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}.     

Absorption Spectrophotometric,NMR and Quantum Chemical Investigations of Ground State Non-Covalent Interactions between Fullerenes and a Designed Trihomocalix[6]arene in Solution

Ground state non-covalent interactions between a newly designed macrocyclic 1,3,5-trihomo calix[6]arene receptor, designated as 1, and the C₆₀ and C₇₀ fullerenes have been studied in toluene solutions. It was observed that the absorbances of both C₆₀ and C₇₀ solutions increased upon the addition of increasing concentrations of compound 1. Job’s method of continuous variation established 1:1 stoichiometry for these fullerene-1 complexes. The binding constant (K) data reveal that compound 1 binds to C₇₀ more strongly compared to C₆₀, i.e., K_C60-1 = 230 dm³·mol^-1K_{C60\mbox{-}\boldsymbol{1}} = 230~\mathrm{dm}^{3}{\cdot}\mathrm{mol}^{-1} and K_C70-1 = 517 dm³·mol^-1K_{C70\mbox{-}\boldsymbol{1}}= 517~\mathrm{dm}^{3}{\cdot}\mathrm{mol}^{-1}. Proton NMR analysis provides very good support for strong binding between C₇₀ and 1. Estimations of the solvent reorganization energy (R _S ) suggest that the C₇₀-1 complex is stabilized more than the corresponding C₆₀-1 complex, with R_S(C60-1) = -1.970 eVR_{S(C60\mbox{-}\boldsymbol{1})} = -1.970~\mathrm{eV} and R_S(C70-1) = -2.300 eVR_{S(C70\mbox{-}\boldsymbol{1})}= -2.300~\mathrm{eV}. Molecular mechanics force field method calculations established that the binding pattern of C₇₀ towards 1 occurs in the side-on rather than end-on orientation, and that the C₇₀-1 complex gains 5.23 kJ⋅mol⁻¹ of extra stabilization energy with this side-on geometrical arrangement.     

The Enthalpy of Solution of the Alanine-Based Ionic Liquid [C<Subscript>4</Subscript>mim][Ala]

The molar enthalpies of solution of an alanine-based ionic liquid (IL) [C₄mim][Ala], 1-butyl-3-methylimidazolium alanine, containing various amount of water and various molalities Δ_sol H _m(wc), were measured with a solution-reaction isoperibol calorimeter at (298.15±0.01) K, where wc denotes water content. According to Archer’s method, the standard molar enthalpies of solution of [C₄mim][Ala] containing known amounts of water, D_solH_m^o(wc)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{wc}) , were obtained. In order to eliminate the effect of the small amount of residual water in the source [C₄mim][Ala], a linear fitting of D_solH_m^o(wc)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{wc}) against water content was carried out, yielding a good straight line where the intercept is the standard molar enthalpy of solution of anhydrous [C₄mim][Ala], D_solH_m^o(pure IL)=-(61.42±0.08)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{pure}\ \mathrm{IL})=-(61.42\pm 0.08) kJ⋅mol⁻¹. The hydration enthalpy of the alanine anion [Ala]⁻ was estimated using Glasser’s lattice energy theory.     

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.     

Intermolecular Interactions in Ternary Glycerol–Sample–H<Subscript>2</Subscript>O: Towards Understanding the Hofmeister Series (V)

We studied the intermolecular interactions in ternary glycerol (Gly)–sample (S)–H₂O systems at 25 °C. By measuring the excess partial molar enthalpy of Gly, H_Gly^EH_{\mathrm{Gly}}^{\mathrm{E}}, we evaluated the Gly–Gly enthalpic interaction, H_Gly-Gly^EH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}}, in the presence of various samples (S). For S, tert-butanol (TBA), 1-propanol (1P), urea (UR), NaF, NaCl, NaBr, NaI, and NaSCN were used. It was found that hydrophobes (TBA and 1P) reduce the values of H_Gly-Gly^EH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}} considerably, but a hydrophile (UR) had very little effect on H_Gly-Gly^EH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}}. The results with Na salts indicated that there have very little effect on H_Gly-Gly^EH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}}. This contrasts with our earlier studies on 1P–S–H₂O in that Na⁺, F⁻ and Cl⁻ are found as hydration centers from the induced changes on H_IP-IP^EH_{\mathrm{IP}\mbox{--}\mathrm{IP}}^{\mathrm{E}} in the presence of S, while Br⁻, I⁻, and SCN⁻ are found to act as hydrophiles. In comparison with the Hofmeister ranking of these ions, the kosmotropes are hydration centers and the more kosmotropic the higher the hydration number, consistent with the original Hofmeister’s concept of “H₂O withdrawing power.” Br⁻, I⁻ and SCN⁻, on the other hand, acted as hydrophiles and the more chaotropic they are the more hydrophilic. These observations hint that whatever effect each individual ion has on H₂O, it is sensitive only to hydrophobes (such as 1P) but not to hydrophiles (such as Gly). This may have an important bearing towards understanding the Hofmeister series, since biopolymers are amphiphilic and their surfaces are covered by hydrophobic as well as hydrophilic parts.     

Kinetics and mechanism of oxidation of aquaethylenediaminetetraacetatocobaltate(II) by <Emphasis Type="Italic">N</Emphasis>-bromosuccinimide in aqueous acidic solution

The oxidation of aquaethylenediaminetetraacetatocobaltate(II) [Co(EDTA)(H₂O)]⁻² by N-bromosuccinimide (NBS) in aqueous solution has been studied spectrophotometrically over the pH 6.10–7.02 range at 25 °C. The reaction is first-order with respect to complex and the oxidant, and it obeys the following rate law:

Constant current anodic stripping chronopotentiometric determination of uranium in uranium mineral ores via accumulation of K<Subscript>2</Subscript>UO<Subscript>2</Subscript>[Fe(CN)<Subscript>6</Subscript>] on the palladium plated aluminum electrode

In the present work the uranyl hexacyanoferrate (K₂UO₂[Fe(CN)₆]) is deposited on the palladized aluminum (Pd-Al) electrode from a \textUO₂^{2 +} + \textFe( \textCN )₆ ^{- 3} {\text{UO}}_{2}^{2 + } + {\text{Fe}}\left( {\text{CN}} \right)_{6}^{ - 3} solution. Then the anodic stripping chronopotentiometry (ASCP) was used to strip the K₂UO₂[Fe(CN)₆] from the Pd-Al surface. The operational conditions including: pH, K₃Fe(CN)₆ concentration, deposition potential, deposition time and stripping current were optimized. The ASCP calibration graph was linear in concentration range 10–460 μM. of \textUO₂^{2 +} {\text{UO}}_{2}^{2 + } and the detection limit was 8.5 μM. The interference of some concomitant ions during the deposition process of K₂UO₂[Fe(CN)₆] was studied. The proposed method was successfully applied for analysis of some uranium mineral ores.     

Determination of the Hydrolysis Constants and Solubility Product of Chromium(III) from Reduction of Dichromate Solutions by ICP-OES and UV–Visible Spectroscopy

The determination of equilibrium constants is difficult when several chemical species are simultaneously present in solution. In this investigation, optical emission spectroscopic determinations of chromium(III) concentration in a 10⁻⁴ mol⋅dm⁻³ solution, prepared from K₂Cr₂O₇ reduced in HNO₃ or HCl media, were used to construct the pCr_(aq)–pC _H diagram. This diagram was used to calculate the pC _H borderline of precipitation, to estimate the solubility product (log₁₀K_sp,Cr(OH)3^*)(\log_{10}K_{\mathrm{sp,Cr(OH)}_{3}}^{*}), and the hydrolysis constants (log₁₀b_Cr,H^*,log₁₀b_Cr,2H^*(\log_{10}\beta_{\mathrm{Cr,H}}^{*},\log_{10}\beta_{\mathrm{Cr,2H}}^{*}, and log₁₀b_Cr,3H^*)\log_{10}\beta_{\mathrm{Cr,3H}}^{*}) of Cr(III). The hydrolysis constants were also calculated using the SQUAD and SUPERQUAD software, along with the average ligand number method. UV-Vis absorption data and associated variables were used in SQUAD, SUPERQUAD, and the average ligand calculations. Results are: 9.00±0.04 for the pC _H at the onset of precipitation, 12.40 for log₁₀K_sp,Cr(OH)3^*\log_{10}K_{\mathrm{sp,Cr(OH)}_{3}}^{*}, −3.52±0.02 for log₁₀b_Cr,H^*\log_{10}\beta_{\mathrm{Cr,H}}^{*}, −9.30±0.87 for log₁₀b_Cr,2H^*\log_{10}\beta_{\mathrm{Cr,2H}}^{*} and −17.18±0.16 for log₁₀b_Cr,3H^*\log_{10}\beta_{\mathrm{Cr,3H}}^{*}, respectively. All methods produced essentially the same values for the hydrolysis constants of Cr(III).     

PuPO<Subscript>4</Subscript>(cr,hyd.) Solubility Product and Pu<Superscript>3+</Superscript> Complexes with Phosphate and Ethylenediaminetetraacetic Acid

To determine the solubility product of PuPO₄(cr, hyd.) and the complexation constants of Pu(III) with phosphate and EDTA, the solubility of PuPO₄(cr, hyd.) was investigated as a function of: (1) time and pH (varied from 1.0 to 12.0), and at a fixed 0.00032 mol⋅L⁻¹ phosphate concentration; (2) NaH₂PO₄ concentrations varying from 0.0001 mol⋅L⁻¹ to 1.0 mol⋅L⁻¹ and at a fixed pH of 2.5; (3) time and pH (varied from 1.3 to 13.0) at fixed concentrations of 0.00032 mol⋅L⁻¹ phosphate and 0.0004 mol⋅L⁻¹ or 0.002 mol⋅L⁻¹ Na₂H₂EDTA; and (4) Na₂H₂EDTA concentrations varying from 0.00005 mol⋅L⁻¹ to 0.0256 mol⋅L⁻¹ at a fixed 0.00032 mol⋅L⁻¹ phosphate concentration and at pH values of approximately 3.5, 10.6, and 12.6. A combination of solvent extraction and spectrophotometric techniques confirmed that the use of hydroquinone and Na₂S₂O₄ helped maintain the Pu as Pu(III). The solubility data were interpreted using the Pitzer and SIT models, and both provided similar values for the solubility product of PuPO₄(cr, hyd.) and for the formation constant of PuEDTA⁻. The log ₁₀ of the solubility product of PuPO₄(cr, hyd.) [PuPO₄(cr, hyd.) \rightleftarrows\rightleftarrows Pu³⁺+PO₄^3-\mathrm{Pu}^{3+}+\mathrm{PO}_{4}^{3-}] was determined to be −(24.42±0.38). Pitzer modeling showed that phosphate interactions with Pu³⁺ were extremely weak and did not require any phosphate complexes [e.g., PuPO₄(aq), PuH₂PO₄²⁺\mathrm{PuH}_{2}\mathrm{PO}_{4}^{2+}, Pu(H₂PO₄)₂⁺\mathrm{Pu(H}_{2}\mathrm{PO}_{4})_{2}^{+}, Pu(H₂PO₄)₃(aq), and Pu(H₂PO₄)₄^-\mathrm{Pu(H}_{2}\mathrm{PO}_{4})_{4}^{-}] as proposed in existing literature, to explain the experimental solubility data. SIT modeling, however, required the inclusion of PuH₂PO₄²⁺\mathrm{PuH}_{2}\mathrm{PO}_{4}^{2+} to explain the data in high NaH₂PO₄ concentrations; this illustrates the differences one can expect when using these two different chemical models to interpret the data. Of the Pu(III)-EDTA species, only PuEDTA⁻ was needed to interpret the experimental data over a large range of pH values (1.3–12.9) and EDTA concentrations (0.00005–0.256 mol⋅L⁻¹). Calculations based on density functional theory support the existence of PuEDTA⁻ (with prospective stoichiometry as Pu(OH₂)₃EDTA⁻) as the chemically and structurally stable species. The log ₁₀ value of the complexation constant for the formation of PuEDTA⁻ [ Pu³⁺+EDTA^4-\rightleftarrows PuEDTA^-\mathrm{Pu}^{3+}+\mathrm{EDTA}^{4-}\rightleftarrows \mathrm{PuEDTA}^{-}] determined in this study is −20.15±0.59. The data also showed that PuHEDTA(aq), Pu(EDTA)₄^5-\mathrm{Pu(EDTA)}_{4}^{5-}, Pu(EDTA)(HEDTA)⁴⁻, Pu(EDTA)(H₂EDTA)³⁻, and Pu(EDTA)(H₃EDTA)²⁻, although reported in the literature, have no region of dominance in the experimental range of variables investigated in this study.     

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.     

Ab initio investigation of the lower-energy candidate structures for (H<Subscript>2</Subscript>O)<Subscript>10</Subscript><Superscript>+</Superscript> water cluster

Low-lying structures of water cationic clusters and the compounds with the OH radical have become a hot topic in recent years. We here investigate the cluster \( {\left({\mathrm{H}}_2\mathrm{O}\right)}_{10}^{+} \) and calculate its ideal structures by the quantum chemical calculation together with the particle swarm optimization method. We analyzed the properties of the obtained lower-energy isomers of \( {\left({\mathrm{H}}_2\mathrm{O}\right)}_{10}^{+} \). Their energies are further re-optimized and demonstrated at three different methods with two basis sets. Based on our numerical calculations, a new cage-like structure of \( {\left({\mathrm{H}}_2\mathrm{O}\right)}_{10}^{+} \) with the lowest energy is obtained at MP2/aug-cc-pVDZ level. Our results showed the comparison of energy order at different conditions and demonstrated the influence of temperature on the relative Gibbs energy and IR spectra. Moreover, we also contained the molecule orbitals to discuss the stability of these representative isomers.     

Kinetics of Oxidation of L-Valine by a Copper(III) Periodate Complex in Alkaline Medium

The kinetics of oxidation of L-valine by a copper(III) periodate complex was studied spectrophotometrically. The inverse second-order dependency on [OH⁻] was due to the formation of the protonated diperiodatocuprate(III) complex ([Cu(H₃IO₆)₂]⁻) from [Cu(H₂IO₆)₂]³⁻. The retarding effect of initially added periodate suggests that the dissociation of copper(III) periodate complex occurs in a pre-equilibrium step in which it loses one periodate ligand. Among the various forms of copper(III) periodate complex occurring in alkaline solutions, the monoperiodatocuprate(III) appears to be the active form of copper(III) periodate complex. The observed second-order dependency of [L-valine] on the rate of reaction appears to result from formation of a complex with monoperiodatocuprate(III) followed by oxidation in a slow step. A suitable mechanism consistent with experimental results was proposed. The rate law was derived as:

Kinetics of the uninhibited and ethanol-inhibited CoO,Co<Subscript>2</Subscript>O<Subscript>3</Subscript> and Ni<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyzed autoxidation of sulfur(IV) in alkaline medium

For getting an insight into the mechanism of atmospheric autoxidation of sulfur(IV), the kinetics of this autoxidation reaction catalyzed by CoO, Co₂O₃ and Ni₂O₃ in buffered alkaline medium has been studied, and found to be defined by Eqs. I and II for catalysis by cobalt oxides and Ni₂O₃, respectively.

Kinetic Study of the Oxidation of N,N-Dimethylethanolamine by Bis(Hydrogenperiodato)Argentate(III) in Aqueous Solution

The oxidation of N,N-dimethylethanolamine (DMEA) by bis(hydrogenperiodato) argentate(III) ([Ag(HIO₆)₂]⁵⁻) was studied in aqueous alkaline medium. Formaldehyde and dimethylamine were identified as the major oxidation products after the oxidation of DMEA. The oxidation kinetics was followed spectrophotometrically in the temperature range of 25.0 °C–40.0 °C. It was found that the reaction was first order in [Ag(III)]; the oberved first-order rate constants k _obsd as functions of [DMEA], [OH⁻] and total concentration of periodate ([IO₄^-]_tot[\mathrm{IO}_{4}^{-}]_{\mathrm{tot}}) were analyzed and were revealed to follow a rate expression: k_obsd = (k₁ +k₂[OH^-])K₁K₂[DMEA]/{f([OH^-])[IO₄^-]_tot+ K₁ + K₁K₂[DMEA]}k_{\mathrm{obsd}} = (k_{1} +k_{2}[\mathrm{OH}^{-}])K_{1}K_{2}[\mathrm{DMEA}]/\{f([\mathrm{OH}^{-}])[\mathrm{IO}_{4}^{-}]_{\mathrm{tot}}+ K_{1} + K_{1}K_{2}[\mathrm{DMEA}]\}. Rate constants k ₁ and k ₂ and equilibrium constant K ₂ were derived; activation parameters corresponding to k ₁ and k ₂ were computed. In the proposed reaction mechanism, a peridato-Ag(III)-DMEA ternary complex is formed indirectly through a reactive intermediate species [Ag(HIO₆)(OH)(H₂O)]²⁻. In subsequent rate-determining steps as described by k ₁ and k ₂, the ternary complex decays to Ag(I) through two reaction pathways: one of which is spontaneous and the other is prompted by an OH⁻.     

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.     

Raman and Infrared Spectroscopic Investigation of Speciation in BeSO<Subscript>4</Subscript>(aq)

Measurements have been made of the Raman spectra of aqueous solutions of Be(ClO₄)₂, BeCl₂, (NH₄)₂SO₄ and BeSO₄ to 50 cm⁻¹. In some cases low concentrations (0.000770 mol⋅kg⁻¹) have been used and two temperatures (23 and 40 °C) were studied. In BeSO₄(aq), the ν ₁-SO₄^2-\mathrm{SO}_{4}^{2-} mode at 980 cm⁻¹ broadens with increasing concentration and shifts to higher wavenumbers. At the same time, a band at 1014 cm⁻¹ is detectable with this mode being assigned to [BeOSO₃], an inner-sphere complex (ISC). Confirmation of this assignment is provided by the simultaneous appearance of stretching bands for the Be²⁺-OSO₃^2-\mathrm{Be}^{2+}\mbox{-}\mathrm{OSO}_{3}^{2-} bond of the complex at 240 cm⁻¹ and for the BeO₄ skeleton mode of the [(H₂O)₃BeOSO₃] unit at 498 cm⁻¹. The ISC concentration increases with higher temperatures. The similarity of the n₁-SO₄^2-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} Raman bands for BeSO₄ in H₂O and D₂O is further strong evidence for formation of an ISC. After subtraction of the ISC component at 1014 cm⁻¹, the n₁-SO₄^2-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} band in BeSO₄(aq) showed systematic differences from that in (NH₄)₂SO₄(aq). This is consistent with a n₁-SO₄^2-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} mode at 982.7 cm⁻¹ that can be assigned to the occurrence of an outer-sphere complex ion (OSCs). These observations are shown to be in agreement with results derived from previous relaxation measurements. Infrared spectroscopic data show features that are also consistent with a beryllium sulfato complex such as the appearance of a broad and weak n₁-SO₄^2-\nu_{1}\mbox{-}\mathrm{SO}_{4}^{2-} mode at ∼1014 cm⁻¹, normally infrared forbidden, and a broad and asymmetric n₃-SO₄^2-\nu_{3}\mbox{-}\mathrm{SO}_{4}^{2-} band contour which could be fitted with four band components (including n₃-SO₄^2-(aq)\nu_{3}\mbox{-}\mathrm{SO}_{4}^{2-}(\mathrm{aq})). The formation of ISCs in BeSO₄(aq) is much more pronounced than in the similar MgSO₄(aq) system studied recently.     

Electroactive Polymerization Behaviors of Fused-Pentagon Chlorofullerenes: <Superscript>#1809</Superscript>C<Subscript>60</Subscript>Cl<Subscript>8</Subscript> and <Superscript>#271</Superscript>C<Subscript>50</Subscript>Cl<Subscript>10</Subscript>

The fullerenes that violate isolated pentagon rule (IPR) have unusual electronic properties resulting from their fused-pentagon structures. Numerous non-IPR fullerenes have now been captured by chlorination, affording opportunity to go insight into the properties involved in non-IPR fullerenes in the forms of chlorofullerenes (CFs). Here cyclic voltammetry (CV) is employed to probe the electrochemical properties of non-IPR ^#1809C₆₀Cl₈ in comparison with those of ^#271C₅₀Cl₁₀. Differing from IPR-satisfying CFs such as C₆₀Cl₈ and C₆₀Cl₁₀ (referring to I _h-symmetric C₆₀), the two non-IPR CFs exhibit divergent electroactive polymerization characters. In addition, the electrocatalytic effect of ferrocene that is otherwise employed as internal reference has been shown in the CV process of CFs.     

Kinetic and mechanistic studies on the substitution of aqua ligands from <Emphasis Type="Italic">cis</Emphasis>-diaqua-<Emphasis Type="Italic">bis</Emphasis>-(bypyridyl)-ruthenium(II) ion by vic-dioximes

Kinetics of aqua ligand substitution from cis-[Ru(bpy)₂(H₂O)₂]²⁺ by three vicinal dioximes, namely dimethylglyoxime (L¹H), 1,2-cyclohexane dionedioxime (L²H) and α-furil dioxime (L³H) have been studied spectrophotometrically in the 45–60 °C temperature range. The rate constants increase with increasing dioxime concentration and approach a limiting condition. We propose the following rate law for the reaction in the 3.5–5.5 pH range: where k ₂ is the interchange rate constant from outer sphere to inner sphere complex and K _E is the outer sphere association equilibrium constant. Activation parameters were calculated from the Eyring plots for all three systems: ΔH ^≠ = 59.2 ± 8.8, 63.1 ± 6.8 and 69.7 ± 8.5 kJ mol⁻¹, ΔS ^≠ = −122 ± 27, −117 ± 21 and −99 ± 26 J K⁻¹ mol⁻¹ for L¹H, L²H and L³H, respectively. An associative interchange mechanism is proposed for the substitution process. Thermodynamic parameters calculated from the temperature dependence of the outer sphere association equilibrium constants give negative ΔG ⁰ values for all the systems studied at all the temperatures (ΔH ⁰ = 30.05 ± 2.5, 18.9 ± 1.1 and 11.8 ± 0.2 kJ mol⁻¹; ΔS ⁰ = 123 ± 8, 94 ± 3 and 74 ± 1 J K⁻¹ mol⁻¹ for L¹H, L²H and L³H, respectively), which also support our proposition.     

Sorption of Light Fullerenes (C<Subscript>60</Subscript> and C<Subscript>70</Subscript>) on Materials Prepared by Sublimation of Graphite Rods

Sorption of fullerenes C₆₀ and C₇₀ from o-xylene, toluene, and o-dichlorobenzene solutions under static conditions on a sorbent prepared by sublimation of graphite rods was studied. The sorption isotherms of both fullerenes at 25°C were measured.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 345–346.Original Russian Text Copyright © 2005 by Semenov, Arapov, Charykov, Nekrasov, Alekhin, Gerasimov, Seregin.