ABSTRACT
CASRN: 591-76-4; molecular formula: C7H16; FW: 100.20 Physical state, color, and odor: Clear, colorless, flammable, watery liquid with an odor similar to pentane, 2-methylpentane, 3methylpentane, hexane, and 3-hexane. An odor threshold concentration of 420 ppbv was reported by Nagata and Takeuchi (1990). Melting point (°C): -118.3 (Weast, 1986) Boiling point (°C): 90 (Weast, 1986) Density (g/cm3): 0.67859 at 20 °C, 0.67439 at 25 °C (Dreisbach, 1959) Diffusivity in water (x 10-5 cm2/sec): 0.70 at 20 °C using method of Hayduk and Laudie (1974) Dissociation constant, pKa: >14 (Schwarzenbach et al., 1993) Flash point (°C): <-17.7 (Hawley, 1981) Heat of fusion (kcal/mol): 2.195 (quoted, Riddick et al., 1986) Henry’s law constant (atm⋅m3/mol): 0.512 at 26.9 °C, 0.311 at 35.0 °C, 0.256 at 45.0 °C (dynamic headspace, Hansen et al., 1995) Soil organic carbon/water partition coefficient, log Koc: Unavailable because experimental methods for estimation of this parameter for aliphatic hydrocarbons are lacking in the documented literature Octanol/water partition coefficient, log Kow: 3.30 (Coates et al., 1985) Solubility in organics: Soluble in acetone, alcohol, benzene, chloroform, ligroin, and ether (Weast, 1986). Miscible with liquid aliphatic hydrocarbons. Solubility in water: 3.8 mg/L at 23 °C (Coates et al., 1985) 2.54 mg/kg at 25 °C (shake flask-GLC, Price, 1976)
4.10 g/L at 25 °C, 3.46 (air = 1) Vapor pressure (mmHg): 65.9 at 25 °C (Wilhoit and Zwolinski, 1971) Environmental fate: Biological. Riser-Roberts (1992) reported 2-and 5-methylhexanoic acids as metabolites by the microorganism Pseudomonas aeruginosa. Photolytic. Based on a reported photooxidation reaction rate constant of 6.80 x 10-12 cm3/molecule⋅sec with OH radicals, the half-life of 2-methylhexane is 25 h (Altshuller, 1990). Chemical/Physical. Complete combustion in air produces carbon dioxide and water vapor. 2Methylhexane will not hydrolyze because it does not contain a hydrolyzable functional group. Source: Schauer et al. (1999) reported 2-methylhexane in a diesel-powered medium-duty truck exhaust at an emission rate of 570 µg/km. Schauer et al. (2001) measured organic compound emission rates for volatile organic compounds, gas-phase semi-volatile organic compounds, and particle-phase organic compounds from the residential (fireplace) combustion of pine, oak, and eucalyptus. The gas-phase emission rate of 2-methylhexane was 2.6 mg/kg of pine burned. Emission rates of 2-methylhexane were not measured during the combustion of oak and eucalyptus. California Phase II reformulated gasoline contained 2-methylhexane at a concentration of 15.3 g/kg. Gas-phase tailpipe emission rates from gasoline-powered automobiles with and without catalytic converters were 2.88 and 372 mg/km, respectively (Schauer et al., 2002). Use: Organic synthesis. Component of gasoline.
