ABSTRACT
H3C Note: According to Chevron Phillips Company’s (2004) Technical Data Sheet, 99.0-99.5 wt % 2,2-dimethylbutane contains 2,3-dimethylbutane (0.2 wt %), cyclopropane (0.2 wt %), and 2methylpentane (0.1 wt %). CASRN: 75-83-2; DOT: 2457; molecular formula: C6H14; FW: 86.18; RTECS: EJ9300000 Physical state, color, and odor: Clear, colorless liquid with a mild petroleum-like odor. Liquid quickly evaporates and forms conbustible fumes. An odor threshold concentration of 20 ppmv was reported by Nagata and Takeuchi (1990). Melting point (°C): -99.9 (Weast, 1986) Boiling point (°C): 49.7 (Weast, 1986) Density (g/cm3): 0.6485 at 20 °C (Weast, 1986) 0.6570 at 25 °C (Hawley, 1981) Diffusivity in water (x 10-5 cm2/sec): 0.75 at 20 °C using method of Hayduk and Laudie (1974) Dissociation constant, pKa: >14 (Schwarzenbach et al., 1993) Flash point (°C): -47.8 (Sax and Lewis, 1987) -34 (Aldrich, 1990) Lower explosive limit (%): 1.2 (Sax and Lewis, 1987) Upper explosive limit (%): 7.0 (Sax and Lewis, 1987) Heat of fusion (kcal/mol): 0.138 (Dean, 1987) Henry’s law constant (atm⋅m3/mol): 1.69 at 25 °C (Mackay and Shiu, 1981) Interfacial tension with water (dyn/cm): 49.7 at 25 °C (quoted, Freitas et al., 1997)
10.06 (HNU, 1986) 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: 3.82 (Hansch and Leo, 1979) Solubility in organics: In methanol: 590 and 800 g/L at 5 and 10 °C, respectively. Miscible at higher temperatures (Kiser et al., 1961). Miscible with other aliphatic hydrocarbons, e.g., pentane, hexane, heptane, etc. Solubility in water (mg/kg): 21.2 at 25 °C (shake flask-GLC, Price, 1976) 18.4 at 25 °C (shake flask-GC, McAuliffe, 1963, 1966) 39.4 at 0 °C, 23.8 at 25 °C (shake flask-GC, Polak and Lu, 1973) Vapor density: 3.52 g/L at 25 °C, 2.98 (air = 1) Vapor pressure (mmHg): 325 at 24.47 °C (Willingham et al., 1945) 319.1 at 25 °C (Wilhoit and Zwolinski, 1971) Environmental fate: Photolytic. Reported photooxidation rate constants for the reaction of 2,2-dimethylbutane with OH radicals at 297, 299, and 300 K are 2.59 x 10-12, 6.16 x 10-12, and 2.59 x 10-12 cm3/molecule⋅sec, respectively (Atkinson, 1985, 1990). Chemical/Physical. Complete combustion in air yields carbon dioxide and water vapor. 2,2Dimethylbutane will not hydrolyze because it has no hydrolyzable functional group. Exposure limits: ACGIH TLV: TWA and STEL for all isomers except n-hexane are 500 and 1,000 ppm, respectively (adopted). Source: Comprised 0.1 vol % of total evaporated hydrocarbons from gasoline tank (quoted, Verschueren, 1983). Schauer et al. (1999) reported 2,2-dimethylbutane in a diesel-powered medium-duty truck exhaust at an emission rate of 310 µg/km. California Phase II reformulated gasoline contained 2,2-dimethylbutane at a concentration of 5,720 mg/kg. Gas-phase tailpipe emission rates from gasoline-powered automobiles with and without catalytic converters were 800 and 195,000 µg/km, respectively (Schauer et al., 2002). Reported as an impurity (0.2 wt %) in 99.0-99.7 wt % 2,3-dimethylbutane (Chevron Phillips, 2004). Use: Intermediate for agricultural chemicals; in high octane fuels.
