Hydrogen peroxide reaction with iodide ions

Any species dissolved in the water is clearly going to be subject to chemical reaction with these ultrasonically produced radicals and/or hydrogen peroxide. Thus if iodide ion is present in solution iodine will be liberated. Spin trapping ESR techniques afforded positive identification of the radical species sonically generated in water [40]. 

If, in the reaction mixture described, twice the volume of 10% sodium hydroxide solution and 25 ml. of 30% hydrogen peroxide are employed and the reaction mixture is refluxed until it no longer gives a positive peroxide test with iodide ion (about 30 minutes to 1 hour), the product is diphenic acid (m.p. 220-223°) in 73-85% yield. 

Probably the most famous clock reaction is an iodine clock reaction, a redox reaction involving hydrogen peroxide and acidified iodide ions. The iodine is not seen when the reactants are first mixed because it is being converted to colourless iodide ions in a reaction with another reactant. The reaction of the acidified iodide ions with hydrogen peroxide is ... 

In kinetic investigations of this reaction, sodium thiosulfate (substance P) of known concentration together with a little starch solution (substance Q) are added to the mixture of hydrogen peroxide and acidified iodide ions. The iodine produced by the main reaction immediately reacts with thiosulfate ions ... 

Other examples are the use of osmium(VIII) oxide (osmium tetroxide) as catalyst in the titration of solutions of arsenic(III) oxide with cerium(IV) sulphate solution, and the use of molybdate(VI) ions to catalyse the formation of iodine by the reaction of iodide ions with hydrogen peroxide. Certain reactions of various organic compounds are catalysed by several naturally occurring proteins known as enzymes. 

The quantity of hydrogen peroxide found was not equivalent to the acid sorption. Catalytic decomposition might be responsible for this. The formation of peroxide-like substances when moist air and acid reacted on carbon was deducted by Lamb and Elder (114), Kolthoff (20), and King (33) from the positive potassium iodide-starch test and, in my laboratory, from the reaction with titanyl ions. 

The reaction between hydrogen peroxide and iodide ions Hydrogen peroxide can react as an oxidant or a reductant. In the titrimetric determination of hydrogen peroxide, it usually reacts as a reductant when a strong oxidant is used as a titrant. In the reaction with iodide, hydrogen peroxide reacts as an oxidant. The iodine produced in this reaction can be reduced by thiosulphate back to iodide. In presence of thiosulphate, the reaction is similar to the reaction in Sec.7.6.1. It was found that molybdates act as catalysts. This fact is the basis of a titrimetric method for determination of the latter ions. 

Disulfides can be prepared by treatment of alkyl halides with disulfide ions and also indirectly by the reaction of Bunte salts (see 10-41) with acid solutions of iodide, thiocyanate ion, or thiourea, or by pyrolysis or treatment with hydrogen peroxide. Alkyl halides also give disulfides when refluxed with sulfur and NaOH, and with piperidinium tetrathiotungstate or piperidinium tetrathiomolybdate. ... 

Guideline 13. If the order of a reaction with respect to one or more species increases as the concentration of that species increases, it is an indication that the reaction may be proceeding by two or more parallel paths. Liebhafsky and Mohammed (6) have reported that for the reaction between hydrogen peroxide and iodide ion, the order with respect to hydrogen ion increases from zero to one as the pH is decreased. 

Iodide ion-selective electrode The iodide electrode has broad application both in the direct determination of iodide ions present in various media as well as for the determination of iodide in various compounds. It is, for example, important in the determination of iodide in milk [44,64,218, 382, 442], This electrode responds to Hg ions [150, 306, 439] and can be used for the indirect determination of oxidizing agents that react with iodide, such as 10 [305], lOi [158], Pd(II) [117, 347,405] and for the determination of the overall oxidant content, for example in the atmosphere [393], It can also be used to monitor the iodide concentration formed during the reactions of iodide with hydrogen peroxide or perborate, catalyzed by molybdenum, tungsten or vanadium ions, permitting determination of traces of these metals [12,192,193, 194, 195]. The permeability of bilayer lipid membranes for iodide can be measured using an I"... 

Although unstable with respect to water and oxygen, hydrogen peroxide decomposes only very slowly at room temperature because the reaction has a high activation energy (76 kj/mol). In the presence of iodide ion, however, the reaction is appreciably faster (Figure 12.16) because it can proceed by a different, lower-energy pathway ... 

Amongst other inorganic catalysts are to be included the iodides 9 (also bromides and chlorides but less active) and chromates or dichromates. The agent in the former case appears to be the iodide ion, the mechanism of the reaction probably involving oxidation to hypo-iodite which then reacts with more hydrogen peroxide with formation... 

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