The Unusual Spectrum of the Mixture of Tin-octabutoxy Naphthalocyanine and SnCl2 in CH2Cl2

The Q-band position of tin-centered 5, 9, 14, 18, 23, 27, 32, 36-octabutoxy 2, 3-phthalocyanine(SnNc(OBu)8) exhibits dramatic red-shift as mixed with SnCl2 in CH2Cl2.     

Peculiarities of Si and SiO2 Etching Kinetics in HBr + Cl2 + O2 Inductively Coupled Plasma

Plasma Chemistry and Plasma Processing - Peculiarities of the etching kinetics and mechanisms for Si and SiO2 in the HBr?+?Cl2?+?O2 inductively coupled plasma were...     

Quasi-classical trajectory study of the dynamics of the Cl + CH4→ HCl + CH3 reaction

We present an on-the-fly classical trajectory study of the Cl + CH(4)→ HCl + CH(3) reaction using a specific reaction parameter (SRP) AM1 Hamiltonian that was previously optimized for the Cl + ethane reaction [S. J. Greaves et al., J. Phys Chem A, 2008, 112, 9387]. The SRP-AM1 Hamiltonian is shown to be a good model for the potential energy surface of the title reaction. Calculated differential cross sections, obtained from trajectories propagated with the SRP-AM1 Hamiltonian compare favourably with experimental results for this system. Analysis of the vibrational modes of the methyl radical shows different scattering distributions for ground and vibrationally excited products.     

The electrochemical behaviour of polycrystalline silver electrodes in Na2CO3 solution and the effect of ClO− 4 ions

The electrochemical behaviour of polycrystalline silver electrodes in Na₂CO₃ solutions was studied under potentiodynamic and potentiostatic conditions and complemented with X-ray diffraction analysis. Potentiodynamic E/i anodic curves exhibit active passive transition prior to an oxygen evolution reaction. The active region involves a small peak AI followed by a major peak AII before the passive region. Peak AI is assigned to the formation of an Ag₂O layer while peak AII is due to the formation of an Ag₂CO₃ layer. The height of the anodic peaks increases with increasing Na₂CO₃ concentration, scan rate and temperature. The effect of increasing additions of NaClO₄ on the electrochemical behaviour of Ag in Na₂CO₃ solutions was investigated. The perchlorate ions stimulate the active dissolution of Ag, presumably as a result of the formation of soluble AgClO₄ salt. In the passive region, ClO⁻ ₄ ions tend to break down the dual passive film, leading to pitting corrosion at a certain critical pitting potential. The pitting potential decreases with ClO⁻ ₄ concentration. Potentiostatic current/time transients showed that the formation of Ag₂O and Ag₂CO₃ layers involves a nucleation and growth mechanism under diffusion control. However, in the presence of ClO⁻ ₄ ions, the incubation time for pit initiation decreases on increasing the anodic potential step. Received: 3 July 1998 / Accepted: 10 March 1999     

Unimolecular reactions in the CF3CH2Cl ↔ CF2ClCH2F system: isomerization by interchange of Cl and F atoms

The recombination of CF(2)Cl and CH(2)F radicals was used to prepare CF(2)ClCH(2)F* molecules with 93 ± 2 kcal mol(-1) of vibrational energy in a room temperature bath gas. The observed unimolecular reactions in order of relative importance were: (1) 1,2-ClH elimination to give CF(2)═CHF, (2) isomerization to CF(3)CH(2)Cl by the interchange of F and Cl atoms and (3) 1,2-FH elimination to give E- and Z-CFCl═CHF. Since the isomerization reaction is 12 kcal mol(-1) exothermic, the CF(3)CH(2)Cl* molecules have 105 kcal mol(-1) of internal energy and they can eliminate HF to give CF(2)═CHCl, decompose by rupture of the C-Cl bond, or isomerize back to CF(2)ClCH(2)F. These data, which provide experimental rate constants, are combined with previously published results for chemically activated CF(3)CH(2)Cl* formed by the recombination of CF(3) and CH(2)Cl radicals to provide a comprehensive view of the CF(3)CH(2)Cl* ? CF(2)ClCH(2)F* unimolecular reaction system. The experimental rate constants are matched to calculated statistical rate constants to assign threshold energies for the observed reactions. The models for the molecules and transition states needed for the rate constant calculations were obtained from electronic structures calculated from density functional theory. The previously proposed explanation for the formation of CF(2)═CHF in thermal and infrared multiphoton excitation studies of CF(3)CH(2)Cl, which was 2,2-HCl elimination from CF(3)CH(2)Cl followed by migration of the F atom in CF(3)CH, should be replaced by the Cl/F interchange reaction followed by a conventional 1,2-ClH elimination from CF(2)ClCH(2)F. The unimolecular reactions are augmented by free-radical chemistry initiated by reactions of Cl and F atoms in the thermal decomposition of CF(3)CH(2)Cl and CF(2)ClCH(2)F.     

EIS analysis of electrode kinetics for La2NiO4 + δ cathode in contact with Ce0.8Sm0.2O1.9 electrolyte: from DRT analysis to physical model of the electrochemical process

Journal of Solid State Electrochemistry - The oxygen reduction kinetics on an La2NiO4 + δ electrode for electrodes of different thicknesses was investigated by means of...     

Dual chamber YSZ-based sensor for simultaneous measurement of methane and water vapor concentrations in CH4 + H2O + N2 gas mixtures

Journal of Solid State Electrochemistry - A dual chamber solid-oxide sensor for simultaneous measurement of methane and water vapor concentrations in CH4 + H2O + N2 gas...     

Increases in reaction rates and improvement of current–potential characteristics in the electrochemical oxidation of formic acid

In current-control experiments, perturbing an aqueous solution containing 0.10 M formic acid and 0.50 M HClO₄ by including a small amount of HBF₄ causes more than a 60% increase in the value of the applied current for which low-valued stationary potentials remain stable. The current increases by more than 50% at relevant potential values in potential-control experiments. Current–potential characteristics inferior to those of the HCOOH + HClO₄ solution are obtained with other solutions made by adding small amounts of a strong acid or salt. Properties that exist among the anions present in the latter solutions are possessed by BF₄⁻. Nonlinear behavior exhibited by formic acid oxidation is changed drastically by the presence of a small amount of any one of the anions studied. These results and other arguments support the hypothesis that HBF₄ enhances current–potential characteristics by causing the formation of surface anion complexes possessing OH components at low potentials.     

Solid–Liquid Stable Equilibrium of the Quaternary System LiCl + NaCl + Li2SO4 + Na2SO4 + H2O at 288.15 K

Journal of Solution Chemistry - In this study, the isothermal saturation method was applied to obtain the data for solid–liquid equilibria in a system consisting of four solids...     

The Oxidative Mechanism in Electrophilic C?H Activation: The Case of CH2F2 and CH2Cl2

The H^.‐atom transfer (HAT) reaction is investigated in the gas phase, starting from two different entrance channels, O₂^.+/CH₂X₂ and CH₂X₂^.+/O₂ (X=F, Cl), that correspond to a step of hydride transfer and to HAT, respectively. Analysis of the spin and charge along the reaction pathway shows that HAT occurs through the same reacting configuration, irrespective of whether the reactants are formed within the complex or are free isolated species.     

Chlorination of charged buckyballs: reactions of C60x+ cations (x = 1–3) with Cl2, CCl4, CDCl3, CH2Cl2, and CH3Cl

The chlorination of singly and multiply charged C₆₀ cations has been investigated with the selected-ion flow tube technique. Observations are reported for the reactions of C₆₀^·+, C₆₀²⁺ and C₆₀^·3+ with Cl₂, CCl₄, CDCl₃, CH₂Cl₂ and CH₃Cl at room temperature (295 ± 2 K) in helium at a total pressure of 0.35 ± 0.02 Torr. C₆₀^·+ and C₆₀²⁺ were observed not to chlorinate, or react in any other way, with these five molecules. Chlorine also did not react with C₆₀^·3+, but bimolecular chloride transfer and electron transfer reactions, reactions that result in charge reduction/charge separation, were observed to occur with CCl₄, CDCl₃, CH₂Cl₂ and CH₃Cl. Chloride transfer was the predominant channel seen with CCl₄, CDCl₃ and CH₂Cl₂ while electron transfer dominates the reaction with CH₃Cl. These results are consistent with trends in chloride affinity and ionization energy. The reluctant chlorination of the first two charge states of C₆₀ is attributed to the energy required to distort the carbon cage upon bond formation, while the observed chloride transfer to C₆₀^·3+ is attributed to the greater electrostatic interactions with this ion.     

Kinetic isotope effects in oxidation reaction of C2H4 and C2D4 by p-benzoquinone in the Pd2+—HClO4—CH3CN—H2O system

Russian Chemical Bulletin - Kinetic isotope effects (KIE) have been measured for oxidation reactions of ethylene by p-benzoquinone in Pd2+—MeCN—H2O—HClO4 system. Under the...     

Kinetics of H2S destruction in the radiolysis of CH4−H2S gas mixtures

The kinetics of H₂S destruction in the radiolysis of CH₄–H₂S and CH₄–H₂S–O₂ mixtures has been studied. It has been shown that G(–H₂S) depends on amounts of hydrogen sulfide and the presence of oxygen in the starting mixture and is within the range of 5–13 mol/100 eV. G(H₂) decreases with the increases of O₂ content and amounts to the constant value of 2.     

Determination of the Activity Coefficients of NaCl in the System NaCl–NH4Cl–H2O

Using ion-selective electrode(s) (ISE) the activity coefficients of NaCl in the system NaCl–NH₄Cl–H₂O at 10, 25, and 40°C were measured by a computer-controlled automatic titration system. The ionic strength fractions of NH₄Cl were 0.2, 0.4, 0.6, and 0.8, respectively. It was found that the influence of the NH₄⁺ cation on the Na glass ISE was small enough to be neglected up to 3.0 mol-kg^-1. The Pitzer equation was adopted to calculate the activity coefficients of NaCl in this system and compared with the experimental data. Comparison of results indicates that the Pitzer parameters correlated from solubility data are suitable for calculating the activity coefficients for this system within the saturated solutions.     

Pulse radiolysis study of energy transfer processes in Xe–M mixtures (M=CH2F2,CHF3,CHF2Cl,CHFCl2 and CF3Cl)

The time-resolved spectroscopy measurements were used to study the kinetics of energy transfer process in the pulse radiolysis of xenon- fluoro- and chlorofluoromethanes mixtures. The main channel, at xenon pressure above 40 Torr, seems to be of third order, while at lower xenon pressures the second order process was the main one.     

Anodic electropolymerization of tetrakis(2-thienyl)borate: is the boron retained in the polythiophene film?

The voltammetric study of potassium tetrakis(2-thienyl)borate 1 in CH₃CN showed two irreversible two-electron steps. Similarly to its tetraphenylborate analogue, the proposed mechanism involved the decomposition of 1 followed by an electropolymerization reaction. The nature of the electrogenerated polymer was different depending on the used experimental conditions. A poly(bithiophene) film was produced over the time-scale of cyclic voltammetry whereas controlled-potential electrolysis yielded a mixture of poly(bithiophene) and a boron-containing polymer, such as poly(dithienylboronous acid).     

Determination of the equilibrium constants and UV-absorption spectra for Cu2+Cl− complexes in 1 M HClO4

The complex constants for the Cu(II)-chloride complexes CuCl⁺ and CuCl₂ have been determined spectrophotometrically at 25°C and in 1 M HClO₄. The evaluation procedure employed was a regression analysis for the simultaneous determination of complex constants and absorption spectra and yielded K₁ = 2.3 ± 0.4 and K₂ = 0.72 ± 0.09. There is a strong overlap between the 2 absorption spectra (λ_max = 250 nm in both cases, ϵ₁=530, , ϵ₂ = 1620) which made it particularly necessary to arrange the numerical analysis in such a way that the spectral differences were fully exploited.     

CAS SCF ECP calculations on the optical spectrum of Mo2(O2CH)4 and on the barrier to internal rotation in Mo2Cl84−

The optical spectrum in the near UV region has been calculated for Mo₂(O₂CH)₄ using the CAS SCF method and effective core potential techniques. Assignments for the observed transitions between 20000 and 45000 cm⁻¹ are suggested. The barrier to internal rotation has been calculated for Mo₂Cl₈⁴⁻ and it is concluded that if there is a barrier at all it is very low, a result following a twist of the complex. The theoretical spectra for Mo₂(O₂CH)₄ and Mo₂Cl₈⁴⁻ are compared and discussed. It is suggested that there should exist a weak structure in the electronic spectrum of Mo₂(O₂CH)₄ in the vicinity of 10000 cm⁻¹.