Bromotrichloromethane

Description

Bromotrichloromethane (BrCCl3) is practically insoluble in water, but it is soluble in all proportions in alcohol and ether, and miscible with many organic liquids. Uncatalyzed addition of bromotrichloromethane to ethylene can lead to violent explosion. It is frequently used in organic synthesis and as a flame retardant. The general population may be exposed to bromotrichloromethane via ingestion of food and drinking water. Bromotrichloromethane has been identified as a volatile compound in both bacon and pork. Production of bromotrichloromethane has been banned in the United States, and therefore occupational exposure would only occur when using BrCCl3 for organic synthesis. The acute lethal dose in humans is 500–5000 mg kg^-1. Inhalation of 20 000 ppm for 60 min will result in surgical anesthesia and possibly death. Based on effects in monkeys and rats, this compound may induce coma and possibly death in humans exposed to 20 000 ppm for 60 min; 10 000 ppm for 30 min will provoke marked incoordination; 2000 ppm for 5 min may produce disturbance of equilibrium. BrCCl3 exposure to cells can cause destruction of CYP450 (drug-metabolizing enzymes), making cells resistant to toxicity. This compound is considered a prolific inducer of lipid peroxidation as measured by MDA (malondialdehyde production) and 4-HNE (4-hydroxynonenal concentration).

Chemical properties

Clear colourless to slightly yellow liquid

The Uses of Bromotrichloromethane

Although bromotrichloromethane is no longer produced in the United States, it is still used in organic syntheses of various compounds.

The Uses of Bromotrichloromethane

Organic synthesis.

The Uses of Bromotrichloromethane

Used in the bromination of benzylic positions under sunlamp irradiation. Employed as chain transfer agent for radical polymerization of methacrylates. It can also be employed as brominating reagent of active hydrogen compounds.

What are the applications of Application

Bromotrichloromethane is a versatile reagent used in the bromination of active hydrogen compounds

Hazard

Toxic by ingestion and inhalation of fumes.

Safety Profile

Poison by ingestion and intraperitoneal routes. Narcotic in high concentration. Mutation data reported. See also CHLOROFORM. Incompatible with ethylene. When heated to decomposition it emits very toxic fumes of Cland Br-.

Environmental Fate

With the loss of bromide ion, mediated by cytochrome P450 enzyme in the liver, the trichlorocarbon free radical is responsible for lipid peroxidation, which is the predominant mechanism of hepatotoxicity. BrCCl3, when metabolized in vitro and in vivo, produces phosgene (COCl2) and trichloromethyl free radicals that ultimately cause massive lipid peroxidation and depletion of cellular glutathione. Both these events contribute to toxicity. Activation of membrane phospholipase A2 has also been considered as another prime suspect contributing to toxic outcomes. It is also known to cause cerebellar degeneration in rodents. It is cytotoxic to the sperm in the testes at the time of exposure. Renal tumors are induced in male mice due to depletion of glutathione, increased lipid peroxidation, and DNA lesions.

Purification Methods

Wash it with aqueous NaOH solution or dilute Na2CO3, then with H2O, and dry with CaCl2, BaO, MgSO4 or P2O5 before distilling in diffuse light and storing in the dark. It has also been purified by treatment with charcoal and fractional crystallisation by partial freezing. It is purified also by vigorous stirring with portions of conc H2SO4 until the acid did not discolour during several hours stirring. Wash with Na2CO3 and water, dry with CaCl2 and then illuminate it with a 1000W projection lamp at 15cm for 10hours, after making it 0.01M in bromine. Pass it through a 30 x 1.5cm column of activated alumina and fractionally redistil it through a 12-in Vigreux column (p 11). [Firestone & Willard J Am Chem Soc 83 3511 1961; see also Cadogan & Duell J Chem Soc 4154 1962, Beilstein 1 IV 77.]

Toxicity evaluation

Bromotrichloromethane is no longer produced in the United States. However, its use during organic syntheses may result in its release to the environment. If released to the atmosphere, bromotrichloromethane is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase bromotrichloromethane slowly degrades in the atmosphere by reaction with photochemically produced hydroxyl radicals; the half-life for this reaction in air is estimated to be greater than 44 years. Photolysis occurs based on bromotrichloromethane’s structural similarity to other halogenated methane compounds but not at an environmentally important rate. In soil, bromotrichloromethane is expected to have low mobility based on an estimated Koc of 567. The potential for volatilization of bromotrichloromethane from dry soil surfaces may exist based on this compound’s vapor pressure. Bromotrichloromethane may volatilize from moist soil surfaces based on an estimated Henry’s Law constant of 3.7×10^-4 atm-cu m mol^-1 at 25°C. Volatilization from water surfaces is expected based on the estimated Henry’s Law constant for this compound. Estimated volatilization half-lives from a model river and model lake are 7.4 h and 6.6 days, respectively. An estimated bioconcentration factor of 49 suggests the potential for bioconcentration in aquatic organisms is moderate. Biodegradation of bromotrichloromethane in the environment is expected to be slow because of its highly halogenated structure. Occupational exposure to bromotrichloromethane may occur through inhalation or dermal contact with this compound in workplaces where it is produced or used. The general population may be exposed to bromotrichloromethane via ingestion of food and drinking water.