Oxidation of hydrogen iodide

As to catalytic reactions in homogeneous media, Moritz Traube found in his studies of the oxidation of hydrogen iodide by hydrogen peroxide in aqueous solution, that the catalyst ferrous sulfate is activated by copper sulfate (5). As to the magnitude of such effects, Price stated in 1898 (6) that the simultaneous action of iron and of copper compounds on the reaction between persulfate and hydrogen iodide causes an unexpected acceleration of the reaction, which is more than twice as great as the acceleration calculated as an additive effect of the two single catalysts. However, effects were also observed of the opposite kind,... 

Other solutions to dealing with interferences in the detection of H O have included the use of a copperfll) diethyldithiocarbamate precolumn to oxidize the sample before it reaches the immobilized enzyme, as well as the use of a palladium/gold sputtered electrode which catalyzes the oxidation of hydrogen peroxide In addition, peroxidase has been used to catalyze the reaction between hydrogen peroxide and iodide ferrocyanide and organo-fluorine compounds Am-... 

The Iodometric method has also been utilized in analyzing hydrogen sulfide in the air (EPA 1978). The method is based on the oxidation of hydrogen sulfide by absorption of the gas sample in an impinger containing a standardized solution of iodine and potassium iodide. This solution will also oxidize sulfur dioxide. The Iodometric method is suitable for occupational settings. The accuracy of the method is approximately 0.50 ppm hydrogen sulfide for a 30-L air sample (EPA 1978). 

According to the authors cited above, equation (16) holds for the decomposition of hydrogen iodide on platinum and of nitrous oxide on gold, and furthermore, according to Schwab and Drikos (12), for the oxidation of carbon monoxide to carbon dioxide on copper oxide. 

Methyl iodide is likely generated from methyl acetate and HI (equation 7) a portion of the iodide species in the reaction mixture certainly exists in the form of hydrogen iodide (equations 11, 12). Iodide ion tends to attack the -carbon of the alkyl portion of unhindered esters ( 7). Thus, methyl acetate, which would be in general inert to the metal complexes used, is converted to a reactive species which can readily oxidatively add to a palladium(0) complex. An... 

The ineffectiveness of hydrogen iodide as a catalyst promoter can now be rationalized, since HI reacts with Ru3(CO)12 or Ru(CO)s to produce Ru(CO)4I2 or [Ru(CO)3I3] , Ru(II) halide complexes which are stable under H2/CO and inactive as catalysts (191). These oxidized halide complexes can... 

Rice, Fryling, and Weselowski (J. Amer. Chem. Soc., 1924, 46, 2405) make all reaction rates proportional to the concentration of what they call residual molecules, which have to be formed endothermically from one of the reactants. The proportion of these increases with temperature and accounts for the increase in reaction rate. Something of this kind may be true in special cases, for example, in the formation of HBr the residual molecule would be the bromine atom. But this resolution into atoms is only the limiting case of ordinary activation, and it is difficult indeed to see what the residual molecule could be, or what tautomeric change could occur in the simple decomposition of hydrogen iodide or nitrous oxide. 

Many examples of this type of reaction are known the decomposition of arsine the decomposition of phosphine on surfaces of glass, f porcelain, J silica the decomposition of formic acid vapour on a variety of different surfaces— glass, platinum, rhodium, titanium oxide, and others the decomposition of nitrous oxide on the surface of gold Tf the decomposition of sulphuryl chloride on the surface of glass the decomposition of hydrogen iodide on the surface of platinum ff the decomposition of hydrogen selenide on the surface of selenium. J J A general discussion... 

It is probable that the actual mechanism of the decomposition is unimolecular, but, the observed order of the reaction being zero, we cannot tell whether the molecules decompose singly or by interaction with their neighbours. The catalytic decomposition of hydrogen iodide on the surface of platinum can actually be shown to be unimolecular. The heat of activation in this instance is even lower (14,000 cals.), but is again subject to the same uncertainty as the values for the unimolecular reactions of nitrous oxide. 

Holmes209 reported briefly on the results of a study of the reaction between nitric oxide and hydrogen iodide over the temperature range 363-573°K. This obviously complex reaction was represented by the overall reaction... 

The reaction was studied at nitric oxide and hydrogen iodide pressures of 40-500 and 120-750 torr, respectively. The reaction rate was determined by analyzing for NO and I2 at various times and, in some cases, for ammonium iodide and hydrogen iodide. In clean Pyrex vessels results were not reproducible, but in vessels seasoned with a carbonaceous deposit reproducibility was satisfactory and the reaction was observed to be homogeneous. The rate law was determined to be second order... 

Later, Holmes and Sundaram210 studied the gas phase photolysis of hydrogen iodide in the presence of nitric oxide. NO was found to inhibit the reaction by reducing the quantum yields of hydrogen and iodine to an equal extent. The mechanism proposed was... 

Perhaps the earliest recorded illustration of the use of hydrogen iodide ia the reaction of tetraphenylethylene oxide (Eq. 404), which yields 1,1,2,2-tetraphenylethane in the presence of phosphorus.171 ... 

Bassam Z. Shakhashiri, "Hydrogen Peroxide Iodine Clock Oxidation of Potassium Iodide by Hydrogen Peroxide," Chemical Demonstrations, A Handbook for Teachers of Chemistry, Vol. 4 (The University of Wisconsin Press, Madison, 1992), pp. 37-43. 

The generation of (difluoroiodo)arenes by anodic oxidations of aryl iodides in the presence of excess Et3N nHF is a notable recent development (Scheme 31) [96,97]. Because the fluoroiodanes are activated by hydrogen-bonding with HF, such reagent combinations are especially useful for electrophilic fluorinations of organic compounds. When oxidation potentials of the aryl iodides are lower than those of the substrates, indirect anodic fluorinations of the latter can be achieved. 

Methyldiiodoarsine [m.p. 30° b.p. 128° (16 mm.)] forms odorless yellow needles which melt to a red liquid and volatilize without decomposition at 200°. The compound is somewhat soluble in water and moderately soluble in alcohol, ether, and carbon disulfide the solubility is increased by the presence of hydrogen iodide. Hydrogen chloride or bromide converts the diiodoarsine into the corresponding chloro or bromo compound, while iodine oxidizes the compound to methylarsenic oxide.8 When boiled with dry sodium carbonate in the presence of benzene, methyldiiodoarsine forms the corresponding oxide.5... 

Phosphoric acid is a much weaker oxidizing agent than sulphuric acid, and it fails to oxidize either hydrogen bromide or hydrogen iodide. The brown color, it is true, indicates a trace of free iodine, but this is accounted for by a direct decomposition of hydrogen iodide by heat. 

A similar photolytic cyclization has been achieved, with concomitant oxidation, of the iV-formyl-enamine (85) in the presence of hydrogen iodide to produce (86), no evidence being found of non-oxidative cyclization. The enamine with the (Z)-configuration is obtained directly from the 3,4-dihydroisoquinoline by the action of formic acid and acetic anhydride.95... 

Iron and iodine interact in the presence of water, evolving heat, ferrous iodide passing into solution. The reaction appears to take place in stages involving the formation of ferric iodide, which decomposes into ferric oxide and hydrogen iodide, the last-named attacking the free iron with the formation of ferrous iodide.2... 

Oxidative addition of methyl iodide to the coordinalively unsaturated cobalt (I) species (1) gives the methyl complex (2) which undergoes CO insertion, probably via methyl migration. Elimination of iodine from the acetyl complex (3) and oxidative addition of hydrogen gives (5). Reductive elimination of the primary product acetaldehyde leads to the unsaturaied complex (6) which oxidatively adds iodine. The catalytic cycle is closed by the elimination of hydrogen iodide from (7), which is consumed by reaction with methanol to give methyl iodide. 

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