ISOPROPYLBENZENE

CASRN: 98-82-8; DOT: 1918; molecular formula: C9H12; FW: 120.19; RTECS: GR8575000; Merck Index: 12, 2683 Physical state, color, and odor: Colorless liquid with an aromatic odor. Experimentally determined detection and recognition odor threshold concentrations were 40 µg/m3 (8 ppbv) and 230 µg/m3 (47 ppbv), respectively (Hellman and Small, 1974). The taste threshold concentration in water is 60 ppb (Young et al., 1996). Melting point (°C): -96 (Weast, 1986) -96.8 (quoted, Mackay et al., 1982) Boiling point (°C): 152.4 (Weast, 1986) Density (g/cm3): 0.8618 at 20 °C (Weast, 1986) Diffusivity in water (x 10-5 cm2/sec): 0.73 at 20 °C using method of Hayduk and Laudie (1974) Dissociation constant, pKa: >14 (Schwarzenbach et al., 1993) Flash point (°C): 39 (Windholz et al., 1983) 36 (NIOSH, 1997) Lower explosive limit (%): 0.9 (NIOSH, 1997) Upper explosive limit (%): 6.5 (NIOSH, 1997) 8.8 (Butler and Webb, 1957) Heat of fusion (kcal/mol): 1.86 (Dean, 1987) Henry’s law constant (x 10-3 atm⋅m3/mol): 3.51, 4.20, 5.03, 5.58, and 7.70 at 10, 15, 20, 25, and 30 °C, respectively (EPICS, Ashworth et al.,

Interfacial tension with water (dyn/cm): At pH 7: 32.4, 32.3, 32.2, and 32.1 at 20, 25, 30, and 40 °C, respectively (Saien and Aghababaei,

2005) Ionization potential (eV): 9.13 (quoted, Yoshida et al., 1983) 8.75 (NIOSH, 1997) Bioconcentration factor, log BCF: 1.55 (goldfish, Ogata et al., 1984) Soil organic carbon/water partition coefficient, log Koc: 3.45 using method of Karickhoff et al. (1979) 3.40 (estimated, Ellington et al., 1993) Octanol/water partition coefficient, log Kow: 3.63 (Chiou et al., 1977, 1982) 3.66 (quoted, Leo et al., 1971) Solubility in organics: Soluble in acetone, alcohol, benzene, and ether (Weast, 1986) Solubility in water: 48.3 mg/kg at 25 °C (shake flask-GLC, Price, 1976) 50.5 mg/kg at 25 °C (shake flask-GC, McAuliffe, 1966) 53 mg/kg at 25 °C (shake flask-GC, McAuliffe, 1963) 65.3 mg/L in distilled water at 25.0 °C, 42.5 mg/L in seawater at 25.0 °C (shake flask-GC, Sutton

and Calder, 1975). 73 mg/L solution at 25.0 °C (shake flask-UV spectrophotometry, Andrews and Keefer, 1950a) 0.299 mM in 0.5 M NaCl at 25 °C (Wasik et al., 1984) 495, 510, 568, and 638 µM at 15, 25, 35, and 45 °C, respectively (Sanemasa et al., 1982) 500 mg/L in artificial seawater at 25 °C (Price et al., 1974) In mole fraction (x 10-5): 1.2050 at 24.94 °C, 1.2416 at 29.98 °C, 1.2825 at 34.92 °C, 1.3446 at

39.96 °C, 1.4162 at 44.91 °C, 1.5037 at 49.90 °C, 1.6011 at 54.92 °C, 1.7221 at 59.98 °C, 1.8624 at 65.17 °C, 2.0302 at 70.32 °C, 2.2064 at 75.10 °C, 2.4212 at 80.21 °C (continuous circulation cell-UV spectrophotometry, Glew and Robertson, 1956)

170 mg/kg at 25 °C (shake flask-turbidimetric, Stearns et al., 1947) 9.80 x 10-6 at 25 °C (mole fraction, inert gas stripping-GC, Li et al., 1993) Vapor density: 4.91 g/L at 25 °C, 4.15 (air = 1) Vapor pressure (mmHg): 3.2 at 20 °C (quoted, Verschueren, 1983) 4.6 at 25 °C (quoted, Mackay et al., 1982) Environmental fate: Biological. When isopropylbenzene was incubated with Pseudomonas putida, the substrate was

intact (Gibson, 1968). Oxidation of isopropylbenzene by Pseudomonas desmolytica S44B1 and Pseudomonas convexa S107B1 yielded 3-isopropylcatechol and a ring fission product, (+)-2hydroxy-7-methyl-6-oxooctanoic acid (Jigami et al., 1975). Surface Water. Mackay and Wolkoff (1973) estimated an evaporation half-life of 14.2 min from a surface water body that is 25 °C and 1 m deep. Photolytic. Major products reported from the photooxidation of isopropylbenzene with nitrogen oxides include nitric acid and benzaldehyde (Altshuller, 1983). A n-hexane solution containing isopropylbenzene and spread as a thin film (4 mm) on cold water (10 °C) was irradiated by a mercury medium pressure lamp. In 3 h, 22% of the applied isopropylbenzene photooxidized into α,α-dimethylbenzyl alcohol, 2-phenylpropionaldehyde, and allylbenzene (Moza and Feicht, 1989). A rate constant of 3.7 x 109 L/molecule·sec was reported for the reaction of isopropylbenzene with OH radicals in the gas phase (Darnall et al., 1976). Similarly, a room temperature rate constant of 6.6 x 10-12 cm3/molecule·sec was reported for the vapor-phase reaction of isopropylbenzene with OH radicals (Atkinson, 1985). At 25 °C, a rate constant of 6.25 x 10-12 cm3/molecule·sec was reported for the same reaction (Ohta and Ohyama, 1985). Chemical/Physical. Complete combustion in air yields carbon dioxide and water vapor. Isopropylbenzene will not hydrolyze because it does not contain a hydrolyzable functional group. The calculated evaporation half-life of isopropylbenzene from surface water 1 m deep at 25 °C is 5.79 h (Mackay and Leinonen, 1975). Exposure limits: NIOSH REL: TWA 50 ppm (245 mg/m3), IDLH 900 ppm; OSHA PEL: TWA 50 ppm; ACGIH TLV: TWA 50 ppm (adopted). Symptoms of exposure: Vapors may cause irritation to the eyes, skin, and upper respiratory system. Narcotic at high concentrations (Patnaik, 1992). Toxicity: EC50 (72-h) for Selenastrum capricornutum 2.6 mg/L (Galassi et al., 1988). LC50 (96-h) for Salmo gairdneri 2.7 mg/L, Poecilia reticulata 5.1 mg/L (Galassi et al., 1988). Acute oral LD50 for rats 1,400 mg/kg (quoted, RTECS, 1985). Drinking water standard: As of October 1995, no MCLGs or MCLs have been proposed although isopropylbenzene has been listed for regulation (U.S. EPA, 1996). A DWEL of 400 µg/L was recommended (U.S. EPA, 2000). Source: Detected in distilled water-soluble fractions of 94 octane gasoline and Gasohol at concentrations of 0.14 and 0.15 mg/L, respectively (Potter, 1996). 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 isopropylbenzene concentrations reported in water-soluble fractions of unleaded gasoline and kerosene were 235 and 28 µg/L, respectively. When the authors analyzed the aqueous-phase via U.S. EPA approved test method 610, average isopropylbenzene concentrations in water-soluble fractions of unleaded gasoline and kerosene were lower, i.e., 206 and 22 µg/L, respectively. Isopropylbenzene was detected in both water-soluble fractions of diesel fuel but were not quantified. Isopropylbenzene was detected in California Phase II reformulated gasoline at a concentration of 830 mg/kg (Schauer et al., 2002).