p-XYLENE

CH3 Note: According to Chevron Phillips Company’s (2006) Technical Data Sheet, >99.7 wt % pxylene typically contains toluene (≤ 0.10 wt %), o-xylene (≤ 0.10 wt %), m-xylene (≤ 0.20 wt %), ethyl-benzene (≤ 0.20 wt %), and nonaromatic hydrocarbons (≤ 0.20 wt %). CASRN: 106-42-3; DOT: 1307; DOT label: Flammable liquid; molecular formula: C8H10; FW: 106.17; RTECS: ZE2625000; Merck Index: 12, 10214 Physical state, color, and odor: Clear, colorless, watery liquid with a sweet odor. Odor threshold concentrations reported in air were 47 ppbv by Leonardos et al. (1969) and 58 ppbv by Nagata and Takeuchi (1990). Melting point (°C): 13.50 (Martin et al., 1979) Boiling point (°C): 138.38 (Tu et al., 2001) Density (g/cm3): 0.8653 at 15 °C, 0.8612 at 20 °C, 0.8566 at 25 °C, 0.8521 at 30 °C, 0.8478 at 35 °C (Konti et al.,

1997) 0.86314 at 20.00 °C (Tsierkezos et al., 2000) 0.85655 at 25.00 °C (Lores et al., 1999) 0.85228 at 35.00 °C (Goud et al., 1999) Diffusivity in water (x 10-5 cm2/sec): 0.79 at 20 °C using method of Hayduk and Laudie (1974) Dissociation constant, pKa: >15 (Christensen et al., 1975) Flash point (°C): 27 (NIOSH, 1997) Lower explosive limit (%): 1.1 (NIOSH, 1997) Upper explosive limit (%): 7.0 (NIOSH, 1997) Entropy of fusion (cal/mol⋅K): 14.28 (Pitzer and Scott, 1941; Corruccini and Ginnings, 1947)

14.13 (Huffman et al., 1930) Heat of fusion (kcal/mol): 4.047 (Huffman et al., 1930) 4.090 (Pitzer and Scott, 1941) 4.087 (Corruccini and Ginnings, 1947) 4.091 (Messerly et al., 1988) Henry’s law constant (x 10-3 atm⋅m3/mol): 2.46 at 20 °C (batch equilibrium, Gan and Dupont, 1989) 5.712 at 22 °C (SPME-GC, Saraullo et al., 1997) 7.1 (Pankow and Rosen, 1988) 7.68 (Tuazon et al., 1986a) 4.20, 4.83, 6.45, 7.44, and 9.45 at 10, 15, 20, 25, and 30 °C, respectively (EPICS, Ashworth et al.,

1988) 4.35 (Wasik and Tsang, 1970) Distilled water: 1.89, 1.67, 2.62, 4.73, and 5.68 at 2.0, 6.0, 10.0, 18.2, and 25.0 °C, respectively;

natural seawater: 3.13 and 7.53 at 6.0 and 25.0 °C, respectively (EPICS, Dewulf et al., 1995) 16.1 at 45.00 °C, 18.6 at 50.00 °C, 20.3 at 55.00 °C, 23.4 at 60.00 °C, 30.5 at 70.00 °C (static

headspace-GC, Park et al., 2004) Interfacial tension with water (dyn/cm at 20 °C): 37.77 (Harkins et al., 1920) Ionization potential (eV): 8.44 (Franklin et al., 1969) Soil organic carbon/water partition coefficient, log Koc: 2.31 (Abdul et al., 1987) 2.42 (estuarine sediment, Vowles and Mantoura, 1987) 2.72 (Captina silt loam), 2.87 (McLaurin sandy loam) (Walton et al., 1992) 2.52 (Schwarzenbach and Westall, 1984) 2.49, 2.75, 2.65, 2.76, 2.79, 2.77, and 2.78 at 2.3, 3.8, 6.2, 8.0, 13.5, 18.6, and 25.0 °C,

respectively, for a Leie River (Belgium) clay (Dewulf et al., 1999a) Bioconcentration factor, log BCF: 1.37 (eels, Ogata and Miyake, 1978) 1.17 (goldfish, Ogata et al., 1984) 2.41 (Selenastrum capricornutum, Herman et al., 1991) Octanol/water partition coefficient, log Kow: 3.18 at 25.0 °C (generator column-HPLC, Tewari et al., 1982; generator column-HPLC/GC,

Wasik et al., 1981, 1983) 3.20 (generator column-HPLC/GC, Wasik et al., 1981) 3.12 (shake flask-GC, Jaynes and Vance, 1996) 3.29 (generator column-HPLC, Garst, 1984) 3.65 (estimated from HPLC capacity factors, Eadsforth, 1986) Solubility in organics: Soluble in acetone, ethanol, and benzene (Weast, 1986)

200 mg/L solution at 25 °C (shake flask-UV spectrophotometry, Andrews and Keefer, 1949) 2.02 mM at 25.0 °C (generator column-HPLC, Tewari et al., 1982; generator column-HPLC/GC,

Wasik et al., 1981, 1983) 1.63 mM at 25 °C (headspace analysis, Keeley et al., 1991) In mg/L: 156 at 0.4 °C, 188 at 10.0 °C, 195 at 14.9 °C, 197 at 21.0 °C, 198 at 25.0 °C, 199 at 25.6 °C, 201 at 30.2 °C, 204 at 30.3 °C, 207 at 34.9 °C, 207 at 35.2 °C, 222 at 42.8 °C (shake flaskUV spectrophotometry, Bohon and Claussen, 1951)

185 mg/kg at 25 °C (shake flask-GC, Polak and Lu, 1973) 156.0 mg/L at 25.0 °C in distilled water, 110.9 mg/L in artificial seawater at 25.0 °C (shake flask-

GC, Sutton and Calder, 1975) 163.3 mg/L at 25 °C (Hermann, 1972) 1.94 mM at 35 °C (Hine et al., 1963) 1.48, 1.53, 1.61, and 1.66 mM at 15, 25, 35, and 45 °C, respectively (Sanemasa et al., 1982) 0.019 wt % at 25 °C (shake flask-radiometry, Lo et al., 1986) 157.0 mg/kg at 25 °C (shake flask-GLC, Price, 1976) In wt % (°C): 0.049 (141), 0.096 (169), 0.231 (194), 0.607 (231), 1.283 (258) (Guseva and

Parnov, 1963) In mg/kg: 186 at 10 °C, 196 at 20 °C, 200 at 30 °C (shake flask-UV spectrophotometry, Howe et

al., 1987) 1.51 mM at 25.0 °C (Sanemasa et al., 1987) 3.00 x 10-5 at 25 °C (mole fraction, inert gas stripping-GC, Li et al., 1993) 256.4 mg/kg at 43.0 °C, 300.7 mg/kg at 56.4 °C, 339.5 mg/kg at 65.0 °C, 387.3 at 75.3 °C, 607.8

mg/kg at 87.2 °C (ampoules-cloud point, Pryor and Jentoft, 1961) Vapor density: 4.34 g/L at 25 °C, 3.66 (air = 1) Vapor pressure (mmHg): 2.3 at 10 °C, 10.7 at 30 °C, 32.3 at 30 °C (Rintelen et al., 1937) 1.56 at 0 °C, 3.11 at 10 °C, 5.90 at 20 °C, 10.7 at 30 °C, 18.4 at 40 °C, 30.7 at 50 °C, 49.3 at 60 °C, 76.7 at 70 °C, 115.9 at 80 °C (cathetometry, Kassel, 1936)

8.8 at 25 °C (quoted, Mackay et al., 1982) 15.8 at 35 °C (Hine et al., 1963) 19.9 at 40.00 °C (static method, Asmanova and Goral, 1980) 4.363 at 13.285 °C, 4.867 at 15.004 °C, 5.666 at 17.474 °C, 6.603 at 20.015 °C (inclined-piston,

Osborn and Douslin, 1974) Environmental fate: Biological. Microbial degradation of p-xylene produced 4-methylbenzyl alcohol, pmethylbenzaldehyde, p-toluic acid, and 4-methylcatechol (quoted, Verschueren, 1983). Dimethylcis,cis-muconic acid, and 2,3-dihydroxy-p-toluic acid were reported to be biooxidation products of p-xylene by Nocardia corallina V-49 using n-hexadecane as the substrate (Keck et al., 1989). Reported biodegradation products of the commercial product containing xylene include α-hydroxy-p-toluic acid, p-methylbenzyl alcohol, benzyl alcohol, 4-methylcatechol, m-and ptoluic acids (Fishbein, 1985). It was reported that p-xylene was cometabolized resulting in the formation of p-toluic and 2,3-dihydroxy-o-toluic acids (Pitter and Chudoba, 1990). In anoxic groundwater near Bemidji, MI, p-xylene anaerobically biodegraded to the intermediate p-toluic acid (Cozzarelli et al., 1990). In gasoline-contaminated groundwater, methylbenzylsuccinic acid was identified as the first intermediate during the anaerobic degradation of xylenes (Reusser and Field, 2002).