Electrochemical reactions with protonations at equilibrium: Part VI. The homogeneous electron exchange reaction between a monoelectronic and A 1 e, 1 H+ system

The rate of homogeneous electron exchange between a 1 e redox couple and a 1 e, 1 H⁺ redox system is studied theoretically when the protonations are much faster than the electron exchange reactions, i.e. when they can be assumed to be at equilibrium. It is shown that the whole system is equivalent to a reaction between two simple 1 e couples, with apparent rate constants for the electron exchange. Variations of these constants are complex functions of the difference of the standard potentials of the monoelectronic system and those of the 1 e, 1 H⁺ system. They also vary with pH in a less complicated way. The reaction path and the reaction sequence (order of addition or loss of electrons and protons) are studied. A potential-pH diagram, which allows the results to be visualized, is given. It is shown that it is not possible to accelerate at the same time the reduction and oxidation of the members of the square scheme by the same monoelectronic system. Applications to redox polymer electrodes are discussed.     

Electrochemical reactions with protonations at equilibrium: Part X. The kinetics of the p-benzoquinone/hydroquinone couple on a platinum electrode

The kinetics of the p-benzoquinone/hydroquinone Q/QH₂ couple on a platinum electrode are analysed on the basis of the theory presented earlier (E. Laviron, J. Electroanal. Chem., 146 (1983) 15) for the nine-member square scheme when the protonations are assumed to be at equilibrium, using experimental data from the literature. The square scheme is of the NN type. The Tafel plots and the variations of the experimental apparent rate constants between pH 0 and 7 are in good agreement with the theoretical predictions. The heterogeneous rate constants found for the elemental electrochemical steps are as follow: Q Q^?, k_h3=1/6×10^?3 cm s^?1; QH^.QH^?, k_h5=0.11 cm s^?1; QH⁺QH^., k_h2?160 cm s^?1; k_h4 for the reaction QH₂^+.QH₂ is in the range 0.5–4 cm s^?1. Between pH 0 and 7, the reaction sequence during the reduction is, for the most part, successively H⁺e^?H⁺e^?, e^?H⁺H⁺e^?, and e^?H⁺e^?H⁺ (reverse sequence during the oxidation).     

Energy surface calculations for the reaction HF + H+ ⇌ HFH+

Various GTO basis sets were investigated for their effectiveness in determining the SCF energy and geometry of the HFH⁺ molecule. A double zeta set augmented with a p_z function on each H atom was used to calculate the potential energy surface for the collinear protonation of HF. Limited configuration interaction calculations gave an energy of ?100.27365 E_a for an HF separation of 1.819 a₀ and a bond angle of 118.1°, and an energy of protonation of 119.5 kcal/mol.     

Die Reaktion von Arsenazo III mit H+, La3+, Sm3+, Gd3+, Dy3+ und Yb3+

Ohne Zusammenfassung     

A comparative study of H+ and Li+ interactions with oxygen bases

Ab initio SCF calculations have been performed to investigate the structural and electronic features of the interactions of H⁺ and Li⁺ with the oxygen bases H₂CO and OH^?. The data indicate that the OH interactions are primarily covalent while the LiO interactions are primarily electrostatic, although the LiO interaction in LiOH has considerable covalent character.     

Spektralphotometrische Studie der Reaktionen von Methylnaphtholorange mit H+, Ti4+, Sm3+ und UO22+

Zusammenfassung Es wurde eine neue metallochrome Substanz, das 2-Bis(carboxymethyl)-aminomethyl-4(p-sulfophenyl)azo-naphthol synthetisiert, Methylnaphtholorange genannt. Ihre konsekutiven Dissoziationskonstanten wurden bestimmt, optimale Bedingungen ihrer Reaktion mit Ti⁴⁺, Sm³⁺ und UO ₂ ²⁺ aufgefunden, die Zusammensetzung der entstehenden Metallkomplexe festgestellt und die Bildungs- als auch Stabilitätskonstanten berechnet.

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Summary A new metallochromic compound, 2-Bis(carboxymethyl)-aminomethyl-4(p-sulphophenyl)-azonaphthol, (named methylnaphthol orange) has been synthezised. Its consecutive dissociation constants have been determined, optimal conditions of its reactions with Ti⁴⁺, Sm³⁺ and UO ₂ ²⁺ worked out, the composition of the metal complexes identified and the constants of formation and stability have been computed.

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Für technische Hilfe hei dieser Arbeit bin ich Herrn K. Haas dankbar.     

Complexing ability of pesticides and related compounds. Formation and stability in aqueous solution of H+ , Li+, Na+, K+, Mg2+ and Ca2+ phenoxyacetate complexes at different temperatures and ionic strengths

The formation constants of Li⁺, N⁺, K⁺, Mg²⁺ and Ca²⁺ phenoxyacetate complexes were determined potentiometrically using an (H⁺)-glass electrode at 10, 25, 37 and 45°C, at several ionic strengths, in the range 0.04?I? 0.9 mol 1^?1. Simple empirical equations for the dependence of the formation constants on ionic strength were derived. From the temperature coefficients, estimates of ΔH^o and ΔS^o were obtained.     

Energy disposal in thermal-energy charge-transfer reactions: Ar+,Kr+ and Xe+ with NH3

Thermal-energy charge-transfer reactions from the ²P_3/2 state of Ar⁺, Kr⁺ and Xe⁺ with NH₃ are shown to be non-energy resonant: the kinetic energy released in each case has been measured, and the internal energy of the NH⁺₃ product ions deduced. Possible quenching of ²P_1/2 state of rare-gas ions in ICR cells is discussed.     

H+-Cu2+ ion exchange on a Cu0-KU-23 sulfocation exchanger nanocomposite in solutions with various pH values

The influence of solution pH on H⁺-Cu²⁺ exchange equilibrium was studied for the disperse copper- KU-23 (15/100 S) macroporous strongly acid sulfocation exchanger nanocomposite. In dilute solutions of copper(II) sulfate in weakly acid media (pH 3–6), ion exchange limitation is related to the consumption of hydrogen counterions and the formation of copper counterions in a side reaction between copper particles and impurity oxygen. The concentration of hydrogen counterions in the nanocomposite is replenished as pH decreases because of their sorption from solution together with copper ions. Original Russian Text ? E.V. Zolotukhina, T.A. Kravchenko, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 5, pp. 934–938.     

Solvent effect on electron transfer reactions: Comparison of homogeneous and heterogeneous electron exchange between V3+ and V2+ in water +t-butanol mixtures

The kinetics of homogeneous and heterogeneous electron exchange V³⁺/V²⁺ was investigated in 1 M HClO₄, water +t-butanol, mixed solvent solutions (x_t-but. varied from 0 to 0.65). Non-monotonic heterogeneous and monotonic homogeneous variations of the rate constants were observed. The solvent effect on the work of bringing the reactants from infinite separation to the reaction site was estimated with the Gouy-Chapman and Debye-Hückel approximations respectively. The homogeneous kinetics data were next used to calculate the reorganization energy in the heterogeneous reaction, λ_het. Finally the influence of the solvent composition on the rate of the electrode reaction was separated into surface and bulk effects.     

K~+、Na~+、Ca~(2+)、Mg~(2+)对胜利褐煤平衡复吸水的影响

以胜利褐煤为研究对象,利用FT-IR等手段,用灰分、不同湿度下的平衡复吸水含量等,系统研究了不同相对湿度下K+、Na+、Ca2+、Mg2+的水合作用对胜利褐煤平衡复吸水含量的影响。结果表明,相同浓度不同类型的金属离子与煤样的交换能力的趋势为Ca2+Na+K+Mg2+。金属离子对胜利褐煤平衡复吸水含量影响力的顺序为Mg2+Ca2+Na+≈K+。相对湿度高时,平衡复吸水含量的主要控制因素为游离水分子之间的分子作用力;相对湿度中等时,平衡复吸水含量的主要控制因素为金属水簇与毛细管之间的毛细管作用力;相对湿度低时,平衡复吸水含量的主要控制因素为金属离子的水合作用。     

检测氢离子的荧光探针：含稠合外环的硼-二吡咯亚甲基染料的合成、光谱和电化学性质研究

本文合成了3个新型中位分别为N,N-二甲基苯胺、对-甲氧基苯基或苯基取代的含稠合外环的硼-二吡咯亚甲基染料。研究了它们的吸收光谱、稳态荧光光谱和电化学性质;采用荧光光谱滴定方法研究了它们在强极性溶剂中对氢离子的响应;将氢离子滴加到N,N-二甲基苯胺取代的硼-二吡咯亚甲基染料(1)的CH3CN-H2O(1∶1,V/V)溶液中,其溶液的荧光显著增强;染料1在可见光激发下,可以作为酸性pH范围内检测氢离子的荧光探针。     

The formation of proton and alkali-metal complexes with ligands of biological interest in aqueous solution. Thermodynamics of H+, Na+ and K+—oxalate complexes

The protonation constants of oxalic acid were determined potentiometrically at 37°C in different media—NaNo₃, KNO₃ and Et₄NI, 0.03? I ? 0.3. From these data it was possible to determine the formation of the complexes [Na(ox)]^? and [K(ox)]^? and [K(ox)]^?, and to calculate their stability constants. Simultaneous analysis of potentionmetric and calorimetric data (this work and literature) enabled the temperature and ionic strength dependendence of the equilibrium parameters to be obtained for the protonation of oxalate. Recalculation of some literature data gave the ΔH value for the formation of the [Na(ox)]^? complex. The thermodynamic parameters obtained allowed us to confirm the hypothesis that dicarboxylate anions chelate with alkali-metal ions and that these complexes are mainly entropically stabilized.     

Ab initio MO calculations on the stable conformations and their binding energies of the ion-molecule complexes: Ion = H+, Li+, Na+, K+ Be2+, and molecule = CO and N2

The most stable conformation of ion-molecule complexes involving a CO molecule were surveyed by the use of Hartree-Fock (HF) MO and third-order Moller-Plesset perturbation (MP3) methods with a 6–31G* basis set ion = H⁺, Li⁺, Na⁺, K⁺, Bc²⁺, Mg²⁺, and Ca²⁺. The MP3 level of theory reveals the ion-CO conformation in which the ion bonds to a carbon atom of CO to be the most stable; these MP3 results are contrary to the HF ones. Binding energies of ion-molecule complexes involving CO and N₂ were computed; MP3 energies are in good agreement with the experimental ones. The computed binding energies of cation-N₂ are about one-third of cation-NH₃ due to the absence of dipole moment and the smaller polarizability of N₂. The decrease in binding energy in cation-CO and -N₂ complexes, with increasing cation size, is mainly caused by the decrease of the electrostatic and polarization stabilizations.     

ESR spectra and magnetic constants of α-Al2O3:Co2+,H+ and α-Al2O3 :Co2+,X+

New anisotropic ESR spectra of Co²⁺ doped sapphire, different from hitherto known, are reported. The new spectra which are observed, beside the well-known spectra of α-Al₂O₃:Co²⁺, are shown to form two sets, each one consisting of six spectra (1–6) and (7–12). The spectra of both sets are proven to be interrelated by B_3a symmetry. g and A tensors for each set will be given. Evidence is given that the two sets are to be assigned to the defects α-Al₂O₃:Co²⁺,H⁺ and α-Al₂O₃:Co²⁺,X⁺. The former is concluded to consists of a Co²⁺ ion at the substitutional site (c) and a proton located in a potential minimum along a straight line between O^2- ions situated in O²⁺ triangles above and below the CO²⁺ ion. The potential function for the proton has been calculated by quantum-chemical calculations to clucidate the geometrical structure of the paramagnetic center. The α-Al₂O₃:Co²⁺,X⁺ could not be fully analyzed but some evidence is presented, that X⁺ might be alkali ions.     

b1Σ+ Emissions from group V–VII diatomic molecules. b 0+ → X1 0+, X2 1 emissions of AsI and SbI

Chemiluminescence from the b 0⁺ → X₁ 0⁺ band system of AsI and of the b 0⁺ → X₁ 0⁺, X₂ 1 systems of SbI in the near-infrared spectral region has been observed in a discharge flow system. Analysis of the spectra led to the spectroscopic constants (in cm^?1) of AsI: ω_e(X₁, X₂) = 257 ± 2, ω_ex_e(X₁, X₂) = 0.82 ± 0.2, T_e(b 0⁺) = 11738 ± 5, ω_e(b 0⁺) = 271 ± 2, ω_ex_e(b 0⁺) = 0.66 ± 0.2, and of SbI: T_e(X₂ 1) = 965 ± 10, ω_e(X₁, X₂) = 206 ± 6, T_e(b 0⁺) = 12328 ± 10, ω_e(b 0⁺) = 211 ± 6. The intensity ratio of the two sub-systems b 0⁺ → X₂ 1 and b 0⁺→ X₁ 0⁺ was found to be ≈0.013 in the case of SbI and ? 0.01 for AsI.     

Improvement of polarized double-zeta basis sets for molecular interactions. Complexes of NH3, OH2, and FH with H+ and Li+

Interaction energies of a proton and lithium cation with NH₃, OH₂, and HF axe computed at the SCF and Møller-Plesset levels. It is found that the basis set superposition errors at all levels with the 6-3 1G** basis set may be greatly reduced by including an additional diffuse sp shell on first-row atoms; the exponent of this shell has been optimized to 0.1.     

Proton—molecule collisional interactions. I. The H+CO(1Σ) potential energy surface

Ab initio calculations are reported for the ground state potential energy surface (PES) of a CO molecule interacting with a proton, by treating the target as a rigid rotor and by performing accurate SCF computations over a wide range of relative distances and internal angles. The special nature of the forces at play in the short-range and intermediate range regions is discussed and protonated equilibrium geometries examined. An analytic fit of the various coefficients appearing in the well known multipolar expansion of the PES is also presented and the highly anisotropic form of this interaction is discussed. Vibrational effects are finally investigated by calculations at various r_CO values and their behaviour analysed in terms of simple stretching parameters.     

Quantum mechanical scattering calculations on a spline-fitted ab initio surface: the He + H+2 (ν = 0, 1, 2) → HeH+ + H reaction

All-channel time-dependent quantum mechanical reaction probabilities are reported for the collinear He + H⁺₂(ν = 0, 1, 2) → HeH⁺ + H reaction at a total energy of 1.2 eV on previously reported diatomics-in-molecule (DIM) and spline fitted ab initio (SAI) surfaces. These results are in agreement with the previous quasiclassical trajectory results in that there is vibrational enhancement of the reaction probability on the SAI surface but not on the DIM surface. This agreement lends support to our previously drawn conclusion that small differences in the potential-energy surface can lead to substantially different dynamic results.