Bromoform bromotrichloromethane

The reaction can be carried out efficiently using aryl diazonium tetrafluoroborates with crown ethers, polyethers, or phase transfer catalysts.103 In solvents that can act as halogen atom donors, the radicals react to give aryl halides. Bromotrichloromethane gives aryl bromides, whereas methyl iodide and diiodomethane give iodides.104 The diazonium ions can also be generated by in situ methods. Under these conditions bromoform and bromotrichloromethane have been used as bromine donors and carbon tetrachloride is the best chlorine donor.105 This method was used successfully for a challenging chlorodeamination in the vancomycin system. 

Allenylcobaloximes, e.g. 26, react with bromotrichloromethane, carbon tetrachloride, trichloroacetonitrile, methyl trichloroacetate and bromoform to afford functionalized terminal alkynes in synthetically useful yields (Scheme 11.10). The nature of the products formed in this transformation points to a y-specific attack of polyhaloethyl radicals to the allenyl group, with either a concerted or a stepwise formation of coba-loxime(II) 27 and the substituted alkyne [62, 63]. Cobalt(II) radical 27 abstracts a bromine atom (from BrCCl3) or a chlorine atom (e.g. from C13CCN), which leads to a regeneration of the chain-carrying radical. It is worth mentioning that the reverse reaction, i.e. the addition of alkyl radicals to stannylmethyl-substituted alkynes, has been applied in the synthesis of, e.g., allenyl-substituted thymidine derivatives [64],... 

Pecher et al. (2002) show how the uptake of ferrous iron from aqueous solution, by iron oxides, leads to the formation of a variety of reactive surface species that are capable of reducing polyhalogenated methanes (PHMs). The iron oxides used in the experiments and their characteristics are shown in Table 16.2. The PHMs studied include bromodichloromethane (CHBrCl ), chlorodibromomethane (CHBr Cl), bromoform (CHBr ), tetrachloromethane (CCl ), hexachloroethane (HCE), fluorotribromomethane (CFBrj), bromotrichloromethane (CBrCl ) and dibromodichloromethane (CBr Cy. 

FIGURE 7.11 Time-resolved single-beam CARS transients (left column) and corresponding Fourier spectra (right column) for bromotrichloromethane (CBrClj), chloroform (CHClj), bromoform (CHBrj) and a mixture of the three constituents. This result shows that the different components can clearly be distinguished by their characteristic vibrational resonances, (von Vacano and Motzkus 2007b). (From von Vacano and Motzkus, Phys. Chem. Chem. Phys., 10 681-691, 2008. Used with permission.)... 

Photolysis of this polymer gives radicals on which side chains can be formed, giving graft polymerization 122, 123, 153). Similarly the polymerization of styrene (152) or vinyl acetate (157) in the presence of bromotrichloromethane gives telomers carrying terminal bromine atoms and trichloromethyl groups. By ultraviolet irradiation (3500 A) in the presence of methyl methacrylate the carbon-bromine links are broken and block copolymers are formed. The telomerization of acrylonitrile and acrylic acid with bromoform is based on the same technique the end groups of both polyacrylonitrile and polyacrylic acid were photolyzed in the presence of acrylamide and afforded polyacrylamide blocks linked to polyacrylonitrile or polyacrylic acid blocks (164, 165). 

Redistribution of halogens in chloroform and bromoform is taking place in presence of aluminum trichloride226 and also in presence of sodium hydroxide under PTC227. Bromotrichloromethane isomerizes to a mixture of all the possible five isomers in presence of traces of chloroform and Bu4NF (TBAF) catalyst (equation 28)228 ... 

Benzocyclopropene reacts with a variety of radical reagents (for example A -bromosuccinimide carbon tetrachloride bromotrichloromethane bromoform/benzoyl peroxide alkyl sulfide and ethane-1,2-dithiol with photolysis) to afford products derived from cleavage of the cyclopropane ring. The preferential mode of reaction consists of a chain reaction initiated by radical addition at Cl a followed by opening of the cyclopropyl radical to afford a benzyl radical. Yields are generally low except for the addition of the alkylsulfanyl radical, e.g. formation of 1, and no products derived from addition to the central tt-bond are formed. Cyclopropa[A]naphthalene reacts similarly with radicals and gives 2-methylnapthalene derivatives, while no addition to the central 7i-bond is observed. ... 

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