1 -Bromo-3-chloromethane

The atmospheric chemistry of other bromo-chloromethanes that are present in smaller amounts in the troposphere (Fig. 12.44) is discussed by Orkin et al. (1997) and Bilde et al. (1998). 

Thiazetidines may be prepared by alkylation of the sodium salts obtained conveniently by thiocarbamoylation of the sulfonamides 191 with isothiocyanates in the presence of sodium hydride in DMF. Alkylation with bromo-chloromethane or dibromomethane yields the substituted 2-imino-l,3-thiazetidines 41 <2002SUL105>. 

T. Class, K. Ballschmiter, Chemistry of organic traces in air. VIII Sources of bromo- and bromo-chloromethanes in marine air and surface water of the Atlantic Ocean, J. Atmos. Chem., 6 (1988), 35 6. 

Similar addition reactions were observed with the bridged [l.l.l]propellane system tetra-cyclo[5.1.0.0 .0 ]octane (16) when reacted with diethyl ether, carbon tetrachloride, bromo-chloromethane, iodomethane, tert-butyl bromide, benzyl bromide and tri(butyl)tin hydride. ... 

Fluorination of vinorelbine was thus performed in super acid medium (HF-SbFs). A super electrophilic agent, such as a chloromethyl or a Br+ cation is generated in s/fu from a chloromethane (CHCI3, CCI4) or from N-Bromo Succinimide (NBS). It is able to abstract a hydrogen from the protonated alkaloid, leading to a cation that can be trapped by an halide anion present in the medium [105,106], Difluorination remarkably occurs selectively at C-4 of the clavamine fragment (Fig. 37) [105]. 

Whereas simple haloalkanes play a very important role in synthetic and mechanistic organic chemistry in the ground state, the interest in excited-state reactions centres more on polyhaloalkanes and on vinyl or aryl halides. Chloromethane absorbs only in the far ultraviolet (X-, . 173 nml, but ionger-wavelength absorption occurs for bromo- or iodo-cornpounds (CH, has A, 258 nrn and for polyhalo-compounds (iodoform, CHIj, has A, 349 nm and is coloured yellowi. 

The halonium structure 17 was also attributed107 to protonated bromo- and chloromethane, in agreement with theoretical predictions105,106. However, in these two ions an additional interaction (stronger for the bromo than for the chloro compound) is present between the hydrogen bonded to the halogen and the carbon atom107. Protonated iodomethane, on the contrary, structurally resembles protonated methane with the proton bonded to the carbon atom. These conclusions are supported by both MI and CID data for protonated and deuterated halomethanes and by thermochemical data. 

Fig. 2. Relative scale of the Tc of the main HTSC groups and solidification points of different mixed solvents chloroethane + butyronitrile (I), n-pentane + methylcyclohexane + n-propanol (II), bromo-ethane + butyronitrile + isopentane + methylcyclopentane (III), chloromethane + dimethyl ether (IV), bromoethane + butyronitrile (V), propionitrile + butyronitrile (VI), methanol + dichloromethane (VII), ammonia + isopropanol + dimethylformamide (VIII). Data are taken from [28, 152].

With medium-sized cyclic compounds, transannular reactions have been observed. The reaction of cyclooctene with carbon tetrachloride and bromotri-chloromethane is an interesting example. As shown in the equation below, bromo-trichloromethane adds in a completely normal manner, but carbon tetrachloride gives some 4-chloro-l-trichloromethylcyclooctane as well as the expected product ... 

In 1976, Farrall and Frechet described the bromination of 1% crosslinked polystyrene resins with bromine in the presence of catalytic amounts of thallium triacetate (TTA) or thallium(iii) chloride under reflux in tetra-chloromethane in the dark, which led to the bromo-polystyrene products with highly reproducible degree of functionalisation, typically from 0.39 to 0.45. According to the authors, the degree of functionalisation was independent of the catalyst loading and was a function of the amount of bromine used. The polymers thus obtained were colourless as well as cleaner compared to those obtained by bromination catalysed by classical iron(iii) chloride. 

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. 

Chloroform, bromo-form, dichlorobromo-methane, dibromo-chloromethane Non volatile organic chlorine compounds... 

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