Subsequently, there is a slow reaction that is not readily reversed(3). Also, the pKa value for 2,6-diethylaniline is expected to be approximately 4.30(4) based on its structural similarity with 2-ethylaniline. This suggests that 2,6-diethylaniline will exist partially in the protonated form in moist soils and the protonated form of 2,6-diethylaniline is expected to bind strongly to soil surfaces and not volatilize(SRC). Volatilization of the neutral species from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.1X10-6 atm-cu m/mole(SRC), from its vapor pressure, 3.83X10-3 mmHg(5), and water solubility, 670 mg/l(6). 2,6-Diethylaniline is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(5). More than 40 and 75% of 2,6-diethylaniline disappeared after 5 and 20 hrs incubation in a soil-water slurry, respectively, suggesting that biodegradation may be an important degradation pathway in soil systems(7).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 457(SRC), determined from an estimation method(2), indicates that 2,6-diethylaniline is expected to adsorb slightly to sediment and suspended solids in water(SRC). However, aromatic amines (including anilines) bind to humic material found in water in two phases(3). Initially, a rapid, reversible equilibrium is established, which may represent formation of imine linkages with the humic carbonyls(3). Subsequently, there is a slow reaction that is not readily reversed(3). Volatilization of the neutral species from water surfaces is expected(4) based upon an estimated Henry's Law constant of 1.1X10-6 atm-cu m/mole(SRC), from its vapor pressure, 3.83X10-3(5), and water solubility, 670 mg/l(6). Using this Henry's Law constant and an estimation method(4), volatilization half-lives for a model river and model lake are 27 and 295 days, respectively(SRC). However, the protonated form of 2,6-diethylaniline does not volatilize from water surfaces(SRC). More than 40 and 75% of 2,6-diethylaniline disappeared after 5 and 20 hrs incubation in a soi-water slurry, respectively, suggesting that biodegradation may be an important degradation pathway in aqueous environments(7). According to a classification scheme(8), a BCF of 120(9) suggests bioconcentration in aquatic organisms is high.

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 2,6-diethylaniline, which has a vapor pressure of 3.83X10-3 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase 2,6-diethylaniline 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 2.4 hrs(SRC), calculated from its rate constant of 1.6X10-10 cu cm/molecule-sec at 25 °C determined using a structure estimation method(3).

Using a structure estimation method based on molecular connectivity indices(1), the Koc for 2,6-diethylaniline can be estimated to be 457(SRC). According to a classification scheme(2), this estimated Koc value suggests that 2,6-diethylaniline is expected to have moderate mobility in soil. However, aromatic amines (including anilines) bind to humic material found in soil in two phases(3). Initially, a rapid, reversible equilibrium is established, which may represent formation of imine linkages with the humic carbonyls(3). Subsequently, there is a slow reaction that is not readily reversed(3). Also, the pKa value for 2,6-diethylaniline is expected to be approximately 4.30(4) based on its structural similarity with 2-ethylaniline. This suggests that 2,6-diethylaniline will exist partially in the protonated form in moist soils and the protonated form of 2,6-diethylaniline is expected to bind strongly to soil surfaces(SRC).

2,6-Diethylaniline's production and use in the manufacture of pesticides, dyestuffs, antioxidants, pharmaceuticals, synthetic resins, and fragrances(1) may result in its release to the environment through various waste streams(SRC). 2,6-Diethylaniline is found in soils as an intermediate in the microbial metabolism of certain acetanilide herbicides including alachlor(2).

2,6-Diethylaniline is degraded by the soil microorganism Chaetomium globosum to 2,6-diethylacetanilide and 2,6-diethyl-p-benzoquinone.

AEROBIC: When incubated with autoclaved soil in a water slurry, 2,6-diethylaniline disappeared slowly with about 20% of the substrate lost after 4 days(1). In comparison, 2,6-diethylaniline was transformed rapidly in nonsterile as well as in gamma-irradiated soils with concurrent accumulation of two degradation products(1). More than 40 and 75% of the applied chemical disappeared after 5 and 20 hrs incubation, respectively(1). When the pH value of the soil-water slurry was increased, the transformation of 2,6-diethylaniline and the formation of products decreased(1). At pH 3.8, about 85% of 2,6 diethylaniline was decomposed after 10 hrs incubation, while only approximately 20% of the applied chemical disappeared at pH 7.0(1). When 2,6-diethylaniline was studied in an enclosed aquatic system which simulated the environment (using various planktons, insects, and snails), it was deemed readily degradable based on the organisms abilities to quickly eliminate it(2). Contrary to the previous studies, the biodegradation of 2,6-diethylaniline was studied in both pond water and pond water amended with a sewage sludge inoculum(3). In both cases, 2,6-diethylaniline did not degrade after a 14 day exposure(3).

ANAEROBIC: When 2,6-diethylaniline was incubated at 22 °C under anaerobic conditions in an agricultural soil for 30 days, 17-32% degraded while when sludge digestor fluid was used, between 17-38% degraded(1). No degradation was observed in a sandy loam soil or in rumen fluid under these same conditions(1). In a similar study, 50 ppm of 2,6-diethylaniline was exposed to a 10% anaerobic sewage sludge inoculum incubated at 35 °C. After a 4 week exposure, there was no indication of anearobic biodegradation(2).

The Henry's Law constant for 2,6-diethylaniline is estimated as 1.1X10-6 atm-cu m/mole(SRC) from its vapor pressure, 3.83X10-3 mm Hg(1), and water solubility, 670 mg/l(2). This Henry's Law constant indicates that the neutral species is expected to volatilize from water surfaces(3). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(3) is estimated as 27 days(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(3) is estimated as 295 days(SRC). However, volatilization from water surfaces may be attenuated by adsorption to humic material in the water column(4). 2,6-Diethylaniline is expected to have a pKa value of approximately 4.30(5) based on its structural similarity with 2-ethylaniline. The protonated form of 2,6-diethylaniline does not volatilize from water surfaces(SRC). 2,6-Diethylaniline's estimated Henry's Law constant(1,2) indicates that volatilization of the neutral species from moist soil surfaces may occur(SRC). 2,6-Diethylaniline is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 3.83X10-3 mm Hg(1).

The rate constant for the vapor-phase reaction of 2,6-diethylaniline with photochemically-produced hydroxyl radicals has been estimated as 1.6X10-10 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 2.4 hrs at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). 2,6-Diethylaniline is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups(2). In general, anilines absorb light in the environmental UV spectrum (>290 nm)(3). Based on this, 2,6-diethylaniline is expected to absorb light and may potentially undergo direct photolysis(SRC).

2,6-Diethylaniline's production and use in the manufacture of pesticides, dyestuffs, antioxidants, pharmaceuticals, synthetic resins, and fragrances may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 3.83X10-3 mm Hg at 25 °C indicates 2,6-diethylaniline will exist solely in the vapor-phase in the ambient atmosphere. Vapor-phase 2,6-diethylaniline will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 2.4 hrs. If released to soil, 2,6-diethylaniline is expected to have moderate mobility based upon an estimated Koc of 457. However, aromatic amines (including anilines) bind to humic material found in soil in two phases which could decrease movement in soil. Also, the pKa value for 2,6-diethylaniline is expected to be approximately 4.30 based on its structural similarity with 2-ethylaniline. This suggests that 2,6-diethylaniline will exist partially in the protonated form in moist soils and the protonated form of 2,6-diethylaniline is expected to bind strongly to soil surfaces and not volatilize. Volatilization of the neutral species from moist soil surfaces is expected to be an important fate process based upon an estimated Henry's Law constant of 1.1X10-6 atm-cu m/mole. If released into water, 2,6-diethylaniline is expected to adsorb slightly to sediment and suspended solids in water based upon the estimated Koc. More than 40 and 75% of 2,6-diethylaniline disappeared after 5 and 20 hrs incubation in a soil-water slurry, respectively suggesting that biodegradation may be an important degradation pathway in soil and aqueous environments. Volatilization of the neutral species from water surfaces is expected to be an important fate process based upon this compound's estimated Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 27 and 295, respectively. However, volatilization from water surfaces may be attenuated by adsorption to humic material in the water column. The protonated form of 2,6-diethylaniline does not volatilize from water surfaces. A BCF of 120 suggests bioconcentration in aquatic organisms is high. Hydrolysis is not expected to occur due to the lack of hydrolyzable functional groups. Occupational exposure to 2,6-diethylaniline may occur through inhalation and dermal contact with this compound at workplaces where 2,6-diethylaniline is produced or used. (SRC)