BROMOCHLOROMETHANE

Br Cl CASRN: 74-97-5; DOT: 1887; molecular formula: CH2BrCl; FW: 129.39; RTECS: PA5250000 Physical state, color, and odor: Clear, colorless liquid with a sweet, chloroform-like odor Melting point (°C): -87.5 (quoted, Riddick et al., 1986) Boiling point (°C): 68.1 (Weast, 1986) Density (g/cm3): 1.9344 at 20 °C (Weast, 1986) 1.9229 at 25 °C (Dreisbach, 1959) Diffusivity in water (x 10-5 cm2/sec): 1.13 at 20 °C using method of Hayduk and Laudie (1974) Flash point (°C): Not applicable (NIOSH, 1997) Lower explosive limit (%): Not applicable (NIOSH, 1997) Upper explosive limit (%): Not applicable (NIOSH, 1997) Henry’s law constant (x 10-3 atm⋅m3/mol): 1.44 at 25 °C (approximate - calculated from water solubility and vapor pressure) Ionization potential (eV): 10.77 ± 0.01 (Franklin et al., 1969) Soil organic carbon/water partition coefficient, log Koc: 1.43 using method of Chiou et al. (1979) Octanol/water partition coefficient, log Kow: 1.41 at 25 °C (generator column-HPLC/GC, Tewari et al., 1982; Wasik et al., 1981) Solubility in organics: Soluble in acetone, alcohol, benzene, ether (Weast, 1986), and many other solvents, particularly chlorinated hydrocarbons. Solubility in water: 129 mM at 25.0 °C (generator column-HPLC, Tewari et al., 1982; generator column-HPLC/GC,

15 g/kg H2O at 25 °C (O’Connell, 1963) Vapor density: 5.29 g/L at 25 °C, 4.47 (air = 1) Vapor pressure (mmHg): 115 at 20 °C (NIOSH, 1997) 141.07 at 24.05 °C (Kudchadker et al., 1979) 93.3 at 15.72 °C, 141.1 at 24.06 °C, 335.5 at 44.71 °C (dynamic boiling point method, McDonald

et al., 1959) Environmental fate: Biological. When bromochloromethane (5 and 10 mg/L) was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum for 7 d, 100% biodegradation with rapid adaptation was observed (Tabak et al., 1981). Photolytic. The following rate constants were reported for the reaction of bromochloromethane and OH radicals as measured by both flash photolysis resonance fluorescence and discharge flow electron paramagnetic resonance techniques (x 10-13 cm3/molecule⋅sec): 0.91 at 4 °C, 1.11-1.13 at 25 °C, 1.32-1.34 at 40 °C, 1.55-1.58 at 57 °C, 1.76-1.90 at 76 °C, 2.10-2.26 at 97 °C (Orkin et al., 1997). Chemical/Physical. Although no products were identified, the estimated hydrolysis half-life in water at 25 °C and pH 7 is 44 yr (Mabey and Mill, 1978). Bromochloromethane reacts with bisulfide ion (HS-), produced by microbial reduction of sulfate, forming 1,3,5-trithiane and dithiomethane. Estimated reaction rate constants at 25 and 35 °C were 7.29 x 10-5 and 2.42 x 104/M⋅sec, respectively (Roberts et al., 1992). Exposure limits: NIOSH REL: TWA 200 ppm (1,050 mg/m3), IDLH 2,000 ppm; OSHA PEL: TWA 200 ppm; ACGIH TLV: TWA 200 ppm (adopted) Toxicity: LC50 (inhalation) for mice 15,850 mg/m3/8-h, rats 28,800 ppm/15-min (quoted, RTECS, 1985). Acute oral LD50 for rats 5,000 mg/kg, mice 4,300 mg/kg (quoted, RTECS, 1985). Drinking water standard: No MCLGs or MCLs have been proposed, however, a DWEL of 0.5 mg/L was recommended (U.S. EPA, 2000). Source: Naturally formed by algal biological processes (Orkin et al., 1997) and is a disinfection byproduct in public water treatment systems. Uses: Fire extinguishing agent; cleaning agent in industrial applications; organic synthesis.