- γ-HIO3 - A metastable, centrosymmetric polymorph of iodic acid
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From solutions of chromium(III) perchlorate and periodic acid, single crystals of γ-HIO3 were obtained and characterized by single-crystal X-ray diffraction, Raman spectroscopy and thermal analysis. The compound crystallizes in the orthorhombic crystal system, space group Pbca (a = 563.92, b = 611.10, c = 1507.16 pm). The structure is built up by dimers (HIO3)2, which are formed by hydrogen bonds. The crystals are metastable and transform into the stable modification, α-HIO 3, within a couple of weeks.
- Fischer, Andreas,Lindsjoe, Martin
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- Kinetics of iodous acid disproportionation
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The iodous acid disproportionation is autocatalytic, and it is not easy to measure the rate constant of the step 2IO2H → IO 3- + IOH + H+ separately. Hg(II) was used previously to suppress the autocatalytic pathway, but this method presents difficulties discussed in this work. A more effective method is the use of crotonic acid, an effective IOH scavenger. It suppresses side reactions, and a purely second-order rate law is obtained. The rate constant decreases from 5 to 0.2 M-1 s-1 when the sulfuric acid concentration increases from 0.08 to 0.60 M. The observed decrease could be explained if IO 2- reacts faster than IO2H. This may have consequences for the mechanism of the oscillating Bray-Liebhafsky reaction.
- Schmitz, Guy,Furrow, Stanley D.
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supporting information
p. 525 - 530
(2013/07/26)
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- Iodine(I) reagents in hydrochloric acid-catalyzed oxidative iodination of aromatic compounds by hydrogen peroxide and iodine
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Hydrochloric acid activates the oxidative iodination of aromatic compounds with the iodine- hydrogen peroxide system through the formation of an iodine(I) compound as the iodinating reagent. Activation with hydrochloric acid is more powerful than that with sulfuric acid. The formation of dichloroiodic(I) acid (HICl2) with various forms of hydrogen peroxide was followed using UV spectroscopy. The HICl2 was used as the iodinating reagent. In the preparative oxidative iodinaton of various aromatic compounds, hydrochloric acid was used in a catalytic amount and the iodine(I) reagent was formed in situ with 0.5 equiv. hydrogen peroxide and 0.5 equiv. molecular iodine. Two types of reactivity were observed in oxidative iodination with iodine(I) species catalyzed by hydrochloric acid: in the iodination of anisole 1a better yields of iodination were observed with a smaller amount of hydrochloric acid, while on the contrary 4-tert-butyltoluene 1b gave better yields of iodination upon increasing the amount of hydrochloric acid. Reactivity was further manipulated by the choice of the solvent (MeCN, trifluoroethanol, hexafluoro-2-propanol). Copyright
- Bedrac, Leon,Iskra, Jernej
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p. 1243 - 1248
(2013/06/27)
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- Conductometric and Spectrophotometric Studies on the Ionization of Iodine and Its Compounds in Chlorosulphuric Acid
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Iodine and a few of its compounds form low valent polyatomic cations of iodine in chlorosulphuric acid medium.Conductometric redox titrations of iodine with the solutions of oxidizing agents like K2S2O8 in HSO3Cl indicate the formation of the cations I2(+) and I(+), which however, disproportionate to I3(+) and I(SO2Cl)3.Potassium iodide, iodine monochloride, iodic acid and iodine pentoxide produce reddish-brown coloured solutions characteristic of I3(+) cation.Iodine trichloride, however ionizes to yield ICl2(+).Conductometric titration of iodine against iodine trichloride in the acidic medium indicates the formation of I2Cl(+).
- Siddiqi, Z. A.,Ansari, N. A.,Aslam, M.,Lutfullah,Zaidi, S. A. A.
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