Volatile 1,1-dibromoethane

Volatilization is the most important removal process for 1,2-dibromoethane released to surface waters. Volatilization half-lives of 1-16 days have been estimated for flowing and standing surface waters. Sorption to sediment or suspended particulate material is not expected to be an important process (EPA 1987a, 1987b HSDB 1989). 

Biotic and abiotic degradation of 1,2-dibromoethane in surface waters is slow relative to volatilization of the compound to the atmosphere (ERA 1987b). 1,2- Dibromoethane is resistant to hydrolysis (Jaber et al. 1984) the hydrolytic half-life of the compound has been reported to range from 2.5 years (Vogel and Reinhard 1982) to 13.2 years (HSDB 1989). As a result of its hydrolytic stability and the limited biological activity in subsurface soils, 1,2- dibromoethane leached to groundwater is expected to persist for years. 

As a result of its persistence in soil and groundwater, and past widespread use as a gasoline additive and fumigant, 1,2-dibromoethane has been detected in ambient air, soils, groundwater, and food. However, most of the monitoring data reported in this section, although the latest available, are not current. Volatilization is the most important removal process for 1,2-dibromoethane released to surface waters. Since only a small fraction of the compound is sorbed to soil, sorption to sediment and subsequent persistence in sediment is not expected to be an important process in the removal of 1,2-dibromoethane from the environment. The data may reflect ambient concentrations of a decade or more ago, but because of the phaseout of the use of leaded gasoline and the ban on... 

High-resolution GC equipped with an appropriate detector is the most common analytical technique for determining the concentrations of 1,2-dibromoethane in air, water, wastewater, soil, leaded gasoline, and various foods (e.g., grains, grain-based foods, beverages, and fruits). The choice of a particular detector will depend on the nature of the sample matrix, the detection limit, and the cost of the analysis. Because volatile organic compounds in environmental samples may exist as complex mixtures or at very low concentrations, concentrations of these samples prior to quantification are... 

Gas purging and trapping is the most commonly used method for the preconcentration of 1,2-dibromoethane from water, waste water, soil, and various foods. This method also provides a preliminary separation of 1,2-dibromoethane from other less volatile and nonvolatile components in the samples, thereby alleviating the need for extensive separation of the components by a chromatographic column prior to quantification. 

The Environmental Health Laboratory Sciences Division of the National Center for Environmental Health and Injury Control, Centers for Disease Control, is developing methods for the analysis of 1,2-dibromoethane and other volatile organic compounds in blood. These methods use high resolution gas chromatography and magnetic sector mass spectrometry which gives detection limits in the low parts- per- trillion range. 

Sawhney BL, Pignatello JJ, Steinberg SM. 1988. Determination of 1,2-dibromoethane (EDB) in field soils Implications for volatile organic compounds. J Environ Qual 17 149-152. 

The lead oxide is not volatile and would accumulate in the engine if dibromoethane and dichloroethane were not added. These substances react with Pb02 and form a volatile compound, PbBr2 or PbCh, which is eliminated in the exhaust. 

In addition to the tetraethyl or tetramethyl lead, both types of antiknock fluids also contained 1,2-dichloroethane and 1,2-dibromoethane (ca. 35% by weight) to react with the lead released on combustion to form lead bromide and lead chloride. These lead halides are volatile at the cylinder combustion temperatures of 800-900°C, and leave the combustion chamber with the exhaust, which prevented the buildup of lead deposits. This was also the final step in the chain of events occurring with the alkylated lead antiknock compounds, which contributed to the widespread dispersal of lead compounds to the air and soil wherever gasoline powered vehicles operated. For this reason, and the toxic exposures during refueling, the alkylated lead addition rate was reduced to not more than 0.5 g of contained lead per U.S. gallon by 1980, even for leaded gasolines [29], and was phased out in the U.S. and Canada by 1985. 

A solution of lithium bis(trimethylsilyl)bismuthide-2 THF (25.3 g, 50 mmol) in pentane (100 ml) was added slowly to a cooled (-30°C) solution of 1,2-dibromoethane (4.7 g, 25 mmol) in the same solvent (100 ml). As the reaction proceeded, lithium bromide precipitated from a yellowish orange reaction mixture. Liberated ethylene gas (24.6 mmol) was collected into an inverted stand cylinder above water. After completion of the reaction, the precipitate was filtered off and washed successively with pentane. The volatiles were distilled off in vacuo at 20°C to leave a solid residue, which was recrystallized from pentane. The yield was 13.5 g (76%) [82ZN(B)91],... 

Before extraction, soil and sediment samples may be dried, for example, by freeze-drying — provided that volatile compounds are not to be analyzed — or by mixing with anhydrous sodium sulfate and extraction in a Soxhlet apparatus. It should, however, be noted that it has frequently been found advantageous to add low concentrations of water, and this is consistent with the finding that addition of water to dry soils inhibits sorption of PAHs (Karimi-Lotfabad et al. 1996). If wet samples are to be analyzed directly, acetonitrile, propan-2-ol, or ethanol may be employed first, and these may be valuable in promoting the chemical accessibility of substances sorbed onto components of the matrices the analyte may then be extracted into water-immiscible solvents and the water phase discarded. Alternatively, if the analyte is sufficiently soluble in, for example, benzene, the water may be removed azeotropically in a Dean Stark apparatus and the analyte then extracted with the dry solvent. Analytes may, however, be entrapped in micropores in the soil matrix so that, for example, recovery of even the volatile 1,2-dibromoethane required extraction with methanol at 75°C for 24 h (Sawhney et al. 1988). 

Ethylene dibromide (EDB or dibromoethane) is a volatile liquid produced by the bromination of ethylene. EDB is used as a lead scavenger in leaded gasoline and as a pesticide and fumigant in soil and on grain, fruits, and vegetables. Because EDB has been classified as a suspected human carcinogen and is a male reproductive toxin, its use as a pesticide has been restricted since 1984. 

Herzfeld D, Van Der Gun K-D, Louw R. 1989. Quantitative determination of volatile organochlorine compounds in water by GC-headspace analysis with dibromoethane as an internal standard. Chemosphere 18 1425-1430. 

Dibromo-3-chloropropane (DBCP) ( Nemagon ) and 1,2-dibromoethane are volatile nematocide formerly used to rid soil of these undesirable worms. Plants are remarkably tolerant to them but they are toxic to humans. 

Solvent use is controlled by both state and federal regulations. The federal Clean Air Act Amendments of 1990 mandate controls on solvent use in the industry. Almost all organic solvents are classified as Volatile Organic Compounds (VOCs) under Title I of the 1990 Amendments and these regulations will require further reductions in future solvent use. Title III of the 1990 Amendments contains a long list of substances considered Hazardous Air Pollutants (HAPs). Many of the halogenated solvents are on the HAP list. The solvents discussed in this chapter and that are on the HAP list include methylene chloride, chloroform, carbon tetrachloride, 1,1,1-trichloroethane, trichloroethylene, 1,2-dichloroethane, 1,2-dibromoethane, bromoform, and chlorobenzene. The Maximum Achievable Control Technology (MACT) stan-... 

Deposits of lead oxide in the exhaust tube and combustion engine shortened the durability of the motor components when leaded gasoline was used. From 1928, therefore, dichloroethane and dibromoethane were added as scavengers to the antilmock fluid, so that the lead oxide formed during combustion was converted to the more volatile lead halogenides (Nickerson 1954). 

It is of interest that A//° (gas phase) for dibromoethane is greater than that for butane (3.7-4.1 kJ mol ) even though bromine and methyl are usually considered to be of comparable size. This suggests that a factor other than steric repulsion affects the situation the obvious candidate is dipole-dipole repulsion in the gauche conformers of the dibromide. This contributor to the overall repulsion should be diminished in more polar solvents, both because of an increase in the effective dielectric constant and a concomitant decrease in coulom-bic repulsion, and because of more effective solvation of the higher-dipole confotmer in more polar solvents. Indeed, A// for 1,2-dibromoethane diminishes to 3.6 kJ mol in the pure liquid (dielectric constant e = 4.8) and to 2.8 kJ mol in acetonitrile (e = 37.5). (It must be noted, however, that because of differential volatility of the gauche and anti conformers of (nonpolar) butane, the conformational enthalpy difference A//° between these conformers also diminishes in the liquid phase, to 2.3-2.4 kJ mol .) We indicated earlier that ethane has a threefold potential (called V3). In the 1,2-dihaloethane, there is a superposed onefold potential (Vi) since the optimum (anti) orientation of the C-X dipoles is achieved only once in the course of a 360° rotation about the C-C bond. 

Gas chromatography is generally suitable for determining nonionics of low molecular weight in environmental matrices, provided that volatile derivatives are formed as discussed in Chapter 8. HBr cleavage coupled with GC determination of the dibromoethane... 

Condensation reactions yielding cyclic and/or linear oligosulfides were studied by four research groups [89-93]. In 1863, Husemann [89] prepared an intermediate by condensation of 1,2-dibromoethane with sodium sulfide. By heating he obtained the cyclic dimer, dithiane, as a volatile degradation product. Mansfeld [90] reinvestigated this reaction and interpreted the intermediate as polymer, but he speculatively assigned the formula of a cyclic trimer. Husemann also prepared poly(methylene sulphide) from dibromomethane and sodium sulfide. Furthermore, he performed condensations of dibromomethane and dibromoethane, respectively, with sodium trithiocarbonate, which was easily obtained from sodium sulfide and carbon disulfide. He isolated a five-membered cyclic ethylene trithiocarbonate, but a polymeric methylene trithiocarbonate the molar mass of which remained obscure. 

---