Bromo-methane

Several lower partially halogenated hydrocarbons (dichloromethane, bromo-methane, trichloroethylene, 1,1,1-trichloroethane) have no measurable flash point, but are nonetheless capable of forming flammable and explosive mixtures with air, and several such accidents are recorded. 

Svirbely, J.L., Highman, B., Alford, W.C. von Oettingen, W.F. (1947) The toxicity and narcotic action of mono-chloro-mono-bromo-methane with special reference to inorganic and volatile bromide in blood, urine and brain. J. ind. Hyg. Toxicol., 29, 382-389... 

Preparation of the title compound by interaction of dimethyl sulfoxide and bromo-methane, sealed into a resin-coated glass bottle and heated at 65°C, led to an explosion after 120 h. The isolated salt thermally decomposes above 180°C to produce formaldehyde and a residue of methanesulfonic acid. In solution in dimethyl sulfoxide, the salt begins to decompose after several hours at 74—80°C (after exposure to light), the exothermic reaction accelerating with vigorous evolution of vapour (including formaldehyde and dimethyl sulfide), the residue of methanesulfonic acid finally attaining 132°C. Some white solid, probably poly-formaldehyde, is also produced. The explosion... 

SYNS BROMOCHLOROMETHANE HALON 1011 D METHYLENE CHLOROBROAnDE MIDB-4394-B MONO-CHLORO-MONO-BROMO-METHANE... 

METHYL ETHYL BROMO-METHANE (78-76-2) Forms explosive mixture with air (flash point 70°F/21°C). Reacts violently with strong oxidizers. 

Beilstein Handbook Reference) AI3-15514 BRN 1730801 Bromochloromethane CCRIS 817 Chlorobromomethane Chloromethyl bromide EINECS 200-826-3 Fluorocarbon 1011 Halon 1011 HSDB 2520 Methane, bromochloro- Methylene chlorobromide MII-B4394-B Mono-chloro-mono-bromo-methane NSC 7294 UN1887. Has been used In refrigeration and fire retardents. Has been identified as an ozone-threatening chemicals and subjected to restrictions. Liquid mp = -87.9° bp = 68.0° d = 1,9344 poorly soluble in H2O, soluble in organic solvents. 

Alkyl halides can be very toxic to biological organisms. For example, bromomethane is used to kill termites and other pests. Bromo-methane works by methylating the NH2 and SH groups of enzymes, thereby destroying the enzymes ability to catalyze necessary biological reactions. Unfortunately, bromomethane has been found to deplete the ozone layer (Section 13.12), so its production has recently been banned in developed countries developing countries will have until 2015 to phase out its use. 

Figure 11.6 Steric hindrance to the 5 2 reaction. As the modeis indicate, the carbon atom in (a) bromo-methane is readiiy accessibie, resuiting in a fast 5 2 reaction. The carbon atoms in (b) bromoethane (primary), (c) 2-bromopropane (secondary), and (d) 2-bromo-2-methyipropane (tertiary) are successiveiy more hindered, resulting in successively slower Sn2 reactions.

Gillotay, D., Simon, P.C. Ultraviolet absorption spectrum of trifluoro-bromo-methane, difluoro-dibromo-methane and difluoro-bromo-chloro-methane in the vapor phase. J. Atmos. Chem. 8, 41-62 (1989)... 

Halomethanes have numerous industrial applications (Table 3.2). One of the most important of the group, chloroform, is used mainly as a solvent and an intermediate in the production of various products. Chloromethane and tribromomethane are also employed as chemical intermediates, whereas dichloromethrae is widely used as a solvent. Tribromomethane is a common fumigant, and fluoro-derivatives find general application as refrigerants and aerosol propellants. Recent restrictions placed on the use of fluorocarbons have resulted in a decrease in US production of fluoro-derivatives. During the last decade, production of trichlorofluoromethane declined from 1.3 to 0.7 X 10 tons while dichlorofluoromethane fell from 2.0 to 1.5 X 10 tons (Table 3.1). Production of other halomethanes has shown a consistent albeit small increase in recent years (Table 3.1). Total dichloromethane production now exceeds 2.5 X 10 tons compared with 1.5 and 1.8X itf tons for chloromethane and chloroform, respectively. It is estimated that bromo-methane production will be only about 2.0 X 10 tons in 1982. 

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