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