Stereo-dynamics study of O + HCl → OH + Cl reaction on the <Superscript>3</Superscript>A″, <Superscript>3</Superscript>A′, and <Superscript>1</Superscript>A′ states

Using three accurate potential energy surfaces of the ³A″, ³A′, and ¹A′ states constructed recently, we present a quasi-classical trajectory (QCT) calculation for O + HCl (v = 0, j = 0) → OH + Cl reaction at the collision energies (E _col) of 14.0–20.0 kcal/mol. The three angular distribution functions—P(q_r ) P(\theta_{r} ) , P(j_r ) P(\varphi_{r} ) , and P(q_r ,j_r ) P(\theta_{r} ,\varphi_{r} ) , together with the four commonly used polarization-dependent differential cross-sections, \frac2ps \fracds₀₀ dw_t , \frac2ps \fracds₂₀ dw_t , \frac2ps \fracds_{22 +} dw_t , \textand \frac2ps \fracds_{21 -} dw_t {\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{00} }}{{d\omega_{t} }}},\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{20} }}{{d\omega_{t} }}},\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{22 + } }}{{d\omega_{t} }}},\,{\text{and}}\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{21 - } }}{{d\omega_{t} }}} are exhibited to get an insight into the alignment and the orientation of the product OH radical. There is a similar behavior of the tendency scattering direction for the two triplet electronic states (³A″ and ³A′)—backward scattering dominates, however, forward scattering prevails for the case of ¹A′ state. Also, obvious differences have been found in the stereo-dynamical information, which reveals the influences of the potential energy surface and the collision energy. The degrees of polarization and the influence of the collision energy on the stereo-dynamics characters of the title reaction are both demonstrated in the order of ³A′ > ³A″ > ¹A′.     

Algorism for the solution of the exponential integral in non-isothermal kinetics at linear heating

The solution of the exponential integral at linear heating for the general case that the activation energy linearly depends on temperature according toE(T)=E ₀+RBT is

Thermochemical study on ternary complex of dysprosium <Emphasis Type="Italic">m</Emphasis>-nitrobenzoic acid with <Emphasis Type="Italic">o</Emphasis>-phenanthroline

A ternary binuclear complex of dysprosium chloride hexahydrate with m-nitrobenzoic acid and 1,10-phenanthroline, [Dy(m-NBA)₃phen]₂·4H₂O (m-NBA: m-nitrobenzoate; phen: 1,10-phenanthroline) was synthesized. The dissolution enthalpies of [2phen·H₂O(s)], [6m-HNBA(s)], [2DyCl₃·6H₂O(s)], and [Dy(m-NBA)₃phen]₂·4H₂O(s) in the calorimetric solvent (V_DMSO:V_MeOH = 3:2) were determined by the solution–reaction isoperibol calorimeter at 298.15 K to be \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2phen·H₂O(s), 298.15 K] = 21.7367 ± 0.3150 kJ·mol⁻¹, \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [6m-HNBA(s), 298.15 K] = 15.3635 ± 0.2235 kJ·mol⁻¹, \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2DyCl₃·6H₂O(s), 298.15 K] = −203.5331 ± 0.2200 kJ·mol⁻¹, and \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [[Dy(m-NBA)₃phen]₂·4H₂O(s), 298.15 K] = 53.5965 ± 0.2367 kJ·mol⁻¹, respectively. The enthalpy change of the reaction was determined to be \Updelta_\textr H_\textm^q = 3 6 9. 4 9 ±0. 5 6   \textkJ·\textmol ^{- 1} . \Updelta_{\text{r}} H_{\text{m}}^{\theta } = 3 6 9. 4 9 \pm 0. 5 6 \;{\text{kJ}}\cdot {\text{mol}}^{ - 1} . According to the above results and the relevant data in the literature, through Hess’ law, the standard molar enthalpy of formation of [Dy(m-NBA)₃phen]₂·4H₂O(s) was estimated to be \Updelta_\textf H_\textm^q \Updelta_{\text{f}} H_{\text{m}}^{\theta } [[Dy(m-NBA)₃phen]₂·4H₂O(s), 298.15 K] = −5525 ± 6 kJ·mol⁻¹.     

Ion-Solvation Behavior of Pyridinium Dichromate in Water–N,N-Dimethyl Formamide Solvent Mixtures

The electrical conductances of pyridinium dichromate have been measured in N,N-dimethyl formamide–water mixtures of different compositions in the temperature range 283–313 K. The limiting molar conductance, Λ₀, association constant of the ion pair, K _A, and dissociation constant K _C have been calculated using the Shedlovsky and Kraus–Bray equations. The effective ionic radii (r _i ) of C₅H₅NH⁺ and Cr₂O₇ ^-\mathrm{Cr}_{2}\mathrm{O}_{7}^{ -} have been determined from the L_i⁰\Lambda_{i}^{0} values using Gill’s modification of Stokes’ law. The influence of the mixed solvent composition on the solvation of ions is discussed with the help of the ‘R’-factor ( R = \frachL _±⁰(solvent)hL _±⁰(water)R = \frac{\eta \Lambda_{ \pm}^{0}(\mathrm{solvent})}{\eta\Lambda_{ \pm}^{0}(\mathrm{water})}). Thermodynamic parameters are evaluated and reported. The results of this study are interpreted in terms of ion–solvent interactions and solvent properties.     

Large Carbon Cluster Anions Generated by Laser Ablation of Graphene

The formation of large even-numbered carbon cluster anions, \textC_\textn ^- {\text{C}}_{\text{n}}^{ - } , with n up to 500 were observed in the mass spectra generated by laser ablation of graphene and graphene oxide, and the signal intensity of the latter is much weaker than that of the former. The cluster distributions generated from graphene can be readily altered by changing the laser energy and the accumulation period in the FT - ICR cell. By choosing suitable experimental conditions, weak signals of odd-numbered anions from \textC₁₂₅ ^- {\text{C}}_{{125}}^{ - } to \textC₂₁₁ ^- {\text{C}}_{{211}}^{ - } , doubly charged anions from \textC₇₀^{2 -} {\text{C}}_{{70}}^{{2 - }} to \textC₂₃₀^{2 -} {\text{C}}_{{230}}^{{2 - }} and triply charged cluster anions from \textC₈₀^{3 -} {\text{C}}_{{80}}^{{3 - }} to \textC₂₂₄^{3 -} {\text{C}}_{{224}}^{{3 - }} can be observed. Tandem MS was applied to some selected cluster anions. Though no fragment anions larger than \textC₂₀ ^- {\text{C}}_{{20}}^{ - } can be observed by the process of collisional activation with N₂ gas for most cluster ions, several cluster anions can lose units of C₂, C₄, C₆ or C₈ in their collision process. The differences in their dissociation kinetics and structures require further calculations and experimental studies.     

Dynamics of Hydration of Alkylsulfonate Anions in Aqueous Solutions

The ¹⁷O-NMR spin-lattice relaxation times (T ₁) of water molecules in aqueous solutions of n-alkylsulfonate (C₁ to C₆) and arylsulfonic anions were determined as a function of concentration at 298 K. Values of the dynamic hydration number, (S^-) = n_h ^- (t_c^- /t_c⁰ - 1)(\mathrm{S}^{-}) = n_{\mathrm{h}}^{ -} (\tau_{\mathrm{c}}^{-} /\tau_{\mathrm{c}}^{0} - 1), were determined from the concentration dependence of T ₁. The ratios (t_c ^-/t_c⁰\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0}) of the rotational correlation times (t_c ^-\tau_{\mathrm{c}}^{ -} ) of the water molecules around each sulfonate anion in the aqueous solutions to the rotational correlation time of pure water (t_c⁰\tau_{\mathrm{c}}^{0}) were obtained from the n _DHN(S⁻) and the hydration number (n_h ^-n_{\mathrm{h}}^{ -} ) results, which was calculated from the water accessible surface area (ASA) of the solute molecule. The t_c ^-/t_c⁰\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0} values for alkylsulfonate anions increase with increasing ASA in the homologous-series range of C₁ to C₄, but then become approximately constant. This result shows that the water structures of hydrophobic hydration near large size alkyl groups are less ordered. The rotational motions of water molecules around an aromatic group are faster than those around an n-alkyl group with the same ASA. That is, the number of water–water hydrogen bonds in the hydration water of aromatic groups is smaller in comparison with the hydration water of an n-alkyl group having the same ASA. Hydrophobic hydration is strongly disturbed by a sulfonate group, which acts as a water structure breaker. The disturbance effect decreases in the following order: $\mbox{--} \mathrm{SO}_{3}^{-} > \mbox{--} \mathrm{NH}_{3}^{ +} > \mathrm{OH}> \mathrm{NH}_{2}$\mbox{--} \mathrm{SO}_{3}^{-} > \mbox{--} \mathrm{NH}_{3}^{ +} > \mathrm{OH}> \mathrm{NH}_{2}. The partial molar volumes and viscosity B _V coefficients for alkylsulfonate anions are linearly dependent on their n _DHN(S⁻) values.     

Thermochemistry of 2-Aminopyridine (C<Subscript>5</Subscript>H<Subscript>6</Subscript>N<Subscript>2</Subscript>)(s)

The molar enthalpies of solution of 2-aminopyridine at various molalities were measured at T=298.15 K in double-distilled water by means of an isoperibol solution-reaction calorimeter. According to Pitzer’s theory, the molar enthalpy of solution of the title compound at infinite dilution was calculated to be D_solH_m^￥ = 14.34 kJ·mol^-1\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\infty} = 14.34~\mbox{kJ}\cdot\mbox{mol}^{-1}, and Pitzer’s ion interaction parameters b_MX^(0)L, b_MX^(1)L\beta_{\mathrm{MX}}^{(0)L}, \beta_{\mathrm{MX}}^{(1)L}, and C_MX^fLC_{\mathrm{MX}}^{\phi L} were obtained. Values of the relative apparent molar enthalpies ( ^φ L) and relative partial molar enthalpies of the compound ([`(L)]₂)\bar{L}_{2}) were derived from the experimental enthalpies of solution of the compound. The standard molar enthalpy of formation of the cation C₅H₇N₂ ⁺\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{ +} in aqueous solution was calculated to be D_fH_m^o(C₅H₇N₂⁺,aq)=-(2.096±0.801) kJ·mol^-1\Delta_{\mathrm{f}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{+},\mbox{aq})=-(2.096\pm 0.801)~\mbox{kJ}\cdot\mbox{mol}^{-1}.     

Dissolution Thermodynamics of 1,2,3-Triazole Nitrate in Water

The enthalpies of dissolution of 1,2,3-triazole nitrate in water were measured using a RD496-2000 Calvet microcalorimeter at four different temperatures under atmospheric pressure. Differential enthalpies (Δ_dif H) and molar enthalpies (Δ_diss H) of dissolution were determined. The corresponding kinetic equations that describe the dissolution rate at the four experimental temperatures are \fracdadt / s ^{- 1} = 10 ^{- 3.75}( 1 - a)^0.96\frac{d\alpha}{dt} / \mathrm{s}^{ - 1} =10^{ - 3.75}( 1 - \alpha)^{0.96} (T=298.15 K), \fracdadt /s ^{- 1} = 10 ^{- 3.73}( 1 - a)^1.00\frac{d\alpha}{dt} /\mathrm{s}^{ - 1} = 10^{ - 3.73}( 1 - \alpha)^{1.00} (T=303.15 K), \fracdadt / s ^{- 1} = 10 ^{- 3.72}( 1 - a)^0.98\frac{d\alpha}{dt} / \mathrm{s}^{ - 1} = 10^{ - 3.72}( 1 - \alpha)^{0.98} (T=308.15 K) and \fracdadt / s ^{- 1} = 10 ^{- 3.71}( 1 -a)^0.97\frac{d\alpha}{dt} / \mathrm{s}^{ - 1} = 10^{ - 3.71}( 1 -\alpha)^{0.97} (T=313.15 K). The determined values of the activation energy E and pre-exponential factor A for the dissolution process are 5.01 kJ⋅mol⁻¹ and 10^−2.87 s⁻¹, respectively.     

Densities, Specific Heat Capacities, Apparent and Partial Molar Volumes and Heat Capacities of Glycine in?Aqueous Solutions of Formamide, Acetamide, and?N,N-Dimethylacetamide at T=298.15?K and?Ambient Pressure

Apparent molar volumes (V _2,φ ) and heat capacities (C _p2,φ ) of glycine in known concentrations (1.0, 2.0, 4.0, 6.0, and 8.0 mol⋅kg⁻¹) of aqueous formamide (FM), acetamide (AM), and N,N-dimethylacetamide (DMA) solutions at T=298.15 K have been calculated from relative density and specific heat capacity measurements. These measurements were completed using a vibrating-tube flow densimeter and a Picker flow microcalorimeter, respectively. The concentration dependences of the apparent molar data have been used to calculate standard partial molar properties. The latter values have been combined with previously published standard partial molar volumes and heat capacities for glycine in water to calculate volumes and heat capacities associated with the transfer of glycine from water to the investigated aqueous amide solutions, D[`(V)]<sub>2,tr</sub><sup>o</sup>\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`(C)]_p2,tr^o\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} respectively. Calculated values for D[`(V)]<sub>2,tr</sub><sup>o</sup>\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`(C)]_p2,tr^o\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} are positive for all investigated concentrations of aqueous FM and AM solutions. However, values for D[`(C)]_p2,tr^o\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} associated with aqueous DMA solutions are found to be negative. The reported transfer properties increase with increasing co-solute (amide) concentration. This observation is discussed in terms of solute + co-solute interactions. The transfer properties have also been used to estimate interaction coefficients.     

The Estimation of Standard Molar Enthalpies of Solution for VOSO<Subscript>4</Subscript>⋅<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O(s) in Water and in Aqueous H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

The molar enthalpies of solution of VOSO₄⋅3.52H₂O(s) at various molalities in water and in aqueous sulfuric acid (0.1 mol⋅kg⁻¹), Δ_sol H _m, were measured by a solution-reaction isoperibol calorimeter at 298.15±0.01 K. An improved Archer’s method to estimate the standard molar enthalpy of solution, D_solH⁰_m\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}, was put forward. In terms of the improved method, the values of D_solH⁰_m=-24.12±0.03 kJ·mol^-1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-24.12\pm 0.03~\mbox{kJ}{\cdot}\mbox{mol}^{-1} of VOSO₄⋅3.52H₂O(s) in water and D_solH⁰_m=-15.38±0.06 kJ·mol^-1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-15.38\pm 0.06~\mbox{kJ}{\cdot}\mbox{mol}^{-1} in aqueous sulfuric acid were obtained, respectively. The data indicates that the energy state of VOSO₄ in aqueous H₂SO₄ is higher than that in pure water.     

Solubility Measurements of Crystalline NiO in Aqueous Solution as a Function of Temperature and pH

Results of solubility experiments involving crystalline nickel oxide (bunsenite) in aqueous solutions are reported as functions of temperature (0 to 350 °C) and pH at pressures slightly exceeding (with one exception) saturation vapor pressure. These experiments were carried out in either flow-through reactors or a hydrogen-electrode concentration cell for mildly acidic to near neutral pH solutions. The results were treated successfully with a thermodynamic model incorporating only the unhydrolyzed aqueous nickel species (viz., Ni²⁺) and the neutrally charged hydrolyzed species (viz., Ni(OH)₂⁰)\mathrm{Ni(OH)}_{2}^{0}). The thermodynamic quantities obtained at 25 °C and infinite dilution are, with 2σ uncertainties: log₁₀K_s0^o = (12.40 ±0.29),\varDelta_rG_m^o = -(70. 8 ±1.7)\log_{10}K_{\mathrm{s0}}^{\mathrm{o}} = (12.40 \pm 0.29),\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = -(70. 8 \pm 1.7) kJ⋅mol⁻¹; \varDelta_rH_m^o = -(105.6 ±1.3)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = -(105.6 \pm 1.3) kJ⋅mol⁻¹; \varDelta_rS_m^o = -(116.6 ±3.2)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} =-(116.6 \pm 3.2) J⋅K⁻¹⋅mol⁻¹; \varDelta_rC_p,m^o = (0 ±13)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = (0 \pm 13) J⋅K⁻¹⋅mol⁻¹; and log₁₀K_s2^o = -(8.76 ±0.15)\log_{10}K_{\mathrm{s2}}^{\mathrm{o}} = -(8.76 \pm 0.15); \varDelta_rG_m^o = (50.0 ±1.7)\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = (50.0 \pm 1.7) kJ⋅mol⁻¹; \varDelta_rH_m^o = (17.7 ±1.7)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = (17.7 \pm 1.7) kJ⋅mol⁻¹; \varDelta_rS_m^o = -(108±7)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} = -(108\pm 7) J⋅K⁻¹⋅mol⁻¹; \varDelta_rC_p,m^o = -(108 ±3)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = -(108 \pm 3) J⋅K⁻¹⋅mol⁻¹. These results are internally consistent, but the latter set differs from those gleaned from previous studies recorded in the literature. The corresponding thermodynamic quantities for the formation of Ni²⁺ and Ni(OH)₂⁰\mathrm{Ni(OH)}_{2}^{0} are also estimated. Moreover, the Ni(OH)₃ ^-\mathrm{Ni(OH)}_{3}^{ -} anion was never observed, even in relatively strong basic solutions (m_{OH ^-} = 0.1m_{\mathrm{OH}^{ -}} = 0.1 mol⋅kg⁻¹), contrary to the conclusions drawn from all but one previous study.     

Electrocatalytic oxidation of nitrite at a terpyridine manganese(II) complex modified carbon past electrode

A carbon past electrode modified with [Mn(H₂O)(N₃)(NO₃)(pyterpy)], ( \textpyterpy = 4￠- ( 4 - \textpyridyl ) - 2,2￠:\text6￠,\text2￠￠- \textterpyridine ) \left( {{\text{pyterpy}} = 4\prime - \left( {4 - {\text{pyridyl}}} \right) - 2,2\prime:{\text{6}}\prime,{\text{2}}\prime\prime - {\text{terpyridine}}} \right) complex have been applied to the electrocatalytic oxidation of nitrite which reduced the overpotential by about 120 mV with obviously increasing the current response. Relative standard deviations for nitrite determination was less than 2.0%, and nitrite can be determined in the ranges of 5.00 × 10⁻⁶ to 1.55 × 10⁻² mol L⁻¹, with a detection limit of 8 × 10⁻⁷ mol L⁻¹. The treatment of the voltammetric data showed that it is a pure diffusion-controlled reaction, which involves one electron in the rate-determining step. The rate constant k′, transfer coefficient α for the catalytic reaction, and diffusion coefficient of nitrite in the solution, D, were found to be 1.4 × 10⁻², 0.56× 10⁻⁶, and 7.99 × 10⁻⁶ cm² s⁻¹, respectively. The mechanism for the interaction of nitrite with the Mn(II) complex modified carbon past electrode is proposed. This work provides a simple and easy approach to detection of nitrite ion. The modified electrode indicated reproducible behavior, anti-fouling properties, and stability during electrochemical experiments, making it particularly suitable for the analytical purposes.     

Flow-dependent rejection of polystyrene from microporous membranes

Dilute solutions of polystyrene (molecular weight 1 × 10⁵?2 × 10⁷) in a mixed solvent of 90% carbon tetrachloride-10% methanol were filtered through track-etched porous mica membranes. The reflection coefficient σ, defined as the fraction of polymer held back by the membrane, was measured as a function of polymer size r_s, pore radius r_o, and solvent flow rate q through each pore. Polymer size was characterized by the Stokes-Einstein radius, as determined from diffusion coefficients measured by quasielastic light scattering, and chain relaxation times τ were estimated from measured intrinsic viscosities. In the case of chains whose unperturbed radius was smaller than the pore, σ depended on the ratio r_s/r_o in the manner predicted by a hard-sphere theory, as long as \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma \tau < < 1 $\end{document}, where \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} is the mean rate of strain of solvent at the pore entrance. However, when the polymer chains exceeded the pore in size, σ depended on flow rate and decreased from almost unity, at small q, toward zero at high q. The relationship between σ and q was nearly independent of polymer and pore size, consistent with a theory based on scaling concepts of how polymer chains deform at the entrance of a pore, but the reduction in σ as q increased was very gradual and did not exhibit the sharp transition predicted by the theory. We were able to empirically correlate all the data for σ when r_s > r_o by a single similarity variable \documentclass{article}\pagestyle{empty}\begin{document}$ \theta = {{({{r_s} \mathord{\left/ {\vphantom {{r_s} {r_0}}} \right. \kern-\nulldelimiterspace} {r_0}})} \mathord{\left/ {\vphantom {{({{r_s} \mathord{\left/ {\vphantom {{r_s} {r_0}}} \right. \kern-\nulldelimiterspace} {r_0}})} {(\dot \gamma \tau)^n}}} \right. \kern-\nulldelimiterspace} {(\dot \gamma \tau)^n}} \sim ({{r_s} \mathord{\left/ {\vphantom {{r_s} {r_0}}} \right. \kern-\nulldelimiterspace} {r_0}})^{1 - 3n} q^{- n} $\end{document}; a least-squares fit gave n = 0.33, showing that σ is insensitive to polymer size for large chains.     

Kinetic parameters for thermal decomposition of microcrystalline,vegetal, and bacterial cellulose

Cellulose can be obtained from innumerable sources such as cotton, trees, sugar cane bagasse, wood, bacteria, and others. The bacterial cellulose (BC) produced by the Gram-negative acetic-acid bacterium Acetobacter xylinum has several unique properties. This BC is produced as highly hydrated membranes free of lignin and hemicelluloses and has a higher molecular weight and higher crystallinity. Here, the thermal behavior of BC, was compared with those of microcrystalline (MMC) and vegetal cellulose (VC). The kinetic parameters for the thermal decomposition step of the celluloses were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and at heating rates of 5, 10, and 20 °C/min, the E _α and B _α terms could be determined and consequently the pre-exponential factor A _α as well as the kinetic model g(α). The pyrolysis of celluloses followed kinetic model g(a) = [ - ln(1 - a)]^{1 \mathord}

Studies on electron transfer reactions: reduction of heteropoly 10-tungstodivanadophosphate by <Emphasis Type="SmallCaps">l</Emphasis>-cysteine in aqueous acid medium

l-cysteine undergoes facile electron transfer with heteropoly 10-tungstodivanadophosphate, [ \textPV^\textV \textV^\textV \textW _{1 0} \textO _{4 0} ]^{5 -} , \left[ {{\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} } \right]^{5 - } , at ambient temperature in aqueous acid medium. The stoichiometric ratio of [cysteine]/[oxidant] is 2.0. The products of the reaction are cystine and two electron-reduced heteropoly blue, [PV^IVV^IVW₁₀O₄₀]⁷⁻. The rates of the electron transfer reaction were measured spectrophotometrically in acetate–acetic acid buffers at 25 °C. The orders of the reaction with respect to both [cysteine] and [oxidant] are unity, and the reaction exhibits simple second-order kinetics at constant pH. The pH-rate profile indicates the participation of deprotonated cysteine in the reaction. The reaction proceeds through an outer-sphere mechanism. For the dianion ⁻SCH₂CH(NH₃ ⁺)COO⁻, the rate constant for the cross electron transfer reaction is 96 M⁻¹s⁻¹ at 25 °C. The self-exchange rate constant for the ^- \textSCH₂ \textCH( \textNH₃ ⁺ )\textCOO ^- \mathord

Specific adsorption of bromide and iodide ions from N-methyl formamide solutions with constant ionic strength on liquid ga electrode

The differential capacitance curves were measured with an ac bridge in the Ga/[N-MF + 0.1 m M KBr + 0.1 (1 − m) M KClO₄] and Ga/[N-MF + 0.1 m M KI + 0.1 (1 − m) M KClO₄] systems at the following fractions m of surface-active anions: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1. As compared with other solvents, N-methyl formamide (N-MF) enables one to realize the largest positive charges of Ga electrode, at which it remains ideally polarizable (up to 20 μ/cm²). The data on the specific adsorption of Br⁻ and I⁻ anions in the system can be quantitatively described by the Frumkin’s isotherm; to the first approximation, free energy of halide ion (Hal⁻) adsorption DG_{adsHal ^{- 1}} \Delta G_{adsHal^{ - 1} } is a linear function of electrode charge. It is found that, in contrast to the Hg/N-MF interface, DG_{adsHal ^{- 1}} \Delta G_{adsHal^{ - 1} } at the Ga/N-MF interface varies in the reverse order: Br^t— ∼ I⁻ < Cl⁻. From the measured results, we can conclude that the energy of metal-Hal⁻ interaction increases in series: $\Delta G_{M - Cl^ - } > \Delta G_{M - Br^ - } > \Delta G_{M - I^ - } $\Delta G_{M - Cl^ - } > \Delta G_{M - Br^ - } > \Delta G_{M - I^ - } and the difference (DG_{Ga - Hal1^-} - DG_{Ga - Hal2^-} )(\Delta G_{Ga - Hal_1^ - } - \Delta G_{Ga - Hal_2^ - } ) is larger than the difference between the solvation energies of Hal^- (DG_{S - Hal1^-} - DG_{S - Hal2^-} )Hal^ - (\Delta G_{S - Hal_1^ - } - \Delta G_{S - Hal_2^ - } ).     

Calculating activation energy of amorphous phase with the Lambert W function

A new approach for determining the activation energy of amorphous alloys is developed. Setting the second order differential coefficient of heterogeneous reaction rate equation of non-isothermal heating as zero at extreme points of DSC curve, we obtain the new correlation taking form:

Dissolution properties of hexanitrohexaazaisowurtzitane (CL-20) in ethyl acetate and acetone

The enthalpies of dissolution in ethyl acetate and acetone of hexanitrohexaazaisowurtzitane (CL-20) were measured by means of a RD496-2000 Calvet microcalorimeter at 298.15 K, respectively. Empirical formulae for the calculation of the enthalpy of dissolution (Δ_diss H), relative partial molar enthalpy (Δ_diss H _partial), relative apparent molar enthalpy (Δ_diss H _apparent), and the enthalpy of dilution (Δ_dil H _1,2) of each process were obtained from the experimental data of the enthalpy of dissolution of CL-20. The corresponding kinetic equations describing the two dissolution processes were \frac\textda\textdt = 1.60 ×10 ^{- 2} (1 - a)^0.84 {\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = 1.60 \times 10^{ - 2} (1 - \alpha )^{0.84} for dissolution process of CL-20 in ethyl acetate, and \frac\textda\textdt = 2.15 ×10 ^{- 2} (1 - a)^0.89 {\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = 2.15 \times 10^{ - 2} (1 - \alpha )^{0.89} for dissolution process of CL-20 in acetone.     

Heat capacity and thermodynamic properties of tellurites Yb2(TeO3)3, Dy2(TeO3)3 and Er2(TeO3)3

The experimental results obtained for the specific molar heat capacity of the tellurites Yb₂(TeO₃)₃, Dy₂(TeO₃)₃ and Er₂(TeO₃)₃ are processed by the least squares method. The temperature dependence of the specific molar heat capacity derived is used to determine the thermodynamic properties: entropy ( \Updelta_T￠^T S_m⁰ ), \left( {\Updelta_{T\prime }^{T} S_{m}^{0} } \right), enthalpy ( \Updelta_T￠^T H_m⁰ ) \left( {\Updelta_{T\prime }^{T} H_{m}^{0} } \right) and Gibbs function ( \Updelta_T￠^T G_m⁰ ) \left( {\Updelta_{T\prime }^{T} G_{m}^{0} } \right) of the tellurites Yb₂(TeO₃)₃, Dy₂(TeO₃)₃ and Er₂(TeO₃)₃.     

Thermal decomposition kinetics of magnesite from thermogravimetric data

Thermal decomposition kinetics of magnesite were investigated using non-isothermal TG-DSC technique at heating rate (β) of 15, 20, 25, 35, and 40 K min⁻¹. The method combined Friedman equation and Kissinger equation was applied to calculate the E and lgA values. A new multiple rate iso-temperature method was used to determine the magnesite thermal decomposition mechanism function, based on the assumption of a series of mechanism functions. The mechanism corresponding to this value of F(a), which with high correlation coefficient (r-squared value) of linear regression analysis and the slope was equal to −1.000, was selected. And the Malek method was also used to further study the magnesite decomposition kinetics. The research results showed that the decomposition of magnesite was controlled by three-dimension diffusion; mechanism function was the anti-Jander equation, the apparent activation energy (E), and the pre-exponential term (A) were 156.12 kJ mol⁻¹ and 10^5.61 s⁻¹, respectively. The kinetic equation was