Transition metals in atmospheric aqueous samples, analytical determination and speciation

Summary Two rain water samples were analyzed with respect to the determination of the species which are present at the given conditions. The parameters determined were: pH, E_h, electrolytical conductivity, concentration of anions (SO ₄ ^2– , NO ₃ ^– , Cl^–, NO ₂ ^– , HCOO^–, CH₃COO^–), of main cations (Na⁺, K⁺, NH ₄ ⁺ , Mg²⁺, Ca²⁺), and of transition metals (V, Cr, Mn, Fe, Co, Cu, Zn). The methods used were filtration and ultrafiltration, voltammetry, sorption on various sorbents and ion chromatography. Furthermore, E_h-pH-diagrams were taken into account and the partition of the species was calculated by means of stability constants. The transition elements species in the atmospheric aqueous solutions are discussed.     

Marked variations of proton release energy of the G–M (M = Li, Na) in the water circumstance

The variations of N1–H proton release energy of G–M (M = Li, Na) cation have been investigated employing density functional theory using B3LYP/6-31++G^**//B3LYP/6-31+G^* method. There are three modes (NO mode, N mode and O mode) when the hydrated-M⁺ bonds to guanine. The bonding energy of the hydrated M⁺ to the guanine reduces following the increase in the number of water molecules. The proton release energies of the G–M⁺ complexes are calculated at the condition of the different numbers of water molecules and the different modes of water molecules bonded on the G–M⁺. The results show that the difference of proton release energy on three modes is very small, and the proton release energies of the Na⁺ complexes are slightly larger than those of the Li⁺ complexes. The effect on the N1–H proton release is very small when the water molecules bond on the M⁺ cation, but the effect is very large when the water molecule bonds on the N1–H proton and the proton releases as the hydrated proton. The IR vibrational frequencies of the hydrated G–M⁺ complexes are calculated using analytic second derivative methods at the B3LYP/6-31+G^* level. The vibrational frequency analyses show that the changes of the vibrational frequency are consistent with the changes of geometry and the changes of the N1–H proton release energy. The N1–H proton release (N1–H proton release energy: 45–60 kcal/mol) of the guanine occurs easily under the biological environment.     

Solvent Extraction–Photometric Determination of Palladium Using Complexation with 1-(2-Pyridylazo)-2-Naphthol

Palladium(II) complexation with 1-(2-pyridylazo)-2-naphthol (PAN) in aqueous solutions followed by extraction with chloroform and photometric detection was studied. The best conditions were found for the formation of the complex in an aqueous solution and for its extraction with chloroform that provided a sufficient degree of binding palladium ions. The stability constant of the complex cation PdX⁺, which is extracted by chloroform as an ion pair [PdX]⁺[An^–] (An^–– CH₃COO^–), was calculated using the methods proposed by Rossotti (log K _stab= 18.73) and Komar' (log K _stab= 18.82). The equilibrium constant of the complexation reaction was also calculated (5.45 × 10⁴). It was shown that components of nonferrous alloys affect the determination of palladium by photometry as its complex or ion pair with PAN in chloroform.     

Coadsorption of Tetraalkylammonium Cations and Halide Anions on the Uncharged Surface of Mercury Electrode

The data on coadsorption of tetraethylammonium (Et₄N⁺), tetrapropylammonium (Pr₄N⁺), and tetrabutylammonium (Bu₄N⁺) cations with Cl^–, Br^–, and I^– anions on an uncharged mercury electrode are compared with the models of coadsorption in a common monolayer and two parallel layers. The second model is shown to be in best agreement with experimental isotherms. However, the least discrepancy between calculations and experimental results is obtained when coadsorption of mentioned cations and anions is described by the Frumkin isotherm for neutral molecules with certain effective adsorption parameters.     

Kinetics and mechanism of the oxidation of thiosulphate by hexachloroplatinate(IV)

Summary Rate constants for the oxidation of thiosulphate by hexachloroplatinate(IV) have been measured. The kinetics of the oxidation of thiosulphate follow a second-order rate law, first order with respect to thiosulphate and first order with respect to platinum(IV). The influence of pH is small. The rates are found to depend on the nature and concentration of the cations and follow the order: Cs⁺>Rb⁺>K⁺>Na⁺>Li⁺. The activation parameters calculated from the temperature studies are: H=42.9 k J mol^–1 and S=–102 JK^–1 mol^–1. A mechanism of the reaction in terms of intermediate formation of free radicals followed by the formation of tetrathionate is postulated to explain the kinetic behaviour.     

Determination of copper(I)-ethylene complexes, [Cu(C2H4)]+ and [Cu(C2H4)2]+, with aid of EDTA titration of copper(I) and copper(II) ions

Summary Volumetric measurements of ethylene and simple EDTA titration of copper(I) and copper(II) ions confirm that [CuL]⁺ and [CuL₂]⁺ are formed when an aqueous solution of copper(II) is reduced by copper metal in the presence of ethylene, (L). The formation constants,K ₁=[CuL⁺]²[Cu²⁺]^–1[L]^–2 andK ₂=[CuL ₂ ⁺ ]^–1[L]^–1, have been estimated. The formation of [CuL]⁺ is accompanied by an enthalpy change, H, of –25 kJ mol^–1, and a positive entropy change, S, of 13 J mol^–1 K^–1.     

Synthesis,stability and reactivity of cationic carbonyl complexes of rhodium(I)

Summary Trans-[RhCl(CO)L₂] (L = PPh₃, AsPh₃ or PCy₃) react with AgBF₄ in CH₂Cl₂ to give the novel species [Rh-(CO)L₂]⁺ [BF₄]^–.nCH₂Cl₂ (n = 1/2 or 1 1/2) (1–3), which we believe to be stabilised by weak solvent interaction. The corresponding stibine compound cannot be isolated by the same process, instead [Rh(CO)₂(SbPh₃)₃]⁺ [BF₄]^– (7) is formed when the reaction is carried out in the presence of CO. When reactions designed to prepare [Rh(CO)L₂]⁺ [BF₄]^– are performed in the presence of CO, or [Rh(CO)L₂]⁺ [BF₄]^– complexes are reacted with CO, [Rh(CO)₂L₂]⁺ [BF₄]^– (L = PPh₃, AsPh₃ or PCy₃) (4–6) are formed. If Me₂CO is used as solvent in the preparation of [Rh(CO)L₂]⁺ [BF₄]^– (L = PPh₃ or AsPh₃), then the products are the four-coordinate [Rh(CO)L₂-(Me₂CO)]⁺ [BF₄]^– (8,9) species. The complexes have been characterised by i.r., ³¹P and ¹H n.m.r. spectroscopy and elemental analyses.     

Thermodynamics of complexation of zinc(II) with chloride,bromide and iodide ions in hexamethylphosphoric triamide

The complexation of zinc(II) with chloride, bromide and iodide ions has been studied by calorimetry in hexamethylphosphoric triamide (HMPA) containing 0.1 mol-dm^–3 (n-C₄H₉)₄NClO₄ as a constant ionic medium at 25°C. The formation of [ZnX_n]^(2–n)+ (n=1,2,3,4 for X=Cl; n=1,2 for X=Br, I) is revealed, and their formation constants, enthalpies and entropies were determined. It is proposed that the zinc(II) ion is fourcoordinated in HMPA and the coordinating HMPA molecules are stepwise replaced with halide ions to form [ZnX_n(hmpa)_4–n]^(2–n)+ (n=1–4), as is the case for the cobalt(II) ion. Furthermore, the formation of [ZnClI], [ZnBrI], [ZnBrCl] and [ZnBrCl₂]^– is revealed in the relevant ternary systems. It is found that the affinity of a given halide ion X^– to [ZnCl]⁺, [ZnBr]⁺ and [Znl]⁺ is practically the same.     

Kinetics and mechanism of formation of tetrachloropalladate(II) in the reactions of bis(oxalato)- and bis(malonato) palladate(II) with chloride in acid media

Summary Kinetics of formation of [PdCl₄]^2– from [Pd(ox)₂]^2– and [Pd(mal)₂]^2– has been studies in aqueous acid media in the presence of an excess of chloride ion by stopped-flow spectrophotometry. Both the complexes undergo the transformation in two well separated consecutive steps. In 0.02–0.05 M acid with 0.2 M Cl^–, Pd(AA)^2– dissociates leading to the formation of [Pd(AA)Cl₂]^2– (where AA =ox^2– or mal^2–), which in 0.1–0.6 M acid and 1 M Cl^– forms [PdCl₄]^2– in a relatively slow step. For both steps k_abs=k₀+k₂[H⁺][Cl^–]. Activation parameters corresponding to k₀ and k₂ have been determined. Results indicate that [Pd(mal)₂]^2– is much more labile to substitution than [Pd(ox)₂]^2– and for both the lability is far greater than that of [Pd(bigH)₂]²⁺ and [Pt(ox)₂]^2– reported earlier.     

Preparation,Characterization and Standard enthalpy of formation of Sr2CeO4.

Sr₂CeO₄ has been prepared by sol-combustion and co-precipitate routes and the resulting products have been characterized by XRD analysis. The molar enthalpies of solution of Sr₂CeO₄(s), Sr(NO₃)₂(s) and Ce(NO₃)₃·6H₂O(s) in 0.150 dm^–3 of (4.41 mol dm–3 H₂O₂+4.23 mol dm^–3 of HNO₃) solvent as well as the molar enthalpies of solution of Sr₂CeO₄(s), SrCl₂(s) and CeCl₃(s) in 0.150 dm³ of (1.47 mol dm^–3 H₂O₂+3.05 mol dm^–3 of HClO₄) solvent have been measured using an isoperibol type calorimeter. From these results and other auxiliary data, the standard molar enthalpy of formation of Sr₂CeO₄ has been derived to be –2277.3±3.1 kJ mol^–1 at 298.15 K. This is the first reported thermodynamic data on this compound.     

Synergistic solvent extraction of lanthanides with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one and aliphatic amines: Influence of the ammonium salt ions

Summary The synergistic solvent extraction of Pr, Gd, and Yb with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one (HP) and tridodecylammonium (TDAHA), trioctylammonium (TOAHA), and dioctylammonium (DOAHA) salts (A ^–=Cl^–, NO ₃ ^– , and ClO ₄ ^– ) in C₆H₆ has been studied. The composition of the extracted species has been determined asAmH⁺[LnP ₄]^– (AmH⁺: ammonium salt cation). The values of the equilibrium constant have been calculated. The influence of the ammonium salt ions on the extraction process is discussed.

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Synergetische Extraktion von Lanthaniden mit Mischungen aus 1-Phenyl-3-methyl-4-benzoyl-pyrazol-5-on und aliphatischen Aminen: Einfluß der Ammoniumsalzionen

Zusammenfassung Die synergetische Extraktion von Pr, Gd und Yb mit Mischungen aus 1-Phenyl-3-methyl-4-benzoyl-pyrazol-5-on (HP) und Tridodecylammonium-(TDAHA), Trioctylammonium-(TOAHA) und Dioctylammoniumsalzen (DOAHA) (A ^–=Cl^–, NO ₃ ^– und ClO ₄ ^– ) in C₆H₆ wurde untersucht. Die Zusammensetzung der Extraktionskomplexverbindungen wurde zuAmH⁺[LnP ₄]^– bestimmt; die Gleichgewichtskonstanten wurden berechnet. Der Einfluß der Ionen des Ammoniumsalzes auf die Extraktion wird diskutiert.

     

Comparison of temperature,pressure and isotope effects on the proton jump between the hydroxide and oxonium ion

The limiting molar conductances ° of potassium deuteroxide KOD in D₂O and potassium hydroxide KOH in H₂O were determined at 5 and 45°C as a function of pressure to clarify the difference in the temperature, pressure and isotope effects on the proton jump between an OD^– (OH^–) and a D₃O⁺ (H₃O⁺) ion. The excess conductances of the OD^– ion in D₂O and the OH^– ion in H₂O, _E ⁰ (OD^-) and _E ⁰ (OH^-), increase with increasing temperature and pressure as in the case of the excess deuteron and proton conductances, _E ⁰ (D⁺) and _E ⁰ (H⁺). However, the temperature effect on the excess conductance is larger for the OD^–(OH^–) ion than for the D₃O⁺ (H₃O⁺) ion but the pressure effect is much smaller for the OD^– (OH^–) ion than for the D₃O⁺ (H₃O⁺) ion. These findings are correlated with larger activation energies and less negative activation volumes found for the OD^– (OH^–) ion than for the D₃O⁺ (H₃O⁺) ion. Concerning the isotope effect, the value of _E ⁰ (OH^-)/ _E ⁰ (OD^-) deviates considerably from at each temperature and pressure in contrast with that of _E ⁰ (H⁺)/ _E ⁰ (D⁺), although both of them decrease with increasing temperature and pressure. These results are discussed mainly in terms of the difference in repulsive force between the OD^– (OH^–) or the D₃O⁺ (H₃O⁺) ion and the adjacent water molecule, the difference in strength of hydrogen bonds in D₂O and H₂O, and their variations with temperature, pressure, and isotope.     

A reinvestigation of the gas phase reaction of boron atoms, B(Pj)/B(Pj) with acetylene,

The reaction dynamics of ground state boron atoms, B(²P_j), with acetylene, was reinvestigated and combined with novel electronic structure calculations. Our study suggests that the boron atom adds to the carbon–carbon triple bond of the acetylene molecule to yield initially a cyclic intermediate undergoing two successive hydrogen atom migrations to form ultimately an intermediate i3. The latter was found to decompose predominantly to the c-BC₂H(X²A′) isomer plus atomic hydrogen via a tight exit transition state. To a minor amount, an isomerization of i3–i4 prior to a hydrogen atom ejection forming the linear structure, HBCC(X¹Σ⁺), has to be taken into account. Since the c-BC₂H(X²A′) and HBCC(X¹Σ⁺) isomers are separated by an isomerization barrier to ring closure of only 3 kJ mol⁻¹, internally excited HBCC(X¹Σ⁺) products can isomerize to the c-BC₂H(X²A′) structure and vice versa.     

Activation Parameters for the Formation and Decay of Partial-Charge-Transfer Exciplexes of 9-Cyanoanthracene, 1,12-Benzperylene, and Pyrene

The factors affecting the rate of formation and decay of exciplexes with partial charge transfer, which form in the kinetic region of photoinduced electron transfer (G ^* _et > –0.2 eV), were studied. The rate of formation of exciplexes is controlled mainly by the diffusion of reactants and the low steric factor (0.15–1.0). The activation enthalpy and entropy for the exciplex formation (9–13 kJ mol^–1 and –(12–28) J mol^–1 K^–1) are close to the activation enthalpy and entropy of diffusion, respectively. Charge transfer in an exciplex and polarization of the medium generally occur after passing the transition state. In contrast, the activation enthalpy of exciplex decay (its conversion into the reaction products) is close to zero (±6 kJ mol^–1) and the activation entropy is strongly negative –(80–130) J mol^–1 K^–1.     

Bromokomplexe von Co(II) und Ni(II) in Acetonitril,Propandiol-1,2-carbonat und Trimethylphosphat

Zusammenfassung Die Bildung von Bromokomplexen von Co(II) und Ni(II) wird in Acetonitril (AN), Propandiol-1,2-carbonat (PDC) und Trimethylphosphat (TMP) auf spektrophotometrischem, potentiometrischem und konduktometrischem Wege untersucht. Folgende Koordinationsformen dürften vorliegen: [CoBr]⁺ (oktaedrisch inAN undTMP), CoBr₂ (tetraedrisch inAN, oktaedrisch inTMP), [CoBr₃]^– (tetraedrisch inAN, oktaedrisch inTMP), [CoBr₄]^2– (tetraedrisch inAN undPDC, oktaedrisch inTMP), [NiBr]⁺ (oktaedrisch inAN), NiBr₂ (tetraedrisch inAN, oktaedrisch inTMP), [NiBr₃]^– (tetraedrisch inAN), [NiBr₄]^2– (tetraedrisch inAN undPDC, oktaedrisch inTMP).

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The formation of bromo complexes of Co(II) and Ni(II) is investigated in acetonitrile (AN), propanediol-1,2-carbonate (PDC) and trimethylphosphate (TMP) by spectrophotometric, potentiometric and conductometric methods. The following coordination forms are reported: [CoBr]⁺ (octahedral inAN andTMP), CoBr₂ (tetrahedral inAN, octahedral inTMP), [CoBr₃]^– tetrahedral inAN, octahedral inTMP), [CoBr₄]^2– (tetrahedral inAN andPDC, octahedral inTMP), [NiBr]⁺ (octahedral inAN), NiBr₂ (tetrahedral inAN, octahedral inTMP), [NiBr₃]^– (tetrahedral inAN), [NiBr₄]^2– (tetrahedral inAN andPDC, octahedral inTMP).

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Mit 8 Abbildungen     

Complexes between disubstituted benzo-15-crown-5 ligands and sodium or potassium bromides

Stability constants have been determined with ion selective electrodes for complexes between sodium or potassium bromide in methanol with each of four crown ethers, benzo-15-crown-5 (Ia), dibromobenzo-15-crown-5 (Ib), dimethoxybenzo-15-crown-5 (Ic) and di-n-butoxybenzo-15-crown-5 (Id). Those for (Ib) were significantly lower than the others. The stability constants for complexes between sodium bromide and (Ia) and (Ib) in dimethylformamide (DMF) were found to be about one fifth of the corresponding values in methanol. The conductivity method was used to measure the ion pairing in methanol of sodium bromide alone and in the presence of (Ia), (Ib), or (Ic). Ion pairing is increased on complexation, the association constants being 3.3 mol^–1 dm³ for Na⁺ Br^– and 20–23 mol^–1 dm³ for Na(Ia–c)⁺ Br^–. The syntheses of compounds (Ic) and (Id) are described.     

Mechanisms for the Ni-mediated oxidation of benzene to phenol by N2O

The gas-phase Ni⁺-mediated benzene oxidation by N₂O on both quartet and doublet potential energy surfaces are surveyed using density functional theory (DFT). Geometries and energies for all relevant intermediates are calculated. The initial N₂O reduction for forming NiO⁺ takes place only via reaction with the excited Ni⁺(⁴F) through the N–O insertion mechanism. The second step of the oxidation can involve two mechanisms: ‘nonradical’ through benzene H migration following the formation of the boat complex of benzene–NiO⁺ or ‘oxygen-insertion’ via rearrangement to an arenium intermediate from the chair-type benzene–NiO⁺ encounter complex. Both mechanisms are energetically available.     

IR Study of ion-molecular interactions in a DMF-HCl system

The Multiple Attenuated Total Reflection (MATR) IR-spectra of HCl solutions in DMF (0–48.55% HCl) were recorded and analyzed in the range of 900–4000 cm^–1. Depending on the ratio of compounds, a variety of complexes (2 DMF) · HCl (1), DMF · HCl (2), DMF · (2 HCl) (3) are formed in the system. The concentrations of the complexes were measured. Complex2 possesses a quasi-ionic structure Me₂NHCO...H...Cl. The addition of a DMF molecule to complex2 with formation of complex1 does not result in destruction of the quasi-ionic structure of the DMF-HCl bond. In excess HCl, this structure is decomposed and the complex with the ion pair structure Me₂NHCOH⁺ (ClHCl)^– is formed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1577–1582, September, 1993.     

Antioxidant Activity of Adamantylphenols

Antioxidant properties of phenols with ortho- and para-adamantyl substituents are studied by microcalorimetry using cumene oxidation as a model reaction. The experimental rate constants for inhibition by adamantylphenols (k ₇) are comparable to the corresponding values for sterically hindered phenols, and the stoichiometric inhibition coefficient is higher than the calculated one. Adamantylphenols with adamantyl and methyl or methylene bridge groups in the ortho positions with respect to the functional group exhibit the maximal activity. The inhibition rate constant takes a maximal value of k ₇ = 3.3 × 10⁴ l mol^–1 s^–1 for 2,4-di-(adamantyl-1)-6-methylphenol and a minimal value of k ₇ = 1.4 × 10³ l mol^–1 s^–1 for 2,4,6-triadamantylphenol. The difference in the rate constants is due to steric hindrances in the reaction of a peroxy radical with the functional group of a phenol surrounded by bulky adamantyl groups.     

Ab initio investigations of the bound rovibrational levels of NeH 2 + , NeHD+, and NeD 2 +

Summary Bound rovibrational levels have been calculated for NeH ₂ ⁺ , NeHD⁺, and NeD ₂ ⁺ using three recent fits to an accurateab initio PES. The NeH ₂ ⁺ molecule behaves essentially as a linear molecule, the predicted rotational constant is 2.57 cm^–1. The fundamental frequencies are 811, 1189, and 1748 cm^–1 for the Ne-H ₂ ⁺ stretch, the Ne-H ₂ ⁺ bend and H ₂ ⁺ stretching modes, respectively.Dedicated to the 60th birthday of Prof. W. Kutzelnigg, Bochum