Iodate Ions Research Articles

Benzylmalonic acid reaction with iodine and behavior in a Briggs–Rauscher oscillator

AbstractBenzylmalonic acid (BzMA) reacts via an enol mechanism with aqueous iodine to form rather stable iodobenzylmalonic acid. In the presence of iodate, which oxidizes iodide to di‐iodine, the reaction goes to completion. The kinetics of the reaction BzMA + I2 + IO3− + H+ have been studied and the results were interpreted with a suitable mechanism. In a mixture with acidic iodate, hydrogen peroxide, and manganous ions, BzMA can serve as a substrate for a Briggs–Rauscher‐type oscillating reaction. The behavior of this oscillator has been studied in detail. A mechanistic interpretation of the oscillations based on a new kinetic model is also given. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 357–365, 2002

Modification of the electroosmotic flow and separation selectivity of anions in electrochromatography with pseudo-stationary phases of C14-alkyldimethylammoniopropane sulfonate zwitterionic surfactants by addition of salts to the background electrolyte.

The effects of salts (NaCl, NaClO4, MgCl2, CeCl3) added to background electrolyte (BGE) solutions (10 mmol L(-1) sodium phosphate, pH 7.2) on electroosmotic flow (EOF) and the separation selectivity of anions (chloride, bromide, iodide, nitrite, nitrate, chlorate, thiocyanate, iodate, chromate, and molybdate ion) by capillary electrochromatography using the zwitterionic surfactant 3-(N,N-dimethylmyristylammonio)propane sulfonate (C14N3S) as a pseudo-stationary phase were investigated. There are two mechanisms affecting the separations: 1. the cations and anions of the added salts interact with the zwitterionic surfactant to varying degrees, thus changing the overall retention of the analytes; and 2. they change the EOF and the resulting apparent mobilities. It was shown that a BGE containing perchlorate and a low concentration of zwitterionic surfactant (2 mmol L(-1)) gave a stable and reproducible EOF and the concentration of perchlorate could be used to manipulate the separation selectivity for polarizable anions, such as iodide and thiocyanate. These effects are discussed in terms of measured association constants describing the interaction of anions and cations with the zwitterion.

Kinetic Determination of Iodide Based on its Effect on the Hydrogen Peroxide Oxidation of Triflupromazine

A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H2O2. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of H2O2. The optimum reaction conditions are TFP (0.4 × 10−3 M), H2SO4 (1.0M), H3PO4 (2.0M), and H2O2 (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm−3 and a detection limit of 0.04 ng ċ cm−3, based on the 3 Sb criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as 0.2, 1.0, 2.0, and 4.0 ng ċ cm−3 of I−, IO3 -, or IO4 - in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide determination.

Single‐crystal Raman studies on nickel iodate dihydrate, Ni(IO3)2·2H2O

AbstractSingle‐crystal Raman spectra in the range 4000–35 cm−1 and the results of group theoretical treatment including Cartesian symmetry coordinates of nickel iodate dihydrate, Ni(IO3)2 · 2H2O, (space group Pbca, Z = 4) are presented and discussed with respect to the strength of the HO—HOIO3 hydrogen bonds and the extent of intramolecular (intraionic) coupling of the stretching vibrations of both the hydrate H2O molecules and the iodate IO3− ions. The energies and relative intensities of the IO stretching modes in the various species of the unit‐cell group D2h reveal that the iodate ions of the title compound behave as if they possess pseudo C2v site symmetry with a at least partly uncoupled IO stretch due to the significantly shortest (175.5 pm) IO arm and a symmetric (νs) and an antisymmetric stretching vibration (νas) due to the remaining IO2 group (rI–O = 184.2 and 186.0 pm). The respective site‐group modes decrease in the order ν3a ↔ νIO(1) (mean value of the respective unit‐cell group modes: 804 cm−1) > ν1 ↔ νs (772 cm−1) > ν3b ↔ νas (744 cm−1) (ν1 and ν3 as for distorted C3v IO3− ions). For the IO3− bending modes (430–300 cm−1) and the lattice modes below 300 cm−1 the true vibrational modes are not known. The normally used assignment to a symmetric (ν2) and an asymmetric bending vibration (ν4) as for C3v IO3− ions is at least questionable. The hydrogen‐bond distances calculated from the wavenumbers of the OD stretching modes of matrix‐isolated HDO molecules do not fully agree with the data of a neutron diffraction study performed in 1972. Copyright © 2001 John Wiley & Sons, Ltd.

Absorption of iodine from aqueous solutions on nuclear reactors alloys

Iodide ions I-, molecular iodine I2 and iodate ions IO3 - absorption has been studied on the three alloys which are present, in majority, in french nuclear reactors: Inconel 600, Zircaloy and 304L stainless steel. Iodide and iodate anions are not absorbed on the three considered alloys and contribute only for a negligible quantity to iodine retention on the nuclear reactors materials. Molecular iodine is absorbed according to: 304 stainless steel < Zircaloy < Inconel 600. Influence of pH has been studied: absorption increases in acidic medium and decreases in basic medium. Molecular iodine absorption increases with temperature.Phenomenons which occur with iodine during the cold shutdown of a nuclear reactor and during its restart are discussed from the point of vue of iodine volatilization risk.

Spectrophotometric determination of periodate and iodate by a differential kinetic method

A rapid, simple and sensitive differential kinetic method is presented for the determinations of periodate and iodate ions. The method is based on their reaction with iodide in the presence of methylene blue. The reactions can be monitored spectrophotometrically by measuring the decrease in absorbance at 665 nm. Two sets of conditions were established that in one set of conditions only periodate reacted with iodide but in the other set both the ions reacted with iodide during the first 180 s after initiation of the reaction. The data were evaluated by proportional equations. The method allowed the determination of periodate and iodate at concentrations between 0.1 and 1.0 and 0.1 and 1.3 μg ml −1, respectively. The method was applied to the determination of periodate and iodate in tap water and spring water with satisfactory results.

The Illustration of Multistability

Multistability, a phenomenon that can appear in certain nonlinear systems, is usually described by discussing the possible steady-state solutions of some nonlinear process as given by an abstract mathematical model having a single variable and one or more control or bifurcation parameters. In the present paper, the model of a real reaction is offered: the illustration of multistability is carried out on a model for the hydrogen peroxide decomposition into water and oxygen in the presence of iodate and hydrogen ions, the Bray-Liebhafsky oscillatory reaction.

Determination of cyclodextrin content using periodate oxidation by capillary electrophoresis

A simple and general method suitable for the determination of cyclodextrin content in various matrices is described. The proposed method involves selective cleavage of C–C bonds with vicinal hydroxyl groups by means of periodate (Malaprade’s reaction). The amount of produced iodate is monitored by capillary electrophoresis. Optimized electrophoretic conditions (20 m M disodium tetraborate with 1 m M tetradecyltrimethylammonium bromide, direct UV detection λ=200 nm) ensure complete separation of periodate and iodate ions and sufficient sensitivity towards iodate. Under optimized reaction conditions (2-fold excess of periodate, temperature 70°C) reproducible quantitative results were obtained for α-, β- and γ-cyclodextrins as model samples. The proposed method was tested on a real sample of acrylamide — 2 I- O-allyl-β-CD copolymer. The values of β-cyclodextrin content were compared with those obtained by reference NMR measurement and were found to be identical.

Secondary ion emission from keV energy atomic and polyatomic projectile impacts on sodium iodate

Sodium iodate and sodium iodide are inorganic solids in which iodine exists in different chemical environments. In sodium iodate, the iodine atom is bonded to oxygen to make the trigonal pyramidal IO 3 anion, which in turn is incorporated with sodium into an ionic crystal. In sodium iodide, however, the iodide anion and sodium cation are ionically bound in a crystal lattice. Nearly half of the negative secondary ion yield generated from keV energy polyatomic ion impacts on a sodium iodate surface is characteristic of ion emission expected from sodium iodide (i.e. (NaI) n I −), yet x-ray photoelectron spectroscopy data indicate that the solid material resulting from aliquots of aqueous sodium iodate dried on stainless steel contains no more than 2% sodium iodide. To determine how the number of atoms in the primary ion influences the amount of iodide type ion formation from sodium iodate, secondary ion yield measurements were performed using Cs, (CsI)Cs, and (CsI) 2Cs projectiles incident at energies ranging from 10 to 25 keV. The experiments were run on an event-by-event basis at the level of single ion impacts. The yields of iodate (composed of Na, I, and O) and iodide type secondary ions increase with the energy of the projectile and the number of constituent atoms. When compared on a per-incident atom basis, however, we found that the yields of secondary ions characteristic of iodate saturate at three total projectile atoms, but continue to increase nonlinearly for iodide species (i.e. the yield per impacting atom increases).

ChemInform Abstract: Mechanism of the Reaction Between Iodate and Iodide Ions in Acid Solutions (Dushman Reaction).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Mechanism of the Reaction between Iodate and Iodide Ions in Acid Solutions (Dushman Reaction)

Evidence is given for a stepwise mechanism in the Dushman reaction by using accelerated-flow mixing to measure reaction rates at high [H+] and [I-], where pseudo-first-order rate constants vary from 213 to 6700 s-1. The typical [H+]2 dependence is lowered due to the formation of appreciable [HIO3]. The typical [I-]2 dependence is lowered because I2O2 is a steady-state intermediate. The rate expression is: −d[IO3]T/dt = k1(k2/k-1)KH[H+]2[I-]2[IO3]T/[(1 + KH[H+])(1 + (k2/k-1)[I-])], where k1 = 4.8 × 107 M-2 s-1, k2/k-1 = 2.3 M-1, and KH = 2.5 M-1 at μ = 0.50 M, 25 °C.

Mechanism of Reaction of the Hydrated Electron with Ozone, Perbromate, and Other Strongly Oxidizing Inorganic Oxocompounds

A model is proposed for the mechanism of reaction of the hydrated electron with strongly oxidizing inorganic oxocompounds, according to which such reactions comprise three steps: (1) a primary split-off of O- occurring immediately upon the transfer of the electron to the oxocompound, (2) after which O- becomes fully solvated, acquiring properties as in the bulk phase, and (3) finally, the solvated O- either escapes from the cage or forms an electron adduct by reacting back within the cage with its partner. The model is based on studies of the photochemistry of aqueous solution of the oxoanions O3- and ClO3- (Walhaut, P. K.; Silva, C.; Barbara, P. F. J. Phys. Chem. 1996, 100, 5188. Klaning, U. K.; Sehested, K. J. Phys. Chem. 1991, 95, 740.), which suggest that solvation of the photoproduct O- precedes cage-back reactions. Measurements of the reactions of the hydrated electron with the perbromate ion and the periodate ion and of the reactions of O- with the bromate and iodate ion support the model by verif...

Spectrophotometric determination of some vic-diol containing drugs using ion-exchange resins

Periodic acid and its salts have been widely used for the quantitative oxidation of vic-diol containing compounds including carbohydrates and catecholamine drugs. The advantage of using a polymeric resin (periodate form) over free periodate ions is that the resin quantitatively retains both unconsumed periodate ions and the iodate ions produced in the oxidation and, hence, enables one to undertake further studies on the structural, synthetic or preparative work. The resin (periodate form) was found to be a clean and sensitive chromogenic reagent for the spectrophotometric determination of some catecholamine drugs. The calibration graphs of absorption versus concentration in the range studied (5–50 ppm) were linear.

Theoretical investigation of hydrogen bonded water molecules in Ca(IO 3) 2·6H 2O

Routine quantum chemical calculations, possibly together with routine vibrational spectroscopic experiments, seem to yield more reliable OH bond lengths of crystal water molecules than routine neutron diffraction experiments. With OH being the different OH bonds in the crystal water molecules and H⋯O′ the nearly linear hydrogen bonds to adjacent iodate oxygens, the R OH- ω OH- R H⋯O′ variations have correlation coefficients better than 0.95. In contrast to infrared intensities, the Raman intensities are only moderately influenced by the crystal field. This supports the ‘oriented gas molecule model’ for estimating Raman intensities. The agreement between theoretical and measured intensities, however, is disappointing. This may indicate strong orbital interactions between the water molecules and the iodate and calcium ions.

Neutron Powder Diffraction Study on Highly Deuterated Ca(IO3)2.D2O

Neutron powder diffraction experiments were performed on highly deuterated calcium iodate monohydrate (bruggenite) to examine possible H/D enrichment effects. The title compound is built up of distorted CaO8 quadratic antiprisms. The iodate ions form layers parallel to (100), revealing relatively short interionic I⋯O distances of 3.02 and 2.90 Å. The water molecules are trigonally planar coordinated (2 IO3−, 1 Ca2+, site symmetry C1), forming asymmetric hydrogen bonds of different strength to adjacent iodate ions. Deviation from random distribution of the hydrogen atoms has been established.

Sequential Titrimetric and Spectrophotometric Determinations of Trace Amounts of Tin(II) and Tin(IV) by Amplification Reactions

Abstract Two simple and accurate titrimetric and spectrophotmetric methods have been developed for the determination of tin. The methods were based upon the oxidation of tin to tetravalent tin with sodium periodate at pH 2.2—3.5; excess periodate ions were then masked with 5% sodium molybdate at the same pH. The released iodate ions were determined spectrophotometry (at 350 nm) as triiodide after the addition of KI. This proposed procedure offered a six-fold amplification for each tin(II) ion. Alternatively, the released iodine was extracted with chloroform and shaken with an aqueous solution of 1% (w/v) sodium sulfite. The iodide ions produced in the aqueous phase were then oxidized with sodium periodate after removing the unreacted sodium sulfite by boiling with H2SO4 (2 M). The released iodate was finally determined by iodometry or spectrophotometry. This procedure offered 144-fold amplification per tin(II) ion. The determination of tin(IV) after prior reduction to tin(II) with sulfur dioxide was also found to be suitable. Analyses of the binary mixtures of tin(II)–tin(IV) in an aqueous solution, tin in organotin compounds and tin(II) and tin(IV) in artificial sea-waters were successfully carried out.

On-line electrochemical detection of carbohydrates coupled with the periodate oxidation

A new concept of an amplified electrochemical detection of carbohydrates is proposed, where carbohydrates are oxidized by periodate ion (IO 4 −) in acidic solutions to yield iodate ion (IO 3 −) which would be electrochemically reduced into iodide ion (I −) under suitable conditions. This scenario allows highly sensitive detection of carbohydrates, for example, as 30 electrons per aldohexose molecule. Our cyclic voltammetric study revealed that IO 3 − is reduced at much lower overpotentials than IO 4 − at gold, platinum and carbon-based electrodes despite the fact that the standard redox potential of the IO 3 −/I − couple is more negative than that of the IO 4 −/I − couple. In the electrochemical reduction of IO 3 −, I − is considered to function as a mediator. Stable flow-through detection of IO 3 − in the presence of IO 4 − was realized at glassy carbon electrodes. This method was coupled with the IO 4 − oxidation of carbohydrates and the experimental conditions were partially optimized on a flow injection system. The IO 4 − oxidation-coupled electrochemical detection of carbohydrates was applied to ligand-exchange high-performance liquid chromatography in a post-column mode. Sub-nanomole order of carbohydrates were successfully detected on this system.

Disproportionation Kinetics of Hypoiodous Acid As Catalyzed and Suppressed by Acetic Acid-Acetate Buffer.

The kinetics of the disproportionation of hypoiodous acid to give iodine and iodate ion (5HOI right harpoon over left harpoon 2I(2) + IO(3)(-) + H(+) + 2H(2)O) are investigated in aqueous acetic acid-sodium acetate buffer. The rate of iodine formation is followed photometrically at -log [H(+)] = 3.50, 4.00, 4.50, and 5.00, &mgr; = 0.50 M (NaClO(4)), and 25.0 degrees C. Both catalytic and inhibitory buffer effects are observed. The first process is proposed to be a disproportionation of iodine(I) to give HOIO and I(-); the iodide then reacts with HOI to give I(2). The reactive species (acetato-O)iodine(I), CH(3)CO(2)I, is postulated to increase the rate by assisting in the formation of I(2)O, a steady-state species that hydrolyzes to give HOIO and I(2). Inhibition is postulated to result from the formation of the stable ion bis(acetato-O)iodate(I), (CH(3)CO(2))(2)I(-), as buffer concentration is increased. This species is observed spectrophotometrically with a UV absorption shoulder (lambda = 266 nm; epsilon = 530 M(-)(1) cm(-)(1)). The second process is proposed to be a disproportionation of HOIO to give IO(3)(-) and I(2). Above 1 M total buffer, the reaction becomes reversible with less than 90% I(2) formation. Rate and equilibrium constants are resolved and reported for the proposed mechanism.

New insight into the potential oscillations during iodate reduction in alkaline solution

Potential oscillations during the reduction of iodate ions in alkaline solution under galvanostatic conditions have been re-investigated without adding iodide. The oscillations can take place only when the applied current is larger than the limiting current, and the oscillation amplitudes are within the plateau region of the limiting current. The bistability, i.e., iodate reduction and hydrogen evolution at different potentials, coupled with convection feedback, induced by hydrogen evolution, accounts for the oscillations. The mechanism was supported by the experimental results of current sweep and cyclic voltammetry. Our study shows that physical processes, i.e., alternately predominant mass transfer of the iodate by diffusion and by convection, play an important role in the oscillations.

Spectrophotometric determination of periodate or iodate ions by liquid-liquid extraction as an ion-pair using tetramethylammonium iodide

A simple and accurate extractive Spectrophotometric procedure was developed for the microdetermination of periodate and iodate in aqueous media. The determination of periodate was based upon the extraction of the ion-pair formed between the periodate and tetramethylammonium iodide at pH 4 in chloroform followed by direct Spectrophotometric measurements at 509, 358 and 288 nm. The optimum concentration range evaluated by Ringbom's plot, the molar absorptivity, the Sandell's sensitivity and the stoichiometry of the formed ion-pair were critically determined. Iodate could be determined quantitively by the proposed procedure after oxidation to periodate with potassium persulphate. The effect of the diverse ions on the determination of the periodate and/or iodate by the proposed procedures was also investigated. The application of the method for the analysis of iodate or periodate in the artificial fresh water was successfully carried out.