Cathodic Hydrogen Evolution from Aqueous Solutions of Acetic Acid

In continuation of the work on establishing hydrogen donors in the hydrogen evolution reaction from different acid molecules, cathodic evolution of hydrogen on silver is investigated from solutions of monobasic acetic acid with the aim to establish the origin of reduced hydrogen. Solutions of 0.2 M acetic acid with 0.2 M perchloric acid, neutralized to different pH values by NaOH, are used. The earlier established criterion is used for discerning between two possible hydrogen evolution mechanisms: (1) from dissociated hydrogen ions and (2) from undissociated hydrogen atoms in the molecule. At medium pH values, the undissociated acid molecules participate as hydrogen donors. Rate constants for reactions 1 and 2, evaluated at a potential of –800 mV (SCE), at which the entire pH range can be scanned, are 2.9 × 10^–6 and 1.9 × 10^–8.     

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.     

苯在Pluronic F127和P123胶束水溶液中的增溶动力学

发展了不分离胶束的增溶动力学数据分析模型,以此考察苯在F127和P123胶束水溶液中的增溶动力学行为.实验发现,这二种胶束增溶苯的速度较快,温度升高进一步促进了增溶.     

Radiation-Stimulated Oxidation Reactions of Oxo Anions in Aqueous Solutions

The common features of oxidation processes for inorganic oxo anions under the action of ionizing radiation are considered. The radiation-stimulated oxidation reactions of lower nitrogen, phosphorus, arsenic, and sulfur oxo anions occur via a chain mechanism. The kinetics of these processes can be explained in terms of the peroxide oxidation theory. A correlation between the kinetic and thermodynamic characteristics of the assumed rate-determining step is observed, thus proving the uniformity of oxidation mechanisms. Ways to use the processes of interest in practice are proposed.     

Nitrosation of Dodecahydro-closo-Dodecaborate Anions in Aqueous and Nonaqueous Solutions

Nitrosation of dodecahydro-closo-dodecaborate anions with nitrous acid in an aqueous solution and with isoamyl nitrite and nitrosyl chloride in nonaqueous solutions was studied. The main reaction product is the mononitrosoundecahydro-closo-dodecaborate anion. Conditions were selected for the preparation of the nitroso-substituted anion in the highest yield as alkylammonium, tetraphenylphosphonium, and alkali-metal salts. The salts were studied using IR, UV, and ¹¹B NMR spectroscopy.     

Thermodynamics and Kinetics of Bacterial Cellulose Adsorbing Persistent Pollutant from Aqueous Solutions

The adsorption capability of bacterial cellulose(BC) for anionic dye acid fuchsine was studied. Meanwhile, the processes of the adsorption were investignted and fitted by adsorption isotherm models, adsorption thermodynamics and adsorption kinetics models, respectively. The changes of BC before and after adsorbing acid fuchsine were investigated via scanning electron microscopy(SEM) and Fourier transform infrared spectroscopy(FTIR) to further explain the adsorption mechanism. The results show that acid fuchsine could be effectively adsorbed by BC. The adsorption process was fitted well by Langmuir equation and the pseudo-second order kinetics, indicating that the adsorption process was monolayer molecule adsorption with the main action of chemical adsorption. The adsorption process was spontaneous and endothermic. Glucuronic acid groups and hydroxyl groups were responsible for the adsorption of acid fuchsine on BC.     

Kinetics of Ozone-Olefin Reactions in Aqueous Solutions

The kinetics of the reactions of ozone with 12 substituted olefins in aqueous solutions at 293 K are studied by the stopped-flow method. Second-order rate constants are determined for these reactions. The dependence of the reactivity of olefins in H₂O on their structure can be described by the Taft equation.     

次亚磷酸根离子在多晶铂电极上氧化的原位红外光谱研究

次亚磷酸根离子在多晶铂电极上氧化的原位红外光谱研究;电氧化;电催化;SNIFTIRS     

Easily‐prepared Hydroxy‐containing Receptors Recognize Anions in Aqueous Media

Despite their ready availability, O?H groups have received relatively little attention as anion recognition motifs. Here, we report two simple hydroxy‐containing anion receptors that are prepared in two facile steps followed by anion exchange, without the need for chromatographic purification at any stage. These receptors contain a pyridinium bis(amide) motif as well as hydroxyphenyl groups, and bind mono‐ and divalent anions in 9:1 CD₃CN:D₂O, showing a selectivity preference for sulfate. Notably, a “model” receptor that does not contain hydroxy groups shows only very weak sulfate binding in this competitive solvent mixture. In the solid state, X‐ray crystallographic studies show that the receptors tend to form extended assemblies with anions; however, ¹H and DOSY NMR studies as well as molecular dynamics simulations show that only 1:1 complexes are present in solution. Molecular dynamics simulations suggest that one of the receptors suffers from competing intramolecular hydrogen bonding, while another binds partially‐hydrated anions, with the receptor's O?H groups forming hydrogen bonds to water molecules within the anion's coordination sphere.     

Kinetics of Hydrolysis of Inosine in Aqueous Solutions

The kinetics of hydrolysis of inosine was studied in aqueous solution at 353 K over a pH range of 0.45 - 12.13. The decomposition was followed by HPLC. The pH - profile was accounted for by assuming spontaneous water-catalyzed decomposition of the inosine molecules at various degrees of dissociation.     

Kinetics of Glucose Mutarotation in Aqueous Urea Solutions

Kinetics of glucose mutarotation in water-urea mixtures with urea concentrations of 0-15 mol % was studied in the temperature range 283-308 K. It was found for the first time that the rate of mutarotation increases with increasing concentration of urea in water. It was established that urea molecules along with water molecules affect directly the reaction rate via specific solvation. The fact that the activation parameters are almost independent of the concentration of urea was explained in terms of preservation of the structure of the solutions in the composition range studied.     

Compounds of Alkali Metal Anions

Anions of sodium, potassium, rubidium, and cesium are stable both in suitable solvents and in crystalline solids. The latter can be prepared either by cooling a saturated solution or by rapid solvent evaporation. Thermodynamic arguments show that alkali metal anions can probably exist in saturated solutions of the alkali metals in any compatible solvent, but that below saturation, dissociation into the cation and solvated electrons is favored in highly polar solvents such as ammonia. The key to solvent-free salts of the alkali metal anions is stabilization of the cation by incorporation into a suitable crown or cryptand complex. By using such complexes it also appears possible to produce “electride” salts in which the charge of the complexed cation is balanced by a trapped electron. The chemical, electrical, and optical properties of salts of the alkali metal anions and “electrides” could provide useful applications.     

Study on Thermodynamics and Kinetics of Association Interactions between Malachite Green and OP-10 in Aqueous Solutions

The absorption spectrum of malachite green (MG) in a series of aqueous solutions with surfactant octylphenol polyoxyethylene ether (10) (OP-10) has been determined by the UV–Vis spectrophotometer. The association interaction between the MG and nonionic surfactant OP-10 in aqueous solutions resulted in obvious fading of MG. We established the thermodynamics model of association between MG and OP-10, and determined the association equilibrium constant in aqueous solutions. By measuring the absorbance of a series of aqueous solutions which have different molar concentrations of OP-10 but same concentration of MG at different time points, the order and rate constants of association reactions were determined and the reaction kinetics equation was set up.     

Synthesis of a Perfluorinated Phenoxyphosphorane and Conversion to Its Hexacoordinate Anions

We report the synthesis and structural characterization of a neutral P^V Lewis acid, P(OC₆F₅)₅, and salts containing the six-coordinate anions [P(OC₆F₅)₅F]⁻ and [P(OC₆F₅)₆]⁻. The latter anion exhibits a rare example of F–π_arene interactions in both the solid and the solution phase, which has been quantitatively studied by variable-temperature (VT) NMR spectroscopy. The Lewis acid strength of P(OC₆F₅)₅ has been assessed through experimental fluoride ion competition experiments and quantum-chemical calculations of its fluoride ion affinity (FIA) and global electrophilicity index (GEI). Our findings highlight the importance of considering solvent effects in electrophilicity calculations, even when neutral Lewis acids are involved, and show a rare divergence between FIA and GEI trends. The coordinating abilities of the [P(OC₆F₅)₆]⁻ and [P(OC₆F₅)₅F]⁻ anions towards the trityl cation, as a prototypical electrophile, have been assessed.     

次磷酸铝协同硼酸锌阻燃聚乙烯

以次磷酸铝(AHP)和硼酸锌(ZB)为复合阻燃剂,通过熔融共混法制备了阻燃聚乙烯(PE)材料,研究了AHP和ZB对PE的协同阻燃效应。 结果表明,AHP、ZB阻燃剂在PE基体中分散均匀;添加质量分数为25%AHP阻燃剂,PE材料的极限氧指数值(LOI)提升至25%,通过垂直燃烧测试(UL-94(3.2 mm))V-2级,显示出良好的阻燃效果;引入ZB后,材料LOI值呈先升高后下降趋势,在m(AHP):m(ZB)=21:4时,出现峰值,达到27.2%,并通过UL-94(3.2 mm)V-1级;热失重分析(TGA)结果显示,AHP、ZB阻燃剂能同时提高PE材料的热稳定性和成炭率,当m(AHP):m(ZB)=17:8时,残渣率达到25.7%。     

Kinetics of Polyol Oxidation by Ozone in Aqueous Solutions

Spectrophotometry is applied to study the oxidation of ethylene glycol, triethylene glycol, glycerol, etriol, pentaerithritol and mannitol by ozone in aqueous solutions at 277–304 K. Rate constants and activation parameters of the reaction are measured. It is proposed that the oxidation of these alcohols by ozone occurs via the same mechanism. The formation of an intermediate complex is a rate-limiting step in the case of diols; the decomposition of the complex is a rate-limiting step for tri- to hexatomic alcohols.     

Kinetics of Fe(III) → Fe(0) Reduction on Aluminum in Aqueous Solutions

The reduction of iron(III) ions by dispersed aluminum in chloride-containing aqueous solutions and the influence exerted by the initial iron(III) ion concentration and the degree of aluminum dispersion on the kinetics of the process were studied.     

Kinetic Model of Hypophosphite Oxidation on a Nickel Electrode in D_2O Solution

Hypophosphite is one of the most widely used reducing agents in the Ni-electroless deposition. This fact has stimulated the study of anodic oxidation of hypophosphite on a nickel electrode using the probe beam deflection1, electrochemistry, in situ IR2,3 and electrochemical mass spectroscopy4,5. The kinetic model study provides a powerful means of characterizing kinetics and mechanism of electrodic processes. In our recent paper the kinetic model of the Ni-Mo alloy codeposition has been stud…     

Ultrasonic Spectrometry of Aqueous Solutions of Alkyl Maltosides: Kinetics of Micelle Formation and Head‐Group Isomerization

At frequencies between 100 kHz and 400 MHz, ultrasonic attenuation spectra are measured at 25 °C for aqueous solutions of hexyl‐, heptyl‐, octyl‐, nonyl‐, and decyl‐β‐D ‐maltopyranoside as well as of decyl‐α‐D ‐maltopyranoside. The spectra with surfactant concentration c above the relevant critical micelle concentration (cmc) display three relaxation terms with discrete relaxation times. That with a relaxation time between 0.1 and 1.2 μs is due to exchange of monomers between micelles and the suspending phase. It is discussed in the light of the Teubner–Kahlweit–Aniansson–Wall model of the formation/decay kinetics of systems with Gaussian size distribution of micelles. The relaxation parameters are compared to those for solutions of other non‐ionic surfactants, such as alkyl monoglycosides and poly(ethylene glycol) monoalkyl ethers. At c<cmc this low‐frequency relaxation term is missing and at c≈cmc it is broadened, as is characteristic of solutions of oligomeric molecular structures rather than proper micelles. The relaxation terms with relaxation times between 6 and 15 ns and 0.7 and 2.3 ns reveal head‐group rotations around glycosidic angles and isomerization of the exocyclic hydroxymethyl group, respectively. These unimolecular reactions are also examined with a view to solutions of alkyl monoglycosides as well as of glucose and maltose.