Bromination, using clays

Water has been shown to be an effective solvent in some chemical reactions such as free radical bromination. Supercritical fluids such as liquified carbon dioxide are already commonly used in coffee decaffeination and hops extraction. However, supercritical carbon dioxide can also be used as a replacement for organic solvents in polymerization reactions and surfactant production. Future work may involve solventless or neat reactions such as molten-state reactions, dry grind reactions, plasma-supported reactions, or solid materials-based reactions that use clay or zeolites as carriers. 

In kaolin (clay) processing, sulfur dioxide reduces colored impurities, eg, iron compounds. In the bromine industry, sulfur dioxide is used as an antioxidant in spent brine to be reinjected underground. In agriculture, especially in California, sulfur dioxide is used to increase water penetration and the avadabiHty of soil nutrients by virtue of its abiHty to acidulate saline—alkaH soils (327). It is also usefiil for cleaning ferric and manganese oxide deposits from tile drains (328). 

Wunsche An electrolytic process for liberating bromine from a bromide solution. It uses carbon electrodes and a porous clay separator. Developed in Germany in 1902. See also Kossuth. 

Bhattacharjee369, who has brominated acetanilide suspended in aqueous solution of potassium bromide and hydrogen peroxide in presence of vanadium pent oxide catalyst. Chloroperoxidase has been mimicked using supported manganese phorphyrin catalyst in the oxychlorination of dimedone370 and by clay-supported iron(III) chloride in the oxy-chlorination of toluene and anisole371. The kinetics and mechanism of the haloper-oxidases have been studied extensively372,373. 

Salmon et al. used a natural montmorillonite to catalyse the intermolecular condensation of toluene in the presence of bromine to produce ortho- and para-phenyltolylmethanes.31 The reaction was carried out at reflux using carbon disulfide as a solvent. The first stage of the reaction is believed to be the generation of benzyl bromide. A bromide ion is abstracted from benzyl bromide by a Lewis acid site on the clay surface. The resulting electrophilic benzyl cation then attacks toluene. 

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