CHLOROBENZENE

Note: Commercial grades of chlorobenzene may contain minor quantities of benzene (<0.05 wt %) and dichlorobenzenes (0.1 wt %). CASRN: 108-90-7; DOT: 1134; DOT label: Flammable liquid; molecular formula: C6H5Cl; FW: 112.56; RTECS: CZ0175000; Merck Index: 12, 2172 Physical state, color, and odor: Clear, colorless, flammable liquid with a sweet almond, medicinal or mothball-like odor. An odor threshold concentration of 210 ppbv was reported by Leonardos et al. (1969). At 40 °C, the lowest concentration at which an odor was detected was 190 µg/L. At 25 °C, the lowest concentration at which a taste was detected was 190 µg/L (Young et al., 1996). The average least detectable odor threshold concentration in water at 60 °C was 0.08 mg/L (Alexander et al., 1982). Cometto-Muñiz and Cain (1994) reported an average nasal pungency threshold concentration of 10,553 ppmv. Melting point (°C): -45.6 (Weast, 1986) Boiling point (°C): 131.7 (Artigas et al., 1997) Density (g/cm3): 1.10646 at 20.00 °C (Tsierkezos et al., 2000) 1.10101 at 25.00 °C (Dejoz et al., 1997) 1.09547 at 30.00 °C (Ramadevi et al., 1996) 1.0904 at 35.00 °C, 1.0790 at 45.00 °C (Sastry et al., 1999) 1.08498 at 40 °C (Kalali et al., 1992) Diffusivity in water (x 10-5 cm2/sec): At 25 °C: 1.04 (x = 2 x 10-6), 1.00 (x = 4 x 10-6), 0.98 (x = 8 x 10-6) (Gabler et al., 1996) Flash point (°C): 27.8 (NIOSH, 1997) Lower explosive limit (%): 1.3 (NIOSH, 1997) Upper explosive limit (%): 9.6 (NIOSH, 1997) Entropy of fusion (cal/mol⋅K): 10.02 (Stull, 1937)

2.28 (Dean, 1987) Henry’s law constant (x 10-3 atm⋅m3/mol): 3.93 at 25 °C (gas stripping-UV spectrophotometry, Warner et al., 1987) 3.67 at 25 °C (static headspace-GC, Welke et al., 1998) 3.6 (Pankow and Rosen, 1988) 3.70 at 25 °C (gas stripping-UV spectrophotometry, Mackay et al., 1979) 6.21 at 37 °C (Sato and Nakajima, 1979) 2.44, 2.81, 3.41, 3.60, and 4.73 at 10, 15, 20, 25, and 30 °C, respectively (EPICS, Ashworth et al.,

1988) 2.84 at 20.00 °C (inert gas stripping, Hovorka and Dohnal, 1997) 3.11 at 25 °C (gas stripping-GC, Shiu and Mackay, 1997) 3.85 at 25 °C (Hoff et al., 1993) 3.30 at 25.0 °C (mole fraction ratio-GC, Leighton and Calo, 1981) 3.38 at 25.0 °C (Ramachandran et al., 1996) 1.11, 1.54, 1.81, 2.80, and 3.79 at 2.0, 6.0, 10.0, 18.0, and 25.0 °C, respectively (EPICS-SPME,

Dewulf et al., 1999) Interfacial tension with water (dyn/cm): 37.41 at 20 °C (Harkins et al., 1920) 38.10 at 20 °C, 37.22 at 40 °C, 35.80 at 60 °C, 33.83 at 80 °C (Jasper and Seitz, 1959) Ionization potential (eV): 9.07 (Lias, 1998) 9.14 (quoted, Yoshida et al., 1983) Bioconcentration factor, log BCF: 3.23 (activated sludge), 1.70 (algae), 1.88 (golden ide) (Freitag et al., 1985) 2.65 (fathead minnow, Veith et al., 1979) 3.69 green alga, Selenastrum capricornutum (Casserly et al., 1983) Soil organic carbon/water partition coefficient, log Koc: 1.92 (Woodburn silt loam, Chiou et al., 1983) 2.07 (Lincoln sand, Wilson et al., 1981) 2.59 (Roberts et al., 1980) 1.91 (Mt. Lemmon soil, Hu et al., 1995) 2.50 (Captina silt loam), 2.17 (McLaurin sandy loam) (Walton et al., 1992) 2.22 (field sample), 2.41 (average of 6 measurements), 2.70 (field sample) (Schwarzenbach and

Westall, 1981) 2.37 (sandy soil, Van Gestel and Ma, 1993) 2.10 (muck), 1.89 (Eustis sand) (Brusseau et al., 1990) 2.30 (sewage solids, Dobbs et al., 1989) 2.58 (Calvert silt loam, Xia and Ball, 1999) Octanol/water partition coefficient, log Kow: 2.84 at 25 °C (shake flask-UV spectrophotometry, Fujita et al., 1964; Mirrlees et al., 1976; RP-

HPLC, Garst and Wilson, 1984; shake flask-GC, Pereira et al., 1988) 2.81 (Mirrlees et al., 1976) 2.98 (generator column-HPLC, Tewari et al., 1982; generator column-HPLC/GC, Wasik et al.,

1981, 1983; generator column, Doucette and Andren, 1988; Paschke et al., 1998)

2.898 at 25 °C (shake flask-GLC, de Bruijn et al., 1989; Brooke et al., 1990) 2.96 at 25 °C (dialysis-HPLC, Andersson and Schräder, 1999) 2.784 and 2.898 at 25 °C (shake flask-HPLC, Brooke et al., 1990) 2.83 (estimated from HPLC capacity factors, Hammers et al., 1982) 2.65 (Campbell and Luthy, 1985) 2.88 at 25 °C (modified shake-flask-UV spectrophotometry, Sanemasa et al., 1994) Solubility in organics: Soluble in ethanol, benzene, carbon tetrachloride, chloroform, ether, and methylene chloride Solubility in water: 502 mg/L at 25 °C (shake flask-HPLC, Banerjee, 1984) 333 mg/L at 25 °C (shake flask-GC, Boyd et al., 1998) 295 mg/L at 25.0 °C (generator column-HPLC, Tewari et al., 1982; generator column-HPLC/GC,

Wasik et al., 1981) 4.43 mM at 25 °C (generator column-HPLC, Wasik et al., 1983) 471.7 mg/L at 25 °C (shake flask-GC, Aquan-Yuen et al., 1979) 500 mg/L at 25 °C (shake flask-UV spectrophotometry, Andrews and Keefer, 1950) 488 mg/kg at 30 °C (shake flask-interferometer, Gross and Saylor, 1931) 448 mg/L at 30 °C (Freed et al., 1977) 503 mg/L at 25 °C (shake flask-UV spectrophotometry, Yalkowsky et al., 1979) 534 mg/kg at 21 °C (shake flask-GC, Chey and Calder, 1972) 474.0 mg/L at 30 °C (vapor equilibrium-GC, McNally and Grob, 1983, 1984) 0.035 wt % at 25 °C (shake flask-radiometry, Lo et al., 1986) 4.11 mmol/kg at 25.0 °C (shake flask-UV spectrophotometry, Vesala, 1974) 3.78 mM at 25.0 °C (Sanemasa et al., 1987) 496 mg/L at 25 °C (generator column-GC, Paschke et al., 1998) 0.046, 0.045, and 0.050 wt % at 10.0, 20.0, and 30.0 °C, respectively (Schwarz and Miller, 1980) 496 mg/L at 5.0 °C, 429 mg/L at 15.0 °C, 470 mg/L at 25.0 °C, 538 mg/L at 35.0 °C, 546 mg/L at

45.0 °C (shake flask-GC, Ma et al., 2001) In mg/kg: 411 at 10 °C, 441 at 20 °C, 464 at 30 °C (shake flask-UV spectrophotometry, Howe et al., 1987) Vapor density: 4.60 g/L at 25 °C, 3.88 (air = 1) Vapor pressure (mmHg): 9.1 at 20 °C (Wahid, 1993) 11.86 at 25 °C (quoted, Mackay et al., 1982) 15.8 at 30.00 °C, 43.8 at 50 °C (Kalali et al., 1992) 212 at 90.00 °C (Harris et al., 2003) Environmental fate: Biological. In activated sludge, 31.5% of the applied chlorobenzene mineralized to carbon dioxide after 5 d (Freitag et al., 1985). A mixed culture of soil bacteria or a Pseudomonas sp. transformed chlorobenzene to chlorophenol (Ballschiter and Scholz, 1980). Pure microbial cultures isolated from soil hydroxylated chlorobenzene to 2-and 4-chlorophenol (Smith and Rosazza, 1974). Chlorobenzene was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum. At a concentration of 5 mg/L, biodegradation yields at the end of 1 and 2 wk were 89 and 100%, respectively. At a concentration of 10 mg/L, significant

after the 3rd week of incubation (Tabak et al., 1981). Heukelekian and Rand (1955) reported a 5-d BOD value of 0.03 g/g which is 1.5% of the ThOD value of 2.00 g/g. Surface Water. Estimated half-lives of chlorobenzene (1.0 µg/L) from an experimental marine mesocosm during the spring (8-16 °C), summer (20-22 °C), and winter (3-7 °C) were 21, 4.6, and 13 d, respectively (Wakeham et al., 1983). Photolytic. Under artificial sunlight, river water containing 2-5 ppm chlorobenzene degraded to phenol and chlorophenol. The lifetimes of chlorobenzene in distilled water and river water were 17.5 and 3.8 h, respectively (Mansour et al., 1989). In distilled water containing 1% acetonitrile exposed to artificial sunlight, 28% of chlorobenzene photolyzed to phenol, chloride ion, and acetanilide with reported product yields of 55, 112, and 2%, respectively (Dulin et al., 1986). Titanium dioxide suspended in an aqueous solution and irradiated with UV light (λ = 365 nm) converted chlorobenzene to carbon dioxide at a significant rate (Matthews, 1986). Products identified as intermediates in this reaction include three monochlorophenols, chlorohydroquinone, and hydroxyhydroquinone (Kawaguchi and Furuya, 1990). Photooxidation of chlorobenzene in air containing nitric oxide in a Pyrex glass vessel and a quartz vessel gave 3-chloronitrobenzene, 2-chloro-6-nitrophenol, 2-chloro-4-nitrophenol, 4chloro-2-nitro-phenol, 4-nitrophenol, 3-chloro-4-nitrophenol, 3-chloro-6-nitrophenol, and 3chloro-2-nitrophenol (Kanno and Nojima, 1979). A carbon dioxide yield of 18.5% was achieved when chlorobenzene adsorbed on silica gel was irradiated with light (λ >290 nm) for 17 h. The sunlight irradiation of chlorobenzene (20 g) in a 100-mL borosilicate glass-stoppered Erlenmeyer flask for 28 d yielded 1,060 ppm monochlorobiphenyl (Uyeta et al., 1976). When an aqueous solution containing chlorobenzene (190 µM) and a nonionic surfactant micelle (Brij 58, a polyoxyethylene cetyl ether) was illuminated by a photoreactor equipped with 253.7-nm monochromatic UV lamps, phenol, hydrogen, and chloride ions formed as major products. It was reported that aromatic aldehydes, organic acids, and carbon dioxide would form from the photoreaction of chlorobenzene in water under similar conditions. A duplicate experiment was conducted using an ionic micelle (triethylamine, 5 mM), which serves as a hydrogen source. Products identified were phenol and benzene (Chu and Jafvert, 1994). Chemical/Physical. Anticipated products from the reaction of chlorobenzene with ozone or OH radicals in the atmosphere are chlorophenols and ring cleavage compounds (Atkinson et al., 1985; Cupitt, 1980). In the absence of oxygen, chlorobenzene reacted with Fenton’s reagent forming chlorophenols, dichlorobiphenyls, and phenolic polymers as major intermediates. With oxygen, chlorobenzoquinone, chlorinated and nonchlorinated diols formed (Sedlak and Andren, 1991). Augusti et al. (1998) conducted kinetic studies for the reaction of chlorobenzene (0.2 mM) and other monocyclic aromatics with Fenton’s reagent (8 mM hydrogen peroxide; [Fe+2] = 0.1 mM) at 25 °C. They reported a reaction rate constant of 0.0820/min. The following intermediates were identified during this reaction: chlorophenol, chlorohydroquinone, chloroquinone, hydroquinone, and quinone. Based on an assumed base mediated 1% disappearance after 16 d at 85 °C and pH 9.70 (pH 11.26 at 25 °C), the hydrolysis half-life of chlorobenzene was estimated to be >900 yr (Ellington et al., 1988). Toxic fumes of phosgene and hydrogen chloride may form when exposed to an open flame (CHRIS, 1984). Chlorobenzene is stable up to 700 °C but in combination with other chlorinated compounds, it is stable up to 900 °C (Graham et al., 1986). At influent concentrations of 10.0, 1.0, 0.1, and 0.01 mg/L, the adsorption capacity of the GAC used at pH 7.4 were 890, 91, 9.3, and 0.95 mg/g, respectively (Dobbs and Cohen, 1980). Exposure limits: NIOSH REL: Awaiting OSHA ruling to determine if the recommended TWA

ppm (350 mg/m3); ACGIH TLV: TWA 10 ppm (adopted). Symptoms of exposure: Inhalation of vapors may cause drowsiness, incoordination, and liver damage. May irritate eyes and skin (Patnaik, 1992). An irritation concentration of 933.33 mg/m3 in air was reported by Ruth (1986). Toxicity: EC50 (96-h) and EC50 (3-h) concentrations that inhibit the growth of 50% of Selenastrum capricornutum population are 12.5 and 33.0 mg/L, respectively (Calamari et al., 1983). EC50 (48-h) for Daphnia magna 3.60 mg/L (Marchini et al., 1999), Pseudokirchneriella subcapitata 11.68 mg/L (Hsieh et al., 2006). EC50 (3-h) for Selenastrum capricornutum 33.0 mg/L (Calamari et al., 1983). LC50 (contact) for earthworm (Eisenia fetida) 29 µg/cm2 (Neuhauser et al., 1985). LC50 for goldfish 1.8 mL/kg (quoted, Verschueren, 1983), 89.7 and 164 mg/L (soil porewater concentration) for earthworm (Eisenia andrei) and 252 and 482 mg/L (soil porewater concentration) for earthworm (Lumbricus rubellus) (Van Gestel and Ma, 1993). LC50 for male rats 13,490 mg/m3 (Bonnet et al., 1982), female mice 8,581 mg/m3 (Bonnet et al., 1979). LC50 (14-d) for Poecilia reticulata 19.1 mg/L (Könemann, 1981). LC50 (7-d) for Micropterus salmoides 50 mg/L (Birge et al., 1979). LC50 (96-h) for bluegill sunfish 16 mg/L (Spehar et al., 1982). LC50 (96-h static flow-through system) for Oncorhynchus mykiss 7.36 mg/L (Hodson et al., 1984), 4.7 mg/L (Dalich et al., 1982), Cyprinodon variegatus 10 ppm using natural seawater (Heitmuller et al., 1981). LC50 (48-h) for Daphnia magna 86 mg/L (LeBlanc, 1980), Cyprinodon variegatus 8.9 ppm (Heitmuller et al., 1981). LC50 (24-h) for Daphnia magna 140 mg/L (LeBlanc, 1980), Cyprinodon variegatus >20 ppm (Heitmuller et al., 1981). Acute oral LD50 for rats 2,910 mg/kg, guinea pigs 5,060 mg/kg, rabbits 2,250 mg/kg (quoted, RTECS, 1985). Drinking water standard (final): MCLG: 0.1 mg/L; MCL: 0.1 mg/L. In addition, a DWEL of 700 µg/L was recommended (U.S. EPA, 2000). Uses: Preparation of phenol, 4-chlorophenol, chloronitrobenzene, aniline, 2-, 3-, and 4-nitrochlorobenzenes; carrier solvent for methylene diisocyanate and pesticides; solvent for paints; insecticide, pesticide, and dyestuffs intermediate; heat transfer agent.