Determination of uranium in wet phosphoric acid by extraction with octylphenylphosphoric acid

A method for quantitative determination of uranium in phosphoric acid and wet phosphoric acid has been developed. After reduction with Fe, uranium(IV) is extracted with a kerosene solution of octylphenylphosphoric acid. The uranium was stripped with 10M H₃PO₄, containing H₂O₂, and then determined spectrophotometrically with Arsenazo III and by direct uranium(IV)-phosphoric acid solution measurements.     

Micelle-assisted cerium(IV) oxidation of <Emphasis Type="SmallCaps">L</Emphasis>-sorbose in aqueous sulfuric acid

Spectrophotometric kinetic technique has been used to investigate the effect of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) surfactants on the redox reaction of cerium(IV)+l-sorbose in aqueous sulfuric acid media. The anionic SDS has no effect, whereas the reaction rate increases in the presence of cationic CTAB, which is due to favorable conditions provide by the cationic micelles. The reaction rate decreases with [H₂SO₄], and no acid-dependent path has been observed. At constant [H₂SO₄], the rate of the reaction is dependent on the first powers of the l-sorbose and cerium(IV) concentrations. The CTAB-assisted reaction is retarded by addition of electrolytes (Na₂SO₄, NaNO₃, and NaCl), which is attributed to the competition between electrolyte anions and cerium(IV)-sulfato species. Bromide ion (of CTAB or externally added in the form of NaBr) is not oxidized by the cerium(IV) (as a main or side reaction).     

Kinetic study of the Ce(iii)- or Mn(ii)-catalyzed Belousov–Zhabotinsky reactions with mixed organic acid/ketone substrates

In a stirred batch reactor, the Ce(III)- or Mn(II)-catalyzed Belousov–Zhabotinsky reaction with mixed organic acid/ketone substrates exhibits oscillatory behavior. The organic acids studied here are: dl-mandelic acid (MDA), dl-4-bromomandelic acid (BMDA), and dl-4-hydroxymandelic acid (HMDA), and the ketones are: acetone (Me₂CO), methyl ethyl ketone (MeCOEt), diethyl ketone (Et₂CO), acetophenone (MeCOPh), and cyclohexanone ((CH₂)₅CO). The effects of bromate ion, organic acid, ketone, metal-ion catalyst, and sulfuric acid concentrations on the oscillatory patterns are investigated. Both conventional and stopped-flow methods are applied to study the kinetics of the oxidation reactions of the above organic acids by Ce(IV) or Mn(III) ion. The order of relative reactivities of the oxidation reactions of organic acids in 1 M H₂SO₄ is Mn(III)(SINGLEBOND)HMDA reaction>Ce(IV)(SINGLEBOND)HMDA reaction>Mn(III)(SINGLEBOND)BMDA, reaction>Mn(III)(SINGLEBOND)MDA reaction>Ce(IV)(SINGLEBOND)BMDA reaction>Ce(IV)(SINGLEBOND)MDA reaction. Spectrophotometric study of the bromination reactions of the above ketones shows that these reactions are zero-order with respect to bromine and first-order with respect to ketone and that ketone enolization is the rate-determining step. The order of relative rates of bromination or enolization reactions of ketones in 1 M H₂SO₄ is (CH₂)₅CO≫(MeCOEt, Et₂CO, Me₂CO)>MeCOPh. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet:30: 595–604, 1998     

Heterogeneous equilibrium between solution and slightly soluble compound in flow injection analysis: Platinum(IV) determination

Summary A new principle of flow injection analysis using a precipitation reaction is suggested. It is based on a change of the equilibrium between solution and slightly soluble compound when passing the solution studied through a reaction column, containing a slightly soluble compound. H₂PtCl₆ is determined with a column containing Tl₂PtCl₆. The detection is performed by the current of thallium(I) oxidation to thallium(III) on a platinum electrode. Two different flow injection schemes are used. The determination of platinum(IV) is applied to platinum analysis in spent industrial alumoplatinum catalysts.     

Photoinduced reactions of organic compounds with transition metal complexes. Communication 1. First example of substitution in the aromatic nucleus in photoexcitation of an electrophilic reagent: formation of σ-aryl complexes of Pt(IV) in the reaction of PtCl 6 2−2 with arenes

Conclusions The proposed mechanism of the photoinduced reaction of the PtCl ₆ ^2– ion with an arene in acetic or aqueous trifluoroacetic acid, completed by the formation of a platinum (IV) -aryl complex, includes a stage of electron transfer from the arene to platinum(IV) and the formation of an ion radical pair which is then transformed into a Wheland complex.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2681–2687, December, 1984.     

Studies on the solvent extraction behaviour of Pu(IV) from sulfuric acid medium into di-2-ethylhexyl phosphoric acid (HDEHP)

Extraction of plutonium(IV) from aqueous sulfuric and sulfuric-nitric acid into di-2-ethylhexyl phosphoric acid (HY) in the diluents n-dodecane, toluene or chloroform has been investigated. The composition of the Pu(IV) species extracted from H₂SO₄ was found to be PuH₂Y₆, which changed to Pu(NO₃)H₂Y₅ and Pu(NO₃)₂H₂Y₄ with increasing concentration of nitrate ion in the aqueous medium. These three species can be represented as PuY₂(HY₂)₂, Pu(NO₃)Y(HY₂)₂ and Pu(NO₃)₂(HY₂)₂, respectively, where Y represents the anion of monomeric HY, and HY₂ the anion of dimeric H₂Y₂. Synergism in the extraction of Pu(IV) by the addition of thenoyltrifluoroacetone (HTTA) to HY was also investigated and attributed to extraction of the additional species, Pu(TTA)Y(HY₂)₂ and Pu(TTA)₂(HY₂)₂. The addition of the neutral extractant tri-n-octylphosphine oxide (TOPO) to HY did not result in synergism in the extraction of Pu(IV) from aqueous sulfuric acid. With aqueous nitric acid under similar conditions, however, synergism was observed. The possible equilibria in these systems were identified and the corresponding equilibrium constants were determined.     

Mechanistic study of cerium(IV) oxidation of antimony(III) in aqueous sulphuric acid in the presence of micro amounts of manganese(II) by stopped flow technique

The oxidation of antimony(III) by cerium(IV) has been studied spectrometrically (stopped flow technique) in aqueous sulphuric acid medium. A minute amount of manganese(II) (10⁻⁵ mol dm⁻³) is sufficient to enhance the slow reaction between antimony(III) and cerium(IV). The stoichiometry is 1:2, i.e. one mole of antimony(III) requires two moles of cerium(IV). The reaction is first order in both cerium(IV) and manganese(II) concentrations. The order with respect to antimony(III) concentration is less than unity (ca 0.3). Increase in sulphuric acid concentration decreases the reaction rate. The added sulphate and bisulphate decreases the rate of reaction. The added products cerium(III) and antimony(V) did not have any significant effect on the reaction rate. The active species of oxidant, substrate and catalyst are Ce(SO₄)₂, [Sb(OH)(HSO₄)]⁺ and [Mn(H₂O)₄]²⁺, respectively. The activation parameters were determined with respect to the slow step. Possible mechanisms are proposed and reaction constants involved have been determined.     

Synthesis and Analysis of the Structure,Diffusion and Cytotoxicity of Heterocyclic Platinum(IV) Complexes

We have developed six dihydroxidoplatinum(IV) compounds with cytotoxic potential. Each derived from active platinum(II) species, these complexes consist of a heterocyclic ligand (H_L) and ancillary ligand (A_L) in the form [Pt(H_L)(A_L)(OH)₂]²⁺, where H_L is a methyl‐functionalised variant of 1,10‐phenanthroline and A_L is the S,S or R,R isomer of 1,2‐diaminocyclohexane. NMR characterisation and X‐ray diffraction studies clearly confirmed the coordination geometry of the octahedral platinum(IV) complexes. The self‐stacking of these complexes was determined using pulsed gradient stimulated echo nuclear magnetic resonance. The self‐association behaviour of square planar platinum(II) complexes is largely dependent on concentration, whereas platinum(IV) complexes do not aggregate under the same conditions, possibly due to the presence of axial ligands. The cytotoxicity of the most active complex, exhibited in several cell lines, has been retained in the platinum(IV) form.     

Insertion of SnCl2 into Pt–Cl bonds: synthesis and characterization of four- and five-coordinate trichlorostannylplatinum(II) complexes

Reaction of platinum(IV) chloride with SnCl₂?·?2H₂O in the presence of [NHR₃]₃Cl (R?=?Me, Et) in 3M hydrochloric acid affords the anionic five-coordinate platinum(II) complexes [NHR₃]₃[Pt(SnCl₃)₅], R?=?Me (1), Et (2), respectively. Moreover, platinum(IV) chloride reacts with SnCl₂?·?2H₂O in the presence of bis(triphenylphosphoranylidene)ammonium chloride in acetone/dichloromethane to form [N(PPh₃)₂]₃[Pt(SnCl₃)₅] (3). In contrast, reaction of an acetone solution of platinum(IV) chloride with SnCl₂?·?2H₂O in the presence of bis(triphenylphosphoranylidene) ammonium chloride resulted in the formation of cis-[N(PPh₃)₂]₂[PtCl₂(SnCl₃)₂] (4). The same products are obtained by using a platinum(II) salt as starting material. Similarly, cis and trans- dichlorobis(diethyl sulfide)platinum(II) reacts with SnCl₂?·?2H₂O in 5M hydrochloric acid to give [PtCl(SEt₂)₃]₃[Pt(SnCl₃)₅] (5) by facile insertion of SnCl₂ into the Pt–Cl bond. However, treatment of an acetone solution of cis- and trans-[PtCl₂(SEt₂)₂] with SnCl₂?·?2H₂O in the presence of a small amount of HCl resulted in the formation of 5, which dissociates in solution to give [PtCl₂(SEt₂)₂]. The complexes have been fully characterized by elemental analysis and multinuclear NMR (¹H,?¹³C,?¹⁹⁵Pt,?¹¹⁹Sn) spectroscopy. A structure determination of crystals grown from a solution of 2 by X-ray diffraction methods shows that platinum adopts a regular trigonal bipyramidal geometry.     

The separation of palladium and platinum by ion flotation

Differences in the ion flotation properties of palladium(II) and platinum(IV) chloro complexes in aqueous solutions are used to achieve separations of these metals. The anionic chloro complex PtCl^2-₆ is floated selectively with cationic surfactants of the type, RNR'₃Br, from solutions of PdCl^2-₄ and various concentrations of hydrochloric acid. The palladium(II) does not float from solutions of ? 3.0 M HCl and the platinum(IV) floated from these solutions can be recovered free of palladium. However, the separation is incomplete as much of the platinum(IV) is also unfloated from these solutions. Quantitative separations are obtained by conversion of the palladium(II) to the cationic ammine, Pd(NH₃)₄²⁺ with aqueous ammonia prior to flotation. The anionic chloro complex of platinum(IV) is unaffected by the presence of ammonia and is floated quantitatively with the surfactant n-hexadecyltri-n-propylammonium bromide from 0.01 M ammonia solutions.     

Hydrogen‐bonded structures of the 1:1 and 1:2 compounds of chloranilic acid with pyrrolidin‐2‐one and piperidin‐2‐one

In the four compounds of chloranilic acid (2,5‐dichloro‐3,6‐dihydroxycyclohexa‐2,5‐diene‐1,4‐dione) with pyrrolidin‐2‐one and piperidin‐2‐one, namely, chloranilic acid–pyrrolidin‐2‐one (1/1), C₆H₂Cl₂O₄·C₄H₇NO, (I), chloranilic acid–pyrrolidin‐2‐one (1/2), C₆H₂Cl₂O₄·2C₄H₇NO, (II), chloranilic acid–piperidin‐2‐one (1/1), C₆H₂Cl₂O₄·C₅H₉NO, (III), and chloranilic acid–piperidin‐2‐one (1/2), C₆H₂Cl₂O₄·2C₅H₉NO, (IV), the shortest interactions between the two components are O—H...O hydrogen bonds, which act as the primary intermolecular interaction in the crystal structures. In (II), (III) and (IV), the chloranilic acid molecules lie about inversion centres. For (III), this necessitates the presence of two independent acid molecules. In (I), there are two formula units in the asymmetric unit. The O...O distances are 2.4728 (11) and 2.4978 (11) Å in (I), 2.5845 (11) Å in (II), 2.6223 (11) and 2.5909 (10) Å in (III), and 2.4484 (10) Å in (IV). In the hydrogen bond of (IV), the H atom is disordered over two positions with site occupancies of 0.44 (3) and 0.56 (3). This indicates that proton transfer between the acid and base has partly taken place to form ion pairs. In (I) and (II), N—H...O hydrogen bonds, the secondary intermolecular interactions, connect the pyrrolidin‐2‐one molecules into a dimer, while in (III) and (IV) these hydrogen bonds link the acid and base to afford three‐ and two‐dimensional hydrogen‐bonded networks, respectively.     

Manganese(II) catalysed oxidation of glycerol by cerium(IV) in aqueous sulphuric acid medium: a kinetic and mechanistic study

The manganese(II) catalysed oxidation of glycerol by cerium(IV) in aqueous sulphuric acid has been studied spectrophotometrically at 25 °C and I = 1.60 mol dm⁻³. Stoichiometry analysis shows that one mole of glycerol reacts with two moles of cerium(IV) to give cerium(III) and glycolic aldehyde. The reaction is first order in both cerium(IV) and manganese(II), and the order with respect to glycerol concentration varies from first to zero order as the glycerol concentration increases. Increase in sulphuric acid concentration, added sulphate and bisulphate all decrease the rate. Added cerium(III) retards the rate of reaction, whereas glycolic aldehyde had no effect. The active species of oxidant and catalyst are Ce(SO₄)₂ and [Mn(H₂O)₄]²⁺. A mechanism is proposed, and the reaction constants and activation parameters have been determined.     

Ruthenium(III)‐mediated oxidation of D‐mannitol by cerium(IV) in aqueous sulfuric acid medium: A kinetic and mechanistic approach

The oxidation of D ‐mannitol by cerium(IV) has been studied spectrophotometrically in aqueous sulfuric acid medium at 25°C at constant ionic strength of 1.60 mol dm^?3. A microamount of ruthenium(III) (10^?6 mol dm^?3) is sufficient to enhance the slow reaction between D ‐mannitol and cerium(IV). The oxidation products were identified by spot test, IR and GC‐MS spectra. The stoichiometry is 1:4, i.e., [D ‐mannitol]: [Ce(IV)] = 1:4. The reaction is first order in both cerium(IV) and ruthenium(III) concentrations. The order with respect to D ‐mannitol concentration varies from first order to zero order as the D ‐mannitol concentration increases. Increase in the sulfuric acid concentration decreases the reaction rate. The added sulfate and bisulfate decreases the rate of reaction. The active species of oxidant and catalyst are Ce(SO₄)₂ and [Ru(H₂O)₆]³⁺, respectively. A possible mechanism is proposed. The activation parameters are determined with respect to a slow step and reaction constants involved have been determined. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 440–452, 2010     

Kinetics of oxidative degradation of pantothenic acid by cerium(IV) in aqueous perchloric acid

The kinetics of oxidation of pantothenic acid (PA), Me₂C(CH₂OH)CH(OH)C(O)NHCH₂CH₂CO₂H, by cerium(IV) in aqueous HClO₄ medium at constant ionic strength, 2.0 mol dm^–3, has been studied spectrophotometrically. The reaction showed first-order kinetics in Ce^IV concentration, an apparent less than unit order dependence in [PA] and an inverse fractional order in [H⁺]. Initial addition of products had no significant effect on the rate of the reaction. A possible mechanism is proposed, and the reaction constants involved in the mechanism have been computed. There is good agreement between the observed and calculated rate constants under different experimental conditions. The activation parameters were calculated with respect to the slow step of the proposed mechanism.     

Electrochemical reduction of 5,5′-dichlorohydurilic acid. mechanism and analytical applications

The electrochemical reduction of 5,5′-dichlorohydurilic acid has been studied at the dropping mercury electrode (DME) and the pyrolytic graphite electrode (PGE). At the DME the single polarographic reduction wave observed at pH 6–11 involves a direct 4e—2H⁺ reduction of the carbon-halogen bond to give hydurilic acid and chloride. The state of hydration or ionization of the 5,5′-dichlorohydurilic acid has no effect on the electrochemical reaction. At the PGE, 5,5′-dichlorohydurilic acid shows two voltammetric peaks. Peak I_c, observed between pH 5 and 7, arises from an overall 4e—2H⁺ reduction of 5,5′-dichlorohydurilic acid via a mechanism that involves initial electron attack at a carbonyl group alpha to a carbon-halogen bond with simultaneous elimination of chloride ion. The peak II_c process involves an initial 2e—1H⁺ reduction of a partially hydrated form of 5,5′-dichlorohydurilic acid with only one unhydrated halocarbonyl moiety available for reaction. Attack is again via the carbonyl group with simultaneous elimination of chloride and formation of 5-chlorohydurilic acid. A chemical dehydration step then occurs with a rate constant of ca. 0.24 s^?1 at pH 8.2, with formation of a further reducible halocarbonyl group. This is again reduced in an overall 2e—2H⁺ reaction to give hydurilic acid and chloride ion. The peak II_c process hence proceeds via an ECE mechanism. The different mechanisms observed for reduction of 5,5′-dichlorohydurilic acid at mercury and pyrolytic graphite electrodes are unusual. Analytical methods have been developed for the polarographic determination of 5,5′-dichlorohydurilic acid via its reduction wave at the DME, and for the voltammetric determination of hydurilic acid via its first oxidation peak at the PGE.     

Chemihiminescence by the interaction of XeO3 and the products of photolysis of uranyl solutions in sulfuric acid

Using the chemiluminescence oxidation of U(IV) and H₂O₂ with xenon trioxide as a model, it has been found that during the photolysis of solutions of UO₂SO₄ in sulfuric acid in the absence of any organic compounds, the accumulation of U(SO₄)₂ and H₂O₂ takes place as a result of the reaction of the primary products of the photoreduction of uranyl ion,i.e., UO₂ ⁺ and the OH radical.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 751–754, April, 1994.The work was financially supported by the Russian Foundation for Basic Research, Project 93-03-12291.     

Kinetic study of the Ce(III)‐, Mn(II)‐ or Fe(phen)32+‐catalyzed Belousov–Zhabotinsky reaction with ethyl hydrogen malonate

In a stirred batch reaction, Fe(phen)₃²⁺ ion behaves differently from Ce(III) or Mn(II) ion in catalyzing the bromate‐driven oscillating reaction with ethyl hydrogen malonate [CH₂COOHCOOEt, ethyl hydrogen malonate (EHM)]. The effects of N₂ atmosphere, concentrations of bromate ion, EHM, metal ion catalyst, sulfuric acid, and additive (bromide ion or bromomalonic acid) on the pattern of oscillations were investigated. The kinetic study of the reaction of EHM with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion indicates that under aerobic or anaerobic conditions the order of reactivity toward reacting with EHM is Mn(III) > Ce(IV) ≫ Fe(phen)₃³⁺, which follows the same trend as that of the malonic acid system. The presence of the ester group in EHM lowers the reactivity of the two methylene hydrogen atoms toward bromination or oxidation by Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion. No good oscillations were observed for the BrO₃₋‐CH₂(COOEt)₂ reaction catalyzed by Ce(III), Mn(II), or Fe(phen)₃²⁺ ion. A discussion of the effects of oxygen on the reactions of malonic acid and its derivatives (RCHCOOHCOOR′) with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion is also presented. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 52–61, 2000     

Novel platinum(II) and (IV) complexes of naphthaldimine schiff bases

Naphthaldimines containing N₂O₂ donor centers react with platinum(II) and (IV) chlorides to give two types of complexes depending on the valence of the platinum ion. For [Pt(II)], the ligand is neutral, [(H₂L¹)PtCl₂]·3H₂O (1) and [(H₂L³)₂Pt₂Cl₄]·5H₂O (3), or monobasic [(HL²)₂Pt₂Cl₂]·2H₂O (2) and [(HL⁴)₂Pt]·2H₂O (4). These complexes are all diamagnetic having square-planar geometry. For [Pt(IV)], the ligand is dibasic, [(L¹)Pt₂Cl₄(OH)₂]·2H₂O (5), [(L²)Pt₃Cl₁₀]·3H₂O (6), [(L³)Pt₂Cl₄(OH)₂]·C₂H₅OH (7) and [(L⁴)Pt₂Cl₆]·H₂O (8). The Pt(IV) complexes are diamagnetic and exhibit octahedral configuration around the platinum ion. The complexes were characterized by elemental analysis, UV-Vis and IR spectra, electrical conductivity and thermal analyses (DTA and TGA). The molar conductances in DMF solutions indicate that the complexes are non-ionic. The complexes were tested for their catalytic activities towards cathodic reduction of oxygen.     

Kinetics of reaction of alkynes with some cobalt carbonyls

Pt(CO)₂Cl₂ reacts in benzene, toluene or tetrahydrofuran with 3-hexyne to give carbonylplatinumbis[di-μ-chloro,chloro(tetraethylcyclobutadiene)platinum](I), bis[dichloro(tetraethylcyclopentadienone)platinum] (III), dichloro-(tetraethyl-p-benzoquinone)platinum (IV) and dichloro(tetraethylcyclobutadiene)platinum (II). This last compound is also obtained by treating I with 1 to 3 moles of triphenylphosphine or p-toluidine. p ]The structure and reactions of III are discussed; the anion exchange reaction gives the iodo-analogue, while treatment with donor ligands gives adducts of formula [(C₂H₅)₄C₄CO]PtCl₂L(L = triphenylphosphine, p-toluidine, benzylamine and pyridine) and [(C₂H₅)₄C₄CO]PtCl₂L₂(L = benzylamine, 3-methylpyridine). p ]2-Butyne reacts with dichlorodicarbonylplatinum to give the methyl analogous of compounds I–III.     

Cu(II) catalyzed reaction between phenyl hydrazine and toluidine blue—dual role of acid

The detailed kinetics of Cu(II) catalyzed reduction of toluidine blue (TB⁺) by phenyl hydrazine (Pz) in aqueous solution is studied. Toluidine white (TBH) and the diazonium ions are the main products of the reaction. The diazonium ion further decomposes to phenol (PhOH) and nitrogen. At low concentrations of acid, H⁺ ion autocatalyzes the uncatalyzed reaction and hampers the Cu(II) catalyzed reaction. At high concentrations, H⁺ hinders both the uncatalyzed and Cu(II) catalyzed reactions. Cu(II) catalyzed had stoichiometry similar to the uncatalyzed reaction, Pz+2 TB⁺+H₂O=PhOH+2 TBH+2 H⁺+N₂. Cu(II) catalyzed reaction occurs possibly through ternary complex formation between the unprotonated toluidine blue and phenyl hydrazine and catalyst. The rate coefficient for the Cu(II) catalyzed reaction is 2.1×10⁴ M⁻² s⁻¹. A detailed 13‐step mechanistic scheme for the Cu(II) catalyzed reaction is proposed, which is supported by simulations. © 1999 John Wiley & Sons, Inc., Int J Chem Kinet 31: 271–276, 1999