Chlorine dioxide oxidation equivalents

Reaction between arsenic(tll) and chlorate is fairly slow. Although the reaction can be markedly accelerated by osmium tetroxide as catalyst , the quantitative reduction of chlorates takes nearly an hour. In the case of the induced reaction it was assumed that arsenic(III) is oxidized to arsenic(IV) by 1-equivalent oxidizing agents. Chlorate is reduced to chlorine dioxide by the arsenic(IV) intermediate, viz. 

In this reaction five oxidation equivalents are released. For example, 1 M Cl02 solution contains 5 x 35.5 = 177.5 g/liter of active chlorine. In alkaline media, chlorine dioxide is reduced to chlorite involving a change of only one oxidation equivalent. 

In another procedure, oxidation is carried out in the presence of chloride ions and ruthenium dioxide [31]. Chlorine is generated at the anode and this oxidises ruthenium to the tetroxide level. The reaction medium is aqueous sodium chloride with an inert solvent for the alkanol. Ruthenium tetroxide dissolves in the organic layer and effects oxidation of the alkanol. An undivided cell is used so that the chlorine generated at the anode reacts with hydroxide generated at the cathode to form hypochlorite. Thus this electrochemical process is equivalent to the oxidation of alkanols by ruthenium dioxide and a stoichiometric amount of sodium hypochlorite. Secondary alcohols are oxidised to ketones in excellent yields. 1,4- and 1,5-Diols with at least one primary alcohol function, are oxidised to lactones while... 

The iodometric method depends on the fact that chromates interact with hydrochloric acid, liberating chlorine, which in its turn liberates an equivalent amount of iodine from potassium iodide. The iodine may then be determined by titration with standard sodium thiosulphate. This method is largely used for chromium in whatever state of oxidation it may be, a chromium salt being first converted to chromate either by fusion v th sodium peroxide or by boiling its solution wdth nitric acid and lead dioxide. - ... 

Bridgcd Sulfonamides The methods available for the preparation of the sulfonamide bridge at the 3 and 4 position of the pyrazole are somewhat limited by the type of reactions that can be supported at these positions. In contrast to this, numerous methods are available for the introduction of the sulfonamide at the 5 position. They include (a) Meerwein Reaction/amination (b) oxidative chlorination/amination and (c) metalation followed by trapping of the resultant anion with sulfur dioxide or an equivalent. 

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