Bromine electrolytic” method

The electrolytic method is an indirect oxidation, as the small amount of bromide present is constantly converted to bromine, the actual oxidant. Essentially the reaction is the same as the action of bromine in weakly acidic buffered solution. The presence of only a small amount of extraneous salts is of advantage in processing the reaction mixture. The... 

A variation of the bromine oxidation process which seems to be particularly feasible for the commercial production of aldonic acids involves the electrolysis between carbon electrodes of solutions containing sugars, small amounts of bromides, and a buffer such as calcium carbonate 179), Presumably the reaction takes place by the formation of free bromine at the anode the bromine oxidizes the aldose to the aldonic acid and is reduced to bromide. Yields are almost theoretical in many cases. If the electrolytic method is not well controlled, saccharic acids and 2-keto and 5-keto aldonic acids may be produced 180), Whereas the normal electrolytic oxidation is conducted with direct current, a yield of 55 % of gluconic acid has been obtained with alternating current 181) and platinum electrodes a very low efficiency was observed with graphite electrodes. 

Greater utilization of periodate as an oxidant has been suggested in the development of an electrolytic method (228) starch is oxidized in 2 % sulfuric acid containing iodic acid. This method is similar in concept to the electrolytic bromine method of Isbell and Frush 179),... 

An electrolytic method has been developed for the a-bromination of active methylene compounds such as a-substituted malonates and acetoacetates. Yields range from 73 to 84%. 

Anodic hydroxylation/methoxylation of furans has an exact chemical counterpart in the well-known bromine/methanol reaction, and the choice of method is not always easily made. One can compare the two methods particularly easily in syntheses of the flavoring component, the pyrone maltol 121, from the furan 122 since one group used the electrolytic method299 and another the chemical method.300... 

Chlorine is the most abundant of the halogens, especially in sea water, a ton of which contains in grams chlorine 15,000, bromine 97, iodine 0-17 (ratio 106 6,000 1). Its preparation depends on the discharge of its ion, either directly (i.e., electrolytically) or by oxidation. The older methods of oxidation (by manganese dioxide or by air in presence of certain catalysts) have now been replaced for technical purposes by the electrolysis of sodium chloride, which is primarily for the production of caustic soda, the chlorine being a by-product the chloroparaffins which are now so much used as solvents were developed to utilize this chlorine. 

A number of other methods exist for the a halogenation of carboxylic acids or their derivatives. Under electrolytic conditions with NaCl, malonates are converted to 2-chloro malonates.Acyl halides can be a brominated or chlorinated by use of A-bromo- or A-chlorosuccinimide and HBr or HCl. The latter is an ionic, not a free-radical halogenation (see 14-3). Direct iodination of carboxylic acids has been achieved with l2-Cu(II) acetate in HOAc. Acyl chlorides can... 

Alternatively, a single-stage electrochemical route can be used, in which a non-aqueous electrolyte containing an alkylammonium salt and dissolved halogen, for example bromine or iodine, is employed. This method has the advantage of yielding a crystalline product which requires no further purification or recrystallization. 

Utilizing concentrated electrolyte solutions is an intuitive method to increase ionic conductivity and amount of active material present in the system. This approach certainly raises operating efficiencies and improves the kinetic parameters of electrode activity, as expected [6]. There is a concurrent drawback, however, that increasing the amount of electrochemically active species present in the electrolyte might negatively influence diffusion parameters due to the resultant increase in kinematic viscosities of the solution [37, 38]. As is the case of the zinc half-cell, the kinetics and behavior of the Br2/Br redox reaction in the bromine half-cell are also influenced by the presence and concentrations of supporting electrolytes in solution [39]. 

Addition methods were used for the determination of m-saturated compounds and olefins. The methods are based on the additions of bromine to unsaturated bonds, and the waves for the brominated compounds corresponding to the reduction of o, j8-dibromides (involving elimination) are measured. Their heights are proportional to the concentration of the unsaturated compound. Thus vinylchloride and 1,2-dichloroethylene were transformed into l-chloro-l,2-dibromoethane and l,2-dichloro-l,2-dibromoethane, by the action of a 3 M solution of bromine in methanol saturated with sodium bromide. The excess of bromine was removed with ammonia and the polarographic analysis was performed with sodium sulphite or lithium chloride as a supporting electrolyte. On the other hand, acetylene, vinyl-chloride, 1,2-dichloroethylene and 1,1,2-trichloroethylene were determined ) after a 24 hr reaction with bromine in glacial acetic acid (1 1). The excess bromine was removed with a stream of nitrogen or carbon dioxide. An aliquot portion is diluted (1 10) with a 3 M solution of sodium acetate in 80 per cent acetic acid and after deaeration the curve is recorded. 

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