4-METHYLPHENOL

CH3 CASRN: 106-44-5; DOT: 2076; DOT label: Corrosive material, poison; molecular formula: C7H8O; FW: 108.14; RTECS: GO6475000; Merck Index: 12, 2645 Physical state, color, and odor: Colorless to pink crystals with a phenolic odor. Odor threshold concentration in water is 55 ppb (Buttery et al., 1988). An experimentally determined odor threshold concentration of 1 ppbv was reported by Leonardos et al. (1969) which exceeds the odor threshold concentration of 0.054 ppbv reported by Nagata and Takeuchi (1990). Melting point (°C): 34.8 (Weast, 1986) 36 (Huntress and Mulliken, 1941) Boiling point (°C): 202.3 (Gibbs, 1927) Density (g/cm3 at 20 °C): 1.0178 (Weast, 1986) 1.0341 (quoted, Standen, 1965) Diffusivity in water (x 10-5 cm2/sec): At ceff = 150 µM: 0.499 at 4.0 °C; 0.914 at 25.0 °C; 1.611 at 50.0 °C (Niesner and Heintz, 2000) Dissociation constant, pKa: 10.10 at 25 °C (Sprengling and Lewis, 1953) 10.20 (Hoigné and Bader, 1983) Flash point (°C): 87 (NIOSH, 1997) Lower explosive limit (%): 1.1 at 151 °C (NIOSH, 1997) Entropy of fusion (cal/mol⋅K): 9.195 (Poeti et al., 1982) 9.861 (Andon et al., 1967) Heat of fusion (kcal/mol): 2.8202 (Meva’a and Lichanot, 1990)

3.0370 (Andon et al., 1967) Henry’s law constant (x 10-7 atm⋅m3/mol): 2.20 at 8 °C (estimated, Leuenberger et al., 1985a) 7.69 at 25 °C (Parsons et al., 1972) 171.3 at 75.9 °C, 310.3 at 88.7 °C, 471.2 at 98.5 °C (VLE circulation still-UV spectro-photometry,

Dohnal and Fenclová, 1995) 34.3 at 25 °C (thermodynamic method-GC/UV spectrophotometry, Altschuh et al., 1999) 6.17 at 20.00 °C, 9.31 at 25.00 °C (dynamic equilibrium system-GC, Feigenbrugel et al., 2004a) Ionization potential (eV): 8.34 (Lias, 1998) Soil organic carbon/water partition coefficient, log Koc: 1.69 (Brookstone clay loam, Boyd, 1982) 3.53 (Apison and Fullerton soils), 2.06 (Dormont soil) (Southworth and Keller, 1986) 2.81 (Coyote Creek sediments, Smith et al., 1978) Kd = 0.9 mL/g on a Cs+-kaolinite (Haderlein and Schwarzenbach, 1993) Octanol/water partition coefficient, log Kow: 1.67 (Neely and Blau, 1985) 1.92 (quoted, Leo et al., 1971) 1.94 at 25 °C (Campbell and Luthy, 1985; shake flask-UV spectrophotometry, Fujita et al., 1964) 1.98 (RP-HPLC, Garst and Wilson, 1984) Solubility in organics: Miscible with ethanol, benzene, ethyl ether, glycerol (U.S. EPA, 1985), ethylene glycol, and toluene. Solubility in water: 13,000 mg/L at 8 °C (quoted, Leuenberger et al., 1985a) 24,000 and 53,000 mg/L at 40 and 100 °C, respectively (quoted, Verschueren, 1983) 0.022, 0.100, 54.00, and 164.0 g/L at 30, 105, and 138 °C, respectively (quoted, Standen, 1965) 22,000 mg/L at 25 °C (shake flask-HPLC/UV spectrophotometry, Varhaníčková et al., 1995a) 230 mM at 25 °C (Southworth and Keller, 1986) Vapor pressure (x 10-2 mmHg): 4 at 20 °C (quoted, Verschueren, 1983) 8 at 25 °C (quoted, Valsaraj, 1988) 10.8 at 25 °C (Smith et al., 1978) 13 at 25 °C (quoted, Howard, 1989) 2.0 at 8 °C, 12 at 25 °C (quoted, Leuenberger et al., 1985a) Environmental fate: Biological. Protocatechuic acid (3,4-dihydroxybenzoic acid) is the central metabolite in the bacterial degradation of 4-methylphenol. Intermediate by-products include 4-hydroxybenzyl alcohol, 4-hydroxybenzaldehyde, and 4-hydroxybenzoic acid. In addition, 4-methylphenol may undergo hydroxylation to form 4-methylcatechol (Chapman, 1972). Chloroperoxidase, a fungal enzyme isolated from Caldariomyces fumago, reacted with 4-methylphenol forming 4-methyl-2chlorophenol (Wannstedt et al., 1990). Under methanogenic conditions, inocula from a municipal

carbon dioxide and methane (Young and Rivera, 1985). A species of Pseudomonas, isolated from creosote-contaminated soil, degraded 4-methylphenol into 4-hydroxybenzaldehyde and 4-hydroxybenzoate. Both metabolites were then converted into protocatechuate (O’Reilly and Crawford, 1989). In the presence of suspended natural populations from unpolluted aquatic systems, the second-order microbial transformation rate constant determined in the laboratory was reported to be 2.7 ± 1.3 x 10-10 L/organism⋅h (Steen, 1991). Heukelekian and Rand (1955) reported a 5-d BOD value of 1.44 g/g which is 57.2% of the ThOD value of 2.52 g/g. In activated sludge inoculum, 96.0% COD removal was achieved. The average rate of biodegradation was 55.0 mg COD/g⋅h (Pitter, 1976). Photolytic. Photooxidation products reported include 2,2′-dihydroxy-4,4′-dimethylbiphenyl, 2hydroxy-3,4′-dimethylbiphenyl ether, and 4-methylcatechol (Smith et al., 1978). Anticipated products from the reaction of 4-methylphenol with ozone or OH radicals in the atmosphere are hydroxynitrotoluene and ring cleavage compounds (Cupitt, 1980). Absorbs UV light at a maximum wavelength of 278 nm (Dohnal and Fenclová, 1995). Reaction rate constants for the reaction of 4-methylphenol and NO3 in the atmosphere: 1.3 x 10-11 cm3/molecule⋅sec at 300 K (Japar and Niki, 1975), 1 x 10-11 cm3/molecule⋅sec at 300 K (Atkinson and Lloyd, 1984), 2.19 x 10-12 cm3/molecule⋅sec at 298 K (Atkinson et al., 1988), 1.07 x 10-11 cm3/molecule⋅sec at 296 K (Atkinson et al., 1992); with OH radicals in the atmosphere: 3.8 x 10-11 cm3/molecule⋅sec (half-life 10 h) at 300 K (Atkinson et al., 1979), 4.50 x 10-11 cm3/molecule⋅sec at 298 K (Atkinson and Lloyd, 1984; Atkinson, 1985); with ozone in the atmosphere: 4.71 x 10-19 cm3/molecule⋅sec at 296 K (Atkinson et al., 1982). Chemical/Physical. Kanno et al. (1982) studied the aqueous reaction of 4-methylphenol and other substituted aromatic hydrocarbons (toluidine, 1-naphthylamine, phenol, 2-and 3methylphenol, pyrocatechol, resorcinol, hydroquinone, and 1-naphthol) with hypochlorous acid in the presence of ammonium ion. They reported that the aromatic ring was not chlorinated as expected but was cleaved by chloramine forming cyanogen chloride. The amount of cyanogen chloride formed was increased as the pH was lowered (Kanno et al., 1982). In aqueous solution, 4-methylphenol was degraded by ozone at a reaction rate of 3.0 x 104/M⋅sec at pH range of 1.5 to 2 (Hoigné and Bader, 1983). Reported rate constants for the reaction of 4-methylphenol and singlet oxygen in water at 292 K: 1.1 x 107/M⋅sec at pH 8.3, 2.4 x 107/M⋅sec at pH 8.8, 1.6 x 108/M⋅sec at pH 10, 3.5 x 108/M⋅sec at pH 11.5 (Scully and Hoigné, 1987), and 9.6 x 106/M⋅sec for an aqueous phosphate buffer solution at 27 °C (Tratnyek and Hoigné, 1991). Exposure limits: NIOSH REL: TWA 2.3 ppm (10 mg/m3), IDLH 250 ppm; OSHA PEL: TWA 5 ppm (22 mg/m3); ACGIH TLV: TWA for all isomers 5 ppm (adopted). Symptoms of exposure: May cause weakness, confusion, depression of central nervous system, dyspnea, weak pulse, and respiratory failure. May irritate eyes and mucous membranes. Contact with skin may cause burns and dermatitis. Chronic effects may include gastrointestinal disorders, nervous disorders, tremor, confusion, skin eruptions, oliguria, jaundice, and liver damage (NIOSH, 1997; Patnaik, 1992). Toxicity: Acute oral LD50 for rats 207 mg/kg, mice 344 mg/kg (quoted, RTECS, 1985). LD50 (skin) for rats 750 mg/kg, rabbits 301 mg/kg (quoted, RTECS, 1985). Source: As 3+4-methylphenol, detected in distilled water-soluble fractions of 87 octane gasoline (6.03 mg/L), 94 octane gasoline (0.60 mg/L), Gasohol (1.76 mg/L), No. 2 fuel oil (1.84 mg/L), jet fuel A (0.43 mg/L), diesel fuel (1.318 mg/L), and military jet fuel JP-4 (0.92 mg/L) (Potter, 1996).