ETHYLBENZENE

CASRN: 100-41-4; DOT: 1175; DOT label: Flammable liquid; molecular formula: C8H10; FW: 106.17; RTECS: DA0700000; Merck Index: 12, 3812 Physical state, color, and odor: Clear, colorless liquid with a sweet, gasoline-like odor. At 40 °C, the average odor threshold concentration and the lowest concentration at which an odor was detected were 550 and 150 µg/L, respectively. Similarly, at 25 °C, the average taste threshold concentration and the lowest concentration at which a taste was detected were 780 and 390 µg/L, respectively (Young et al., 1996). The average least detectable odor threshold concentrations in water at 60 °C and in air at 40 °C were 2.4 and 72 µg/L, respectively (Alexander et al., 1982). Cometto-Muñiz and Cain (1994) reported an average nasal pungency threshold concentration of 10,100 ppmv. Melting point (°C): -94.4 (Huntress and Mulliken, 1941) Boiling point (°C): 136.13-136.18 (Rintelen et al., 1937) Density (g/cm3): 0.8672 at 20.00 °C, 0.8628 at 25 °C (Nhaesi and Asfour, 2000) 0.85814 at 30.00 °C (Ramadevi et al., 1996) Diffusivity in water (x 10-5 cm2/sec): 0.81 at 20 °C (Witherspoon and Bonoli, 1969) 0.90 at 25 °C (Bonoli and Witherspoon, 1968) Dissociation constant, pKa: >15 (Christensen et al., 1975) Flash point (°C): 13 (NIOSH, 1997) Lower explosive limit (%): 0.8 (NIOSH, 1997) Upper explosive limit (%): 6.7 (NIOSH, 1997) Heat of fusion (kcal/mol): 2.195 (Dean, 1987) Henry’s law constant (x 10-3 atm⋅m3/mol): 6.6 (Pankow and Rosen, 1988) 6.279 at 22 °C (SPME-GC, Saraullo et al., 1997) 7.83 at 25 °C (EPICS-UV spectrophotometry, Allen et al., 1998)

3.26, 4.51, 6.01, 7.88, and 10.5 at 10, 15, 20, 25, and 30 °C, respectively (EPICS, Ashworth et al.,

1988) 3.02, 4.22, 5.75, 7.84, and 10.3 at 10, 15, 20, 25, and 30 °C, respectively (headspace-GC, Perlinger

et al., 1993) Distilled water: 1.93, 2.05, 2.67, 5.02, and 6.62 at 2.0, 6.0, 10.0, 18.2, and 25.0 °C, respectively;

natural seawater: 2.98 and 8.27 at 6.0 and 25.0 °C, respectively (EPICS, Dewulf et al., 1995) 6.67 at 25 °C (gas stripping-UV spectrophotometry, Mackay et al., 1979) 6.12 at 25 °C (gas purging method, Benzing et al., 1996) 7.78, 10.17, and 16.4 at 25, 30, and 40 °C, respectively (variable headspace method, Robbins et

al., 1993) 2.84 at 20 °C, 5.70 at 40 °C, 7.88 at 80 °C (batch air stripping-GC, Bobadilla et al., 2003) 13.9 at 45.00 °C, 15.1 at 50.00 °C, 17.1 at 55.00 °C, 20.1 at 60.00 °C, 20.9 at 65.00 °C, 22.7 at

70.00 °C, 34.3 at 80.00 °C (static headspace-GC, Park et al., 2004) Interfacial tension with water (dyn/cm): 38.4 at 25 °C (Donahue and Bartell, 1952) 38.70 at 20 °C (Harkins et al., 1920) 33.92 at 20 °C, 33.31 at 40 °C, 32.24 at 60 °C, 30.72 at 80 °C (Jasper and Seitz, 1959) Ionization potential (eV): 8.76 ± 0.01 (Franklin et al., 1969) Bioconcentration factor, log BCF: 1.19 (bluegill sunfish, Ogata et al., 1984) 2.41, 2.52, 2.54, 3.04, 3.20, 3.26, and 5.00 for holly, olive, grass, rosemary, ivy, mock orange,

pine, and juniper leaves, respectively (Hiatt, 1998) Soil organic carbon/water partition coefficient, log Koc: 2.22 (Woodburn silt loam soil, Chiou et al., 1983) 2.27 (St. Clair soil), 2.28 (Oshtemo soil) (Lee et al., 1989) 2.38 (estimated from HPLC capacity factors, Hodson and Williams, 1988) 2.41 (Tamar estuary sediment, Vowles and Mantoura, 1987) 2.49, 2.73, 2.65, 2.73, 2.77, 2.73, and 2.74 at 2.3, 3.8, 6.2, 8.0, 13.5, 18.6, and 25.0 °C, re-

spectively, for a Leie River (Belgium) clay (Dewulf et al., 1999a) Octanol/water partition coefficient, log Kow: 3.13 (generator column-HPLC/GC, Wasik et al., 1981, 1983) 3.14 at 25.0 °C (generator column-RPLC, Schantz and Martire, 1987) 3.15 (Campbell and Luthy, 1985; Hansch et al., 1968) 3.20 (shake flask-GC, Jaynes and Vance, 1996) 3.57 (estimated from HPLC capacity factors, Eadsforth, 1986) Solubility in organics: Freely soluble in most solvents (U.S. EPA, 1985) Solubility in water: 1.76 mM at 25 °C (generator column-HPLC/GC, Wasik et al., 1981, 1983) 1.66 mM at 25 °C (headspace analysis, Keeley et al., 1991) 187 mg/L at 25 °C (Miller et al., 1985) 152 mg/kg at 25 °C (shake flask-GC, McAuliffe, 1966)

168 mg/L solution at 25.0 °C (shake flask-UV spectrophotometry, Andrews and Keefer, 1950a) In mg/L: 219 at 0.4 °C, 213 at 5.2 °C, 207 at 20.7 °C, 207 at 21.2 °C, 208 at 25.0 °C, 209 at 25.6

°C, 211 at 30.2 °C, 221 at 34.9 °C, 231 at 42.8 °C (shake flask-UV spectrophotometry, Bohon and Claussen, 1951)

In mM: 1.850 at 10.0 °C, 1.812 at 14.0 °C, 1.776 at 17.0 °C, 1.725 at 18.0 °C, 1.676 at 19.0 °C, 1.770 at 20.0 °C, 1.724 at 21.0 °C, 1.713 at 22.0 °C, 1.751 at 23.5 °C, 1.811 at 25.0 °C, 1.753 at 25.8 °C, 1.747 at 28.0 °C, 1.777 at 30.0 °C, 1.818 at 35.0 °C, 1.928 at 40.0 °C, 1.991 at 45.0 °C (coupled-column-LC, Owens et al., 1986)

197 mg/kg at 0 °C, 177 mg/kg at 25 °C (shake flask-GC, Polak and Lu, 1973) 161.2 mg/L at 25.0 °C; 111.0 mg/L in artificial seawater at 25.0 °C (shake flask-GC, Sutton and

Calder, 1975) 131.0 mg/kg at 25 °C (shake flask-GLC, Price, 1976) 181 mg/L at 20 °C (Burris and MacIntyre, 1986) 177 mg/L at 25 °C; 170 mg/L in salt water at 25 °C (Krasnoshchekova and Gubergrits, 1975) 177 mg/L at 20 °C (air stripping-GC, Vozňáková et al., 1978) 2.00 mM at 25 °C (shake flask-UV spectrophotometry, Ben-Naim and Wilf, 1980) 1.12 mM in 0.5 M NaCl at 25 °C (Wasik et al., 1984) 175 mg/L at 25 °C (shake flask-UV spectrophotometry, Klevens, 1950) 140 mg/kg at 15 °C (shake flask-turbidimetric, Fühner, 1924) 147.7 mg/L at 30 °C (vapor equilibrium-GC, McNally and Grob, 1984) 1.51, 1.59, 1.65, and 1.83 mM at 15, 25, 35, and 45 °C, respectively (Sanemasa et al., 1982) 172 mg/L (shake flask-GC, Coutant and Keigley, 1988) 1.55 mmol/kg at 25 °C (shake flask-gravimetric, Morrison and Billett, 1952) In mg/kg: 196, 192, 186, 187, 181, 183, 180, 184, and 180 at 4.5, 6.3, 7.1, 9.0, 11.8, 12.1, 15.1,

17.9, and 20.1 °C, respectively. In artificial seawater: 140, 133, 129, 125, and 122 at 0.19, 5.32, 10.05, 14.96, and 20.04 °C, respectively (shake flask-UV spectrophotometry, Brown and Wasik, 1974)

In mg/kg: 100 at 10 °C, 107 at 20 °C, 121 at 30 °C (shake flask-UV spectrophotometry, Howe et al., 1987) 1.91 mmol/kg at 25.0 °C (shake flask-UV spectrophotometry, Vesala, 1974) 1.02 mM at 25.00 °C (Sanemasa et al., 1985) 1.37 mM at 25.0 °C (Sanemasa et al., 1987) 0.0196 wt % at 10.0 and 20.0 °C (Schwarz and Miller, 1980) In mM: 1.59 at 0.5 °C, 1.57 at 5.00 °C, 1.56 at 15.00 °C, 1.60 at 25.00 °C, 1.67 at 35.00 °C, 1.77

at 45.00 °C, 2.01 at 55.00 °C (HPLC, Dohányosová et al., 2001) In mole fraction (x 10-5) at 750 mmHg: 3.234 at 0.0 °C, 3.084 at 5.0 °C, 2.964 at 10.0 °C, 2.880 at

15.0 °C, 2.863 at 20.0 °C, 2.946 at 30.0 °C, 3.047 at 35.0 °C, 3.188 at 40.0 °C, 3.338 at 45.0 °C, 3.525 at 50.0 °C (equilibrium cell-UV spectrophotometry, Sawamura et al., 2001)

Vapor density: 4.34 g/L at 25 °C, 3.66 (air = 1) Vapor pressure (mmHg): 2.9 at 10 °C, 11.6 at 30 °C, 34.6 at 30 °C (Rintelen et al., 1937) 7.08 at 20 °C (Burris and MacIntyre, 1986) 9.6 at 25 °C (Banerjee et al., 1990) 21.5 at 40.00 °C (static method, Asmanova and Goral, 1980) Environmental fate: Biological. Phenylacetic acid was reported to be the biooxidation product of ethylbenzene by

Methylosinus trichosporium OB3b was reported to metabolize ethylbenzene to 2-and 3hydroxybenzaldehyde with methane as the substrate (Keck et al., 1989). Ethylbenzene was oxidized by a strain of Micrococcus cerificans to phenylacetic acid (Pitter and Chudoba, 1990). A culture of Nocardia tartaricans ATCC 31190, growing in a hexadecane medium, oxidized ethylbenzene to 1-phenethanol, which oxidized to acetophenone (Cox and Goldsmith, 1979). When ethylbenzene (5 mg/L) was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum, complete biodegradation with rapid acclimation was observed after 7 d. At a concentration of 10 mg/L, significant degradation occurred with gradual adaptation. Percent losses of 69, 78, 87, and 100 were obtained after 7, 14, 21, and 28-d incubation periods, respectively (Tabak et al., 1981). Olsen and Davis (1990) reported a first-order degradation rate constant of 0.07/yr and a half-life of 37 d. Elshahed et al. (2001) investigated the pathways of anaerobic biodegradation of alkylbenzenes by sediment-associated microorganisms from a gas-condensate-impacted aquifer under laboratory conditions. Stoichiometric amounts of sulfate were consumed and methane produced. Two intermediate compounds identified via GC/MS were 3-phenyl-1,2-butanedicarboxylic acid and benzoic acid. Both metabolites identified in the laboratory incubations were also identified in the contaminated aquifer from which the microorganisms were obtained. Surface Water. The evaporation half-life of ethylbenzene in surface water (1 m depth) at 25 °C is estimated to be from 5 to 6 h (Mackay and Leinonen, 1975). Estimated half-lives of ethylbenzene (3.3 µg/L) from an experimental marine mesocosm during the spring (8-16 °C), summer (20-22 °C), and winter (3-7 °C) were 20, 2.1, and 13 d, respectively (Wakeham et al., 1983). Photolytic. Irradiation of ethylbenzene (λ <2537 Å) at low temperatures will form hydrogen, styrene, and free radicals (Calvert and Pitts, 1966). Chemical/Physical. Complete combustion in air yields carbon dioxide and water vapor. Ethylbenzene will not hydrolyze in water (Kollig, 1993). De Visscher et al. (1996) investigated the sonolysis of ethylbenzene and other monocyclic aromatic compounds in aqueous solution by 520 kHz ultrasonic waves. The experiments were performed in a 200-mL glass reactor equipped with a cooling jacket maintained at 25 °C. At initial ethylbenzene concentrations and sonication times of 0.33 mM and 70 min, 0.5 mM and 100 min, and 1 mM and 140 min, the first-order reaction rates were 0.04333, 0.3564, and 0.01667/min, respectively. At an influent concentration of 115 mg/L, treatment with GAC resulted in an effluent concentration of 18 mg/L. The adsorbability of the carbon used was 18 mg/g carbon (Guisti et al., 1974). Similarly, at influent concentrations of 10.0, 1.0, 0.1, and 0.01 mg/L, the GAC adsorption capacities at pH 7.4 were 325, 53, 8.5, and 1.4 mg/g, respectively (Dobbs and Cohen, 1980). Exposure limits: NIOSH REL: TWA 100 ppm (435 mg/m3), STEL 125 ppm (545 mg/m3), IDLH 800 ppm; OSHA PEL: TWA 100 ppm; ACGIH TLV: TWA 100 ppm, STEL 125 ppm (adopted). Symptoms of exposure: Narcotic at high concentrations. Irritant to the eyes, skin, and nose (Patnaik, 1992). Toxicity: EC50 (96-h - growth inhibition) for diatoms (Skeletonema costatum) 3.6 mg/L, freshwater algae (Selenastrum capricornutum) 3.6 mg/L (Masten et al., 1994). EC50 (72-h) for Selenastrum capricornutum 4.6 mg/L (Galassi et al., 1988). LC50 (contact) for earthworm (Eisenia fetida) 47 µg/cm2 (Neuhauser et al., 1985). LC50 (96-h) for bluegill sunfish 150 mg/L (Spehar et al., 1982), Salmo gairdneri 4.2 mg/L (Galassi et al., 1988), Atlantic silversides (Menidia menidia) 5.1 mg/L, mysid shrimp (Mysidopsis

(Heitmuller et al., 1981). LC50 (72-h) for Cyprinodon variegatus 320 ppm (Heitmuller et al., 1981). LC50 (48-h) for Daphnia magna 75 mg/L (LeBlanc, 1980), Cyprinodon variegatus 360 ppm (Heitmuller et al., 1981). LC50 (24-h) for Daphnia magna 77 mg/L (LeBlanc, 1980), Cyprinodon variegatus 300 ppm (Heitmuller et al., 1981). Acute oral LD50 for rats 3,500 mg/kg (quoted, RTECS, 1985). Heitmuller et al. (1981) reported a NOEC of 88 ppm. Drinking water standard (final): MCLG: 0.7 mg/L; MCL: 0.7 mg/L. In addition, a DWEL of 3 µg/L was recommended (U.S. EPA, 2000). Source: Detected in distilled water-soluble fractions of 87 octane gasoline (2.38 mg/L), 94 octane gasoline (7.42 mg/L), Gasohol (3.54 mg/L), No. 2 fuel oil (0.21 mg/L), jet fuel A (0.41 mg/L), diesel fuel (0.17 mg/L), military jet fuel JP-4 (1.57 mg/L) (Potter, 1996), new motor oil (0.15 to 0.17 µg/L), and used motor oil (117 to 124 µg/L) (Chen et al., 1994). The average volume percent and estimated mole fraction in American Petroleum Institute PS-6 gasoline are 1.570 and 0.017, respectively (Poulsen et al., 1992). Diesel fuel obtained from a service station in Schlieren, Switzerland contained ethylbenzene at a concentration of 690 mg/L (Schluep et al., 2001). Kaplan et al. (1996) determined ethylbenzene concentrations in four different grades of gasolines. Average ethylbenzene concentrations were 9.1 g/L in regular unleaded gasoline, 8.0 g/L in leaded gasoline, 9.3 g/L in unleaded plus gasoline, and 10.1 g/L in Super unleaded gasoline. Thomas and Delfino (1991) equilibrated contaminant-free groundwater collected from Gainesville, FL with individual fractions of three individual petroleum products at 24-25 °C for 24 h. The aqueous phase was analyzed for organic compounds via U.S. EPA approved test method 602. Average ethylbenzene concentrations reported in water-soluble fractions of unleaded gasoline, kerosene, and diesel fuel were 2.025, 0.314, and 0.104 mg/L, respectively. When the authors analyzed the aqueous-phase via U.S. EPA approved test method 610, average ethylbenzene concentrations in water-soluble fractions of unleaded gasoline, kerosene, and diesel fuel were lower, i.e., 1.423, 0.171, and 0.079 mg/L, respectively. Schauer et al. (1999) reported ethylbenzene in a diesel-powered medium-duty truck exhaust at an emission rate of 470 µg/km. California Phase II reformulated gasoline contained ethylbenzene at a concentration of 12,800 mg/kg. Gas-phase tailpipe emission rates from gasoline-powered automobiles with and without catalytic converters were 4.18 and 434.0 mg/km, respectively (Schauer et al., 2002). Detected in 1-yr aged coal tar film and bulk coal tar at concentrations of 350 and 2,100 mg/kg, respectively (Nelson et al., 1996). A high-temperature coal tar contained ethylbenzene at an average concentration of 0.02 wt % (McNeil, 1983). Identified as one of 140 volatile constituents in used soybean oils collected from a processing plant that fried various beef, chicken, and veal products (Takeoka et al., 1996). Schauer et al. (2001) measured organic compound emission rates for volatile organic compounds, gas-phase semi-volatile organic compounds, and particle-phase organic compounds from the residential (fireplace) combustion of pine, oak, and eucalyptus. The gas-phase emission rate of ethylbenzene was 22.9 mg/kg of pine burned. Emission rates of ethylbenzene were not measured during the combustion of oak and eucalyptus. Uses: Intermediate in production of styrene, acetophenone, ethylcyclohexane, benzoic acid, 1bromo-1-phenylethane, 1-chloro-1-phenylethane, 2-chloro-1-phenylethane, p-chloroethylbenzene, p-chlorostyrene, and many other compounds; solvent; in organic synthesis.