ABSTRACT

CH3 CASRN: 95-63-6; DOT: 2325; DOT label: Combustible liquid; molecular formula: C9H12; FW: 120.19; RTECS: DC3325000; Merck Index: 12, 8100 Physical state, color, and odor: Colorless liquid with a slight aromatic odor. A detection odor threshold concentration of 12 mg/m3 (2.4 ppmv) was experimentally determined by Dravnieks (1974). Melting point (°C): -43.8 (Weast, 1986) Boiling point (°C): 169.3 (Weast, 1986) Density (g/cm3): 0.8758 at 20 °C (Weast, 1986) 0.87164 at 25.00 °C, 0.85950 at 30.00 °C (Deng et al., 2006) 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): 54.4 (Sax and Lewis, 1987) 44 (NFPA, 1984) Lower explosive limit (%): 0.9 (NFPA, 1984) Upper explosive limit (%): 6.4 (NFPA, 1984) Entropy of fusion (cal/mol⋅K): 13.2 (Huffman et al., 1931) Heat of fusion (kcal/mol): 3.023 (Huffman et al., 1931) Henry’s law constant (x 10-3 atm⋅m3/mol): 6.946, 11.202, and 15.702 at 27.0, 35.0, and 45.0 °C, respectively (dynamic headspace, Hansen et al., 1995)

8.27 (Lias, 1998) Bioconcentration factor, log BCF: 2.90, 3.26, 3.18, 3.95, 5.04, and 4.72 for olive, grass, holly, ivy, mock orange, pine, and rosemary, respectively (Hiatt, 1998) Soil organic carbon/water partition coefficient, log Koc: 3.57 using method of Karickhoff et al. (1979) Octanol/water partition coefficient, log Kow: 3.55 at 25.0 °C (generator column-HPLC, Tewari et al., 1982) 3.63 (generator column, Doucette and Andren, 1988) 3.65 (Mackay et al., 1980) 3.78 (Camilleri et al., 1988; estimated from HPLC capacity factors, Hammers et al., 1982) Solubility in organics: Soluble in acetone, alcohol, benzene, and ether (Weast, 1986) Solubility in water: 51.9 mg/kg at 25 °C (shake flask-GLC, Price, 1976) 57 mg/kg at 25 °C (shake flask-GC, McAuliffe, 1966) 59.0 mg/L at 25.0 °C (shake flask-GC, Sutton and Calder, 1975) 0.313 mM in 0.5 M NaCl at 25 °C (Wasik et al., 1984) 435, 469, 514, and 571 µM at 15.0, 25.0, 35.0, and 45.0 °C, respectively (Sanemasa et al., 1982) 3.47 mg/L (water soluble fraction of a 15-component simulated jet fuel mixture (JP-8) containing

6.9 wt % 1,2,4-trimethylbenzene, MacIntyre and deFur, 1985) Vapor density: 4.91 g/L at 25 °C, 4.15 (air = 1) Vapor pressure (mmHg): 2.03 at 25 °C (quoted, Mackay et al., 1982) Environmental fate: Biological. In anoxic groundwater near Bemidji, MI, 1,2,4-trimethylbenzene anaerobically biodegraded to the intermediate 3,4-dimethylbenzoic acid and the tentatively identified compounds 2,4-and/or 2,5-dimethylbenzoic acid (Cozzarelli et al., 1990). Photolytic. Glyoxal, methylglyoxal, and biacetyl were produced from the photooxidation of 1,2,4-trimethylbenzene by OH radicals in air at 25 °C (Tuazon et al., 1986a). A rate constant of 2.0 x 10-8 L/molecule⋅sec was reported for the reaction of 1,2,4-trimethylbenzene with OH radicals in the gas phase (Darnall et al., 1976). Similarly, the rate constants for the reaction of 1,2,4trimethylbenzene and OH radicals at room temperature were 3.35 x 10-11 (Hansen et al., 1975) and 3.84 x 10-11 cm3/molecule⋅sec (Atkinson, 1985). At 25 °C, a rate constant of 3.15 x 10-11 cm3/molecule⋅sec was reported for the same reaction (Ohta and Ohyama, 1985). Products identified from the OH radical-initiated reaction of 1,2,4-trimethylbenzene in the presence of nitrogen dioxide were 3-hexene-2,5-dione and 2,3-butanedione (Bethel et al., 2000). Chemical/Physical. 1,2,4-Trimethylbenzene will not hydrolyze in water (Kollig, 1993). Exposure limits: NIOSH REL: TWA 25 ppm (125 mg/m3); ACGIH TLV: TWA for mixed isomers 25 ppm (adopted).