酸性化学镀镍磷合金的动力学机理

通过极化曲线研究了3种不同溶液（阴极液、阳极液和完整镀液）的电化学行为,测定了主盐、还原剂浓度以及镀液pH和体系温度对化学镀镍沉积速率的影响. 与直接在镁合金上化学镀镍并使用重量分析法得到的沉积速率相比较发现,完整镀液体系的极化曲线才能真实地反映化学镀镍的沉积过程,其过程不能简单视为由彼此完全独立毫无关联的阴阳极半反应构成. 根据Butler-Volmer公式,本化学镀液体系的化学镀镍过程属混合控制,其表观反应活化能为42.89 kJ·mol^-1.     

Green Oxidations. Manganese(II) Sulfate Aided Oxidations of Organic Compounds by Potassium Permanganate

Summary. The oxidation of arenes and sulfides by potassium permanganate was accomplished in good yields under solvent free and heterogeneous conditions when manganese(II) sulfate is used as a solid support. After extraction of the organic products, the inorganic products can be reoxidized to permanganate. This result is important because it provides an approach to oxidation reactions that is, in theory, infinitely sustainable.     

Solid Phase Derivatizations in HPLC: Polymeric Permanganate Oxidations of Alcohols and Aldehydes in HPLC-SPR

Abstract

On-line or off-line oxidations of various alcohols, aldehydes, and ketones can now be performed in conjunction with high performance liquid chromatography (HPLC), utilizing a newly developed polymeric permanganate solid phase reactor (SPR). These derivatization reactions are compatible with most reversed phase and normal phase solvents for HPLC separations, and many of these oxidations can be accomplished in real-time, on-line, at or above room temperature. Such HPLC-SPR approaches for chemical modifications and derivatizations of various oxidizable analytes provide a useful and quite practical newer approach for the HPLC-ultraviolet (UV) detection of appropriate analyte species. Difference chromatography, often with improved UV detection, can be used to confirm the suspected presence of a particular oxidizable analyte in a complex sample matrix. All of these solid phase derivatizations utilize conventional, commercially available HPLC instruments and accessories. These HPLC-SPR oxidation methods for chemical derivatization have also been applied to certain real world samples, in order to demonstrate the overall value and applicability of such analytical approaches.     

Kinetics and Mechanism of the Autocatalyzed Oxidation of Theophylline by Permanganate in Aqueous Perchloric Acid Medium

The reaction kinetics for the oxidation of theophylline by permanganate ions have been investigated in perchloric acid medium using spectrophotometric techniques at 25?^°C, and at constant ionic strength 1.60 mol?dm^?3, under pseudo first order conditions. An autocatalyzed reaction is observed due to one of the products formed is Mn(II). The orders with respect to theophylline and Mn(VII) were both found to be unity, whereas fractional order is observed with respect to the autocatalyst, Mn(II). The rate of the reaction increases as the concentration of acid increases, but the order with respect to acid concentration is less than unity. The influence of temperature on the rate of reaction was studied. Based on the experimental results a suitable mechanism is proposed. The activation and thermodynamic parameters were determined with respect to slow reaction step.     

Kinetics and Mechanism of Cetyltrimethylammonium Bromide Catalyzed N-Bromosuccinimide Oxidation of D-Mannose in Acidic Medium

The kinetics and mechanism of N-bromosuccinimide (NBS) oxidation of D-mannose in the absence and presence of cetyltrimethylammonium bromide (CTAB) in acidic media have been studied under the condition [D-mannose]_T ? [NBS]_T at 40°C. Under the kinetic conditions, both the slower uncatalyzed and faster catalyzed paths go on. Both the paths show the fractional and first order dependence on [D-mannose] and [NBS]_T, respectively. The rate decreased with increase in acidity. Neither succinimide (NHS) nor Hg(II) influenced the reaction rate. Activation parameters of the reactions were determined by studying the reaction at different temperatures (30–50°C). The influence of salts on the reaction rate was also studied. CTAB accelerates the reactions and the observed effects have been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. In the reaction, approximately 1 mole of NBS oxidized one mole of D-mannose. A reaction scheme of the oxidation of D-mannose by NBS was found to be in consistent with the rate law and the reaction stoichiometry.     

Kinetics and Mechanism of Oxidation of l‐Histidine by Permanganate Ions in Sulfuric Acid Medium

The reaction kinetics for the oxidation of l ‐histidine by permanganate ions have been investigated spectrophotometrically in sulfuric acid medium at constant ionic strength and temperature. The order with respect to permanganate ions was found to be unity and second in acid concentration, whereas a fractional order is observed with respect to histidine. The reaction was observed to proceed through formation of a 1:1 intermediate complex between oxidant and substrate. The effect of the acid concentration suggests that the reaction is acid catalyzed. Increasing the ionic strength has no significant effect on the rate. The influence of temperature on the rate of reaction was studied. The presence of metal ion catalysts was found to accelerate the oxidation rate, and the order of effectiveness of the ions was Cu²⁺ > Ni²⁺ > Zn²⁺. The final oxidation products were identified as aldehyde (2‐imidazole acetaldehyde), ammonium ion, manganese(II), and carbon dioxide. Based on the kinetic results, a plausible reaction mechanism is proposed. The activation parameters were determined and discussed with respect to a slow reaction step.     

探究苯与酸性高锰酸钾溶液的褪色反应

人教版高中教材《化学2》明确指出苯不能使酸性高锰酸钾溶液褪色。但在实验中多次发现苯与酸性高锰酸钾溶液混合后放置一段时间能够褪色。为探讨这一问题，设计了以光照或黑暗、加酸或不加酸为条件，利用紫外-可见分光光度计对放置不同时间后的混合液体进行测试，并对反应后生成的沉淀物进行XRD表征的实验方案。通过对实验数据的综合分析提出了苯与酸性高锰酸钾溶液褪色反应的可能反应机理。     

Formal Bleaching Kinetics of Acid Blue 80 in Weakly Acidic,Neutral, and Basic Aqueous Media

General kinetic relations were established for the first step of oxidation of Acid Blue 80 in weakly acidic, neutral and basic media in the following systems: Fe²⁺-H₂O₂, Mn²⁺-HCO₃ ^--H₂O₂, and Cu²⁺-phenanthroline-H₂O₂. The rate constant for the reaction of hydroxyl radical with the dye and the dependence of the degree of bleaching upon oxidant and catalyst concentrations were determined.     

Kinetics and Mechanism of Oxidation of Captopril by Hexacyanoferrate(III) in Aqueous Acidic Medium

Captopril (Capt, 1-[2(s)-3-mercapto-2-methyl-1-oxopropyl]-l-proline) was oxidized by hexacyanoferrate(III) (HCF). The kinetics of the oxidation was studied spectrophotometrically at 420 nm. The reaction was found to be first order in [HCF] and [Capt] and to have a negative fractional order in [H⁺]. Oxidation was followed by generation of a free radical from captopril, and the oxidative product of catpotpril was identified as captopril disulfide. It was characterized by IR, GCMS and ESI–MS spectra. Initially added product, hexacyanoferrate(II), retarded the rate of reaction with an order of ?0.5. The retarding effect of added [H⁺] indicated that unprotonated hexacyanoferrate(III) is the active species. A suitable free radical mechanism was proposed. The rate law was derived and verified.     

Rearrangements of Neoclovene Epoxides in Acidic Media

Rearrangements of neoclovene epoxides in the presence of a solid superacid ZrO₂/SO₄ ^{2 -} and in formic acid were investigated. In the latter case a ketone was obtained with a previously unknown carbon skeleton. The most probable pathway of its formation was derived from calculations by molecular mechanics and quantum-chemical methods.     

Kinetics and Mechanism of Oxidation of Dimethyl Sulfoxide with Benzoyl Peroxide in Superbasic Media

Oxidation of dimethyl sulfoxide with benzoyl peroxide in some dipolar aprotic solvents and superbasic media was studied. The kinetic parameters were correlated with the main physicochemical characteristics of solvents. The oxidation rate grows with increasing donor number and polarizability of the solvent. A two-step scheme of dimethyl sulfoxide oxidation with benzoyl peroxide in superbasic media was suggested, involving preliminary cleavage of the peroxide to perbenzoate with the base. In the reaction, sodium tert-butylate is preferable over sodium hydroxide.     

Kinetics and Mechanism of Oxidation of Adipic Acid by Ce(IV) Ion in Acidic Medium

Kinetic study of oxidation of adipic acid by Ce(IV) ion in aqueous solution of sulphuric acid shows that the reaction follows first order kinetics in both Ce(IV) and adipic acid and the over all reaction order ascertained is two. The specific rate constant increases with an increase in the concentration of adipic acid. Effects of hydrogen ion concentration, bisulphate ion and temperature have been studied in detail. Various kinetic parameters have been computed. The experimental findings are consistent with the mechanism involving rapid resersible formation of an activated complex between Ce(IV) and adipic acid followed by a rate determining step involving C-C bond fission.     

Synthesis of Pd-Cu Bimetallic Electrocatalyst for Ethylene Glycol and Glycerol Oxidations in Alkaline Media

PdCu/C (XC-72) electrocatalyst was synthesized by a chemical reduction method using ethylene glycol as reaction media, polyvinylpyrrolidone as surfactant and sodium borohydride as reducing agent. Vulcan carbon XC-72 was employed as support and added through the PdCu synthesis procedure; further, Pd commercial (Pd/C, 20% ETEK) was used for comparison purposes. Physicochemical characterization consisted in XRD, XRF, EDS and TEM analyses. TEM micrographs showed the presence of semi-spherical nanoparticles with a particle distribution around 6 nm. X-ray diffraction patterns showed the typical face-centered cubic structure of Pd materials for commercial Pd and revealed a low crystallinity for PdCu/C. The XRF analysis showed a mass metal composition of 81% Pd and 19% Cu. EDS analysis was made to single particles exhibiting an average elemental composition of 92% Pd and 8% Cu. The electrocatalytic activity of PdCu/C and Pd/C was evaluated by cyclic voltammetry experiments toward ethylene glycol and glycerol oxidations using three concentrations (0.1, 1 and 3 M) and 0.3 M KOH as electrolyte. These experiments exhibited the superior performance of PdCu compared with commercial Pd by means of current densities associated to the electro-oxidation reactions where values at least 3-fold higher than Pd/C were found.     

Kinetics and Mechanism of Electron Transfer Reactions: Oxidation of Crotyl Alcohol by Peroxomonosulfate in Aqueous Acidic Medium

The kinetics and mechanism of oxidation of crotyl alcohol by peroxomonosulfate has been studied, and the species of the peroxomonosulfate are discussed to find out the role of activated species. A plausible reaction mechanism is suggested, and a derived rate law corresponds to all experimental observations. The activation parameters such as energy and entropy of activation have been calculated as 37.21 ± 0.5 kJ mol⁻¹ and −148.91 ± 2.7 J K⁻¹ mol⁻¹, respectively, by employing the Eyring plot.     

Synthesis and Crystal Structures of Copper(I) Complexes with N-Allylhexamethylenetetraminium Chloride Obtained in Different Acidic Media

The crystals of [(CH₂)₆N₄(C₃H₅)]Cu₂Cl₃ (I), [(CH₂)₆N₄(C₃H₅)]Cu₂Cl₃ (II), and [(CH₂)₆N₄(C₃H₅)]CuCl₂ (III) complexes were electrochemically synthesized (ac) from CuCl₂ · 2H₂O and N-allylhexamethylenetetraminium chloride in ethanol solutions at pH 6, 4.5, and 3. Their structures were determined using X-ray diffraction analysis (DARCh diffractometer, MoK radiation, /2 scan mode). Complex Icrystallizes in the monoclinic system: space group A2/a, a = 24.812(6) Å, b = 8.855(3) Å, c = 12.080(2) Å, = 89.21(3)°, and Z = 8. Complex II crystallizes in the triclinic system: space group P , a = 7.618(2) Å, b = 7.048(2) Å, c = 13.150(3) Å, = 97.50(2)°, = 92.70(2)°, = 100.74(2)°, and Z = 2. The crystals of complex III are orthorhombic: space group Pmn2₁, a = 7.478(2) Å, b = 8.827(2) Å, c = 9.662(3) Å, Z = 2. The organic cation in complex I acts as a tridentate ,,-ligand; that in complex II, as a bidentate ,-ligand. In complex III, the organic cation is involved in coordination with the copper(I) atom only through one nitrogen atom.     

Characteristics of Template Formation in Silica in Acidic Media

Characteristics of template formation in silica at pH < 0.1 in the presence of a surface active substance (cetyltrimethylammonium bromide or chloride) have been investigated. Depending on the acidity of the reaction medium and some other factors, the synthesis of spontaneously growing particles of templated silica at interfacial surfaces led to the formation of fibers, spirals, spheres, and other forms, most of which appeared as hexagonally ordered bodies of revolution. It is possible to detemplate these forms of silica and to transform them to mesoporous molecular sieves without destroying their structures.     

高效液相色谱-高锰酸钾氧化化学发光法测定水中的痕量苯二酚

基于酸性介质中甲酸对高锰酸钾-苯二酚氧化发光反应的增敏作用建立了高效液相色谱-化学发光柱后检测苯二酚的新方法。优化了高锰酸钾-苯二酚氧化发光反应及高效液相色谱分离苯二酚的条件,用甲醇-0.1 mmol/L β-环糊精水溶液(体积比为30∶70) 作为流动相可实现对水中3种苯二酚异构体的分离,且能与高锰酸钾-苯二酚氧化化学发光反应条件很好地偶合。对所测定的苯二酚异构体,方法的线性范围达两个数量级;以信噪比为3测得邻、间、对苯二酚的检出限(n=3)分别为:5.2,4.7,3.2 μg/L,对质量浓度均为0.10 mg/L的3种苯二酚混合溶液连续测定11次,邻、间、对苯二酚的相对标准偏差分别为2.8%,3.4%,6.5%。将该方法与固相萃取技术相结合,对河水中的痕量苯二酚进行了测定,加标回收率为92.1%~95.4%。     

The Growth of Phosphonium Gold Nanoparticles in Alkaline Media: Kinetics and Mechanism of the Process

Colloid Journal - It has been found that the addition of ammonia water to a gold sol obtained by the Duff method induces the growth of the gold particles. The growth kinetics of such particles in...     

Kinetics and Mechanism of the Liquid-Phase Oxidation of 10-Dihydro-9-ketoanthracene in Basic Aprotic Media

The kinetics of the liquid-phase oxidation 10-dihydro-9-ketoanthracene (anthrone) by molecular oxygen was studied in dimethylsulfoxide. Anthrone was found to undergo facile oxidation to give anthraquinone in virtually quantitative yield in this highly basic, polar solvent, while the oxidation rates are much lower in acetonitrile and dimethylformamide, which are less polar solvents. A kinetic scheme for this reaction was proposed.