ABSTRACT
Br CASRN: 96-12-8; DOT: 2872; molecular formula: C3H5Br2Cl; FW: 236.36; RTECS: TX8750000; Merck Index: 12, 3068 Physical state, color, and odor: Colorless when pure, however, technical grades are yellowish to dark brown. Pungent odor at high concentrations Melting point (°C): 5 (NIOSH, 1997) Boiling point (°C): 196 (Windholz et al., 1983) Density (g/cm3): 2.093 at 14 °C (Windholz et al., 1983) 2.05 at 20 °C (Hawley, 1981) Diffusivity in water (x 10-5 cm2/sec): 0.81 at 20 °C using method of Hayduk and Laudie (1974) Flash point (°C): 76.7 (open cup, NIOSH, 1997) Henry’s law constant (x 10-4 atm⋅m3/mol): 2.49 at 20 °C (approximate - calculated from water solubility and vapor pressure) Soil organic carbon/water partition coefficient, log Koc: 2.11 (Kenaga and Goring, 1980) 1.49-2.16 (Panoche clay loam, Biggar et al., 1984) 2.48, 2.55 (Fresno, CA aquifer solids, Deeley et al., 1991) Octanol/water partition coefficient, log Kow: 2.63 using method of Hansch et al. (1968). 2.49 and 2.51 were estimated using fragment contribution methods of Boto et al. (1984) and
Viswanadhan et al. (1989), respectively. Solubility in organics: Miscible with oils, dichloropropane, and isopropanol (Windholz et al., 1983) Solubility in water: 1,270 ppm (Kenaga and Goring, 1980)
9.66 g/L at 25 °C, 8.16 (air = 1) Vapor pressure (mmHg): 0.8 at 21 °C (quoted, Verschueren, 1983) Environmental fate: Biological. Soil water cultures converted 1,2-dibromo-3-chloropropane to 1-propanol, bromide, and chloride ions. Precursors to the alcohol formation include allyl chloride and allyl alcohol (Castro and Belser, 1968). Soil. Biodegradation is not expected to be significant in removing 1,2-dibromo-3-chloropropane. In aerobic soil columns, no degradation was observed after 25 d (Wilson et al., 1981). The reported half-life in soil is 6 months (Jury et al., 1987). Groundwater. According to the U.S. EPA (1986), 1,2-dibromo-3-chloropropane has a high potential to leach to groundwater. Deeley et al. (1991) calculated a half-life of 6.1 yr for 1,2-dibromo-3-chloropropane in a Fresno, CA aquifer (pH 7.8 and 21.1 °C). Chemical/Physical. 1,2-Dibromo-3-chloropropane is subject to both neutral and base-mediated hydrolysis (Kollig, 1993). Under neutral conditions, the chlorine or bromine atoms may be displaced by hydroxyl ions. If nucleophilic attack occurs at the carbon-chlorine bond, 2,3dibromopropanol is formed which may undergo reaction to give 2,3-dihydroxybromopropane via the intermediate epibromohydrin. 2,3-Dihydroxybromopropane undergoes hydrolysis via the intermediate 1-hydroxy-2,3-propylene oxide which reacts with water forming glycerol. If the nucleophilic attack occurs at the carbon-bromine bond, 2-bromo-3-chloropropanol is formed which reacts forming the end product glycerol (Kollig, 1993). If hydrolysis of 1,2-dibromo-2chloropropane occurs under basic conditions, the compound will undergo dehydrohalogenation forming 2-bromo-3-chloropropene and 2,3-dibromo-1-propene as intermediates. Both compounds are subject to attack forming 2-bromo-3-hydroxypropene as the end product (Burlinson et al., 1982; Kollig, 1993). The hydrolysis half-life at pH 7 and 25 °C was calculated to be 38 yr (Burlinson et al., 1982; Ellington et al., 1986). The rate constants for the reaction of 1,2-dibromo-3-chloropropane with ozone and OH radicals in the atmosphere at 296 K are <5.4 x 10-20 and 4.4 x 10-13 cm3/molecule⋅sec (Tuazon et al., 1986). The smaller rate constant for the reaction with ozone indicates that the reaction with ozone is not an important atmospheric loss of 1,2-dibromo-3-chloropropane. The calculated photolytic half-life and tropospheric lifetime for the reaction with OH radicals in the atmosphere are 36 and 55 d, respectively. The compound 1-bromo-3-chloropropan-2-one was tentatively identified as a product of the reaction of 1,2-dibromo-3-chloropropane with OH radicals. In water, 1,2-dibromo-3-chloropropane (0.045 mM) reacted with OH radicals (pH 2.7). Reaction rates were 3.2 x 108/M⋅sec and 4.2 x 108/M⋅sec (Haag and Yao, 1992). At influent concentrations of 1.0, 0.1, 0.01, and 0.001 mg/L, the GAC adsorption capacities were 4.8, 2.2, 1.0, and 0.46 mg/g, respectively (Dobbs and Cohen, 1980). Emits toxic chloride and bromide fumes when heated to decomposition (Lewis, 1990). Exposure limits: Potential occupational carcinogen. No standards have been established. NIOSH (1997) recommends the most reliable and protective respirators be used, i.e., a self-contained breathing apparatus that has a full facepiece and is operated under positive-pressure or a suppliedair respirator that has a full facepiece and is operated under pressure-demand or under positivepressure in combination with a self-contained breathing apparatus operated under pressuredemand or positive-pressure. OSHA, however, recommends a PEL TWA of 1 ppb. Symptoms of exposure: Ruth (1986) reported an irritation concentration of 1.93 mg/m3 in air.
