Kinetics and mechanism of oxidation of the chromium(III)-DL-aspartic acid complex/periodate reaction. Evidence for iron(II) catalysis

The kinetics of oxidation of the chromium(III)-DL- aspartic acid complex, [CrIIIHL]+ by periodate have been investigated in aqueous medium. In the presence of Fe^II as a catalyst, the following rate law is obeyed:

Kinetics and mechanism of oxidation of malonic acid by chromium(VI) in aqueous perchlorate medium

The kinetics of oxidation of malonic acid, studied in aqueous acid perchlorate, conform to the rate law

Methionine anation of aquachromium(III)

The kinetics of anation of chromium(III) species, [Cr(H₂O)₆]³⁺ and [Cr(H₂O)₅OH]²⁺, by DL-methionine have been studied spectrophotometrically. Effects of varying [methionine]_T, [H⁺], and temperature were investigated. The results are in accord with a mechanism involving a fast 11 outer-sphere association between chromium(III) species and amino acid zwitterion, followed by transformation of the outer-into inner-sphere complex by slow interchange. The rate law consistent with the mechanism is as follows:

Kinetics and mechanism of oxidation of chromium(III)-tetraoxalylurea complex by periodate

A novel chromium(III) complex of tetraoxalylurea was prepared. In aqueous solutions, [Cr^III(H₂L)(H₂O)]⁺ (H₂L = diprotonated tetraoxalylurea) is oxidized by IO ₄ ^– according to the rate law

Substitution of aqua ligands fromcis-diaqua-bis(bipyridyl) ruthenium(II) by 1, 10-phenanthroline in aqueous medium

The kinetics of aqua ligand substitution fromcis-[Ru(bipy)₂(H₂O)₂]²⁺ by 1, 10-phenanthroline (phen) have been studied spectrophotometrically in the 35 to 50°C temperature range. We propose the following rate law for the reaction within the 3.65 to 5.5 pH range:

Kinetics and mechanism of the oxidation ofbis(2,4,6-tripyridyl-1,3,5-triazine)iron(II) bytrans-1,2-diaminocyclohexanetetraacetatomanganate(III) in acetate buffer

The rapid oxidation ofbis(2,4,6-tripyridyl-1,3,5-triazine)-iron(II), [Fe(TPTZ)₂]²⁺, bytrans-1,2-diaminocyclohexanetetraacetatomanganate(III), [Mn^III(Y)]⁻, in acetate buffers was monitored using stopped-flow spectrophotometry. The reaction is first order in the substrate and evidence was obtained for pre-complexation between the oxidant and the substrate. The reaction rate increases as the pH increases. Characterisation of the products using the radiotracers⁵⁴Mn and⁵⁹Fe indicated that [Mn^II(Y)]²⁻ and [Fe(TPTZ)₂]³⁺ are the final products. The reaction obeys the rate law:

Kinetic and equilibrium studies of the acid dissociation of the copper(II) and nickel(II) complexes of 5,7-dioxo-1,4,8,11-tetra-azacyclotetradecane

The acid catalysed dissociation of the copper(II) and nickel(II) complexes of 5,7-dioxo-1,4,8,11-tetra-azacyclo-tetradecane (dioxocyclam = LH₂) has been studied using nitric acid solutions over a range of temperatures at I = 1.0 mol dm si-³. The kinetic data for the copper complex can be fitted to the rate expression k _obs = k K ₂[H⁺]/(1 + K ₂ [H⁺] with K = 24.7s⁻¹ and K ₂ = 65dm³mol⁻¹ at 25° C. The analogous constants for the nickel(II) complex are K = ³.³s⁻¹ and K ₂ = 45dm³mol⁻¹. The acid dissociation can be rationalized in terms of the kinetic scheme

A comparative kinetic and mechanistic study of glutamic acid oxidation by acid permanganate in the absence and presence of sodium dodecyl sulphate

The kinetics and mechanism of glutamic acid (GCO₂H) oxidation by acid permanganate has been carried out in the absence and presence of sodium dodecyl sulphate (SDS). The surfactant enhances the reaction rate without changing the reaction mechanism. The overall rate expression for the reduction of Mn^VII may be written:

Conformations of fold part in isotactic polypropylene lamella with diamond lattice model

Ｉｎｔｈｅｆｉｅｌｄｏｆｐｏｌｙｍｅｒｐｈｙｓｉｃｓ,ｔｈｅｃｒｙｓｔａｌｌｉｎｅｓｔａｔｅｏｆｐｏｌｙｍｅｒｓｈａｓｌｏｎｇｂｅｅｎｏｆｉｎｔｅｒｅｓｔ.ＴｈｅｅｘｉｓｔｅｎｃｅｏｆｐｏｌｙｍｅｒｓｉｎｇｌｅｃｒｙｓｔａｌｗａｓｆｉｒｓｔｄｉｓｃｏｖｅｒｅｄｂｙＪａｃｃｏｄｉｎｅ[1]ｉｎ1955.Ｔｈｅｔｈｉｃｋｎｅｓｓｏｆｍｏｓｔｓｏｌｕｔｉｏｎｇｒｏｗｔｈｃｒｙｓｔａｌｓｉｓｆｏｕｎｄｔｏｂｅｏｆｔｈｅｏｒｄｅｒｏｆ～10ｎｍ.Ｔｈｉｓｏｂｓｅｒｖａｔｉｏｎｉｓｓｏｍｅｗｈａｔｓｕｒｐｒｉｓｉｎｇ.Ｓ…     

Kinetic studies on the dissociation of triethylenetetramine complexes of nickel(II) and copper(II) in aqueous acid media

From stopped-flow spectrophotometric studies on the kinetics of dissociation of [M(trien)]²⁺ (M=Cu^II, Ni^II) to M _aq ²⁺ and trien H ₄ ⁴⁺ in aqueous acid medium, it has been established that the reaction occurs in a complex manner conforming to the relation

Kinetics of the manganese(III)-oxalate reaction in acidic sulphate media

The kinetics of the reaction of manganese(III) with oxalic acid (OA) has been studied in H₂SO₄ solutions. Under the experimental conditions of 6 × 10^–3 <>₀ < 0.4=" mol=">^–3 and [H₂SO₄]₀ 0.2 mol dm^–3 the observed pseudo-first order rate constant k _obs follows the expression

Protonierungskonstanten der 8-Hydroxychinolinat-Ionen bei 25°C und in 1m-NaClO4

The protonation of the 8-hydroxyquinolinate ion (Ox ^?) has been studied at 25°C in 1m-NaClO₄ by the potentiometric method and the distribution between CHCl₃ and H₂O. The experimental data are explained by the following equilibria: $$\begin{array}{*{20}c} {H^ + + Ox^ - \rightleftharpoons HOx} \\ {H^ + + Ox \rightleftharpoons H_2 Ox^ + } \\ {HOx_w \rightleftharpoons HOx_{org} } \\ \end{array} \begin{array}{*{20}c} {\log k_1 = 9.42 \pm 0.08} \\ {\log k_2 = 5.46 \pm 0.10} \\ {\log \lambda = 2.40 \pm 0.10} \\ \end{array} $$      

Kinetic study of hydrogen peroxide reaction with hydroxonitrilotri(methylenephosphonato)iron(III) complex

The decomposition of hydrogen peroxide in the presence of hydroxonitrilotri(methylenephosphonato)iron(III), [Fe(NTMP)(OH)^4–], was studied in nitrate media (=0.10–0.26 M) over the 0.2–0.5 mM concentration range for the iron complex and the temperature range 26–40°C. The rate law;

Kinetics of the oxidation of [N-(2-hydroxyethyl)-ethylene-diamine-N,N′,N′-triacetato]cobalt(II) by N-bromosuccinimide

The kinetics of the oxidation of [N-(2-hydroxyethyl)-ethylene-diamine-N,N,N-triacetato] cobalt(II), [Co^II-(HEDTA)]^–, by N-bromosuccinimide, NBS, have been studied in aqueous solutions and water-methanol solvent mixtures under various conditions. The reaction stoichiometry indicates that one mole of NBS reacts with one mole of [Co^II(HEDTA)]^–. In aqueous solutions the reaction obeys the following rate law:

Reactions of alkoxy and hydroxy radicals generated photochemically from hydroperoxide molecules

In the present work as well as HRO^. radicals were generated in the photochemical interaction of 1,2-benzanthracene with -ethyl phenyl hydroperoxide /HROOH/ in C₆H₆ and CCl₄ at 304 K. radicals were trapped by C₆H₆. The main reaction of HRO^. radicals is hydrogen abstraction from the hydroperoxide group of HROOH. Although OH radicals are less selective, the hydrogen abstraction is the main process during their interaction with aromatics in contrast to reactions in aqueous solutions, where addition to the benzene ring is the rate-determining process in CCl₄:

Kinetics and mechanism of the oxidation of hydrogen peroxide by the octacyanotungstate(V) ion in alkaline aqueous media

Summary The oxidation of H₂O₂ by [W(CN)₈]^3– has been studied in aqueous media between pH 7.87 and 12.10 using both conventional and stopped-flow spectrophotometry. The reaction proceeds without generation of free radicals. The experimental overall rate law, , strongly suggests two types of mechanisms. The first pathway, characterized by the pH-dependent rate constant k _s, given by , involves the formation of [W(CN)₈· H₂O₂]^3–, [W(CN)₈· H₂O₂·W(CN)₈]^6– and [W(CN)₈· HO]^3– intermediates in rapid pre-equilibria steps, and is followed by a one-electron transfer step involving [W(CN)₈·HO]^3– (k _a) and its conjugate base [W(CN)₈·O]^4– (k _b). At 25 °C, I = 0.20 m (NaCl), the rate constant with H _a =40±6kJmol^–1 and S _a =–151±22JK^–1mol^–1; the rate constant with H _b =36±1kJmol^–1 and S _b =–136±2JK^–1mol^–1 at 25 °C, I = 0.20 m (NaCl); the acid dissociation constant of [W(CN)₈·HO]^3–, K ₅ =(5.9±1.7)×10^–10 m, with and is the first acid dissociation constant of H₂O₂. The second pathway, with rate constant, k _f, involves the formation of [W(CN)₈· HO₂]^4– and is followed by a formal two-electron redox process with [W(CN)₈]^3–. The pH-dependent rate constant, k _f, is given by . The rate constant k ₇ =23±6m ^–1 s ^–1 with and at 25°C, I = 0.20 m (NaCl).     

Mechanistic aspects of ligand substitution incis-diaquabis(bipyridine)ruthenium(II) ion by acetyl acetone

The effects of pH, temperature, acetyl acetone (acacH) concentration and substrate complex concentration on the rate of aqua ligand substitution in the title complex in aqueous medium have been studied. The following rate expression is proposed for the 5.0–6.5 pH range.

The Hydrolysis of Protactinium(V) Studied by Capillary Diffusion

The mean diffusion coefficient of ²³³Pa has been measured simultaneously with those of ²²Na and ¹⁵²Eu in 0.5 M (Na, H)ClO₄ solutions with the pH ranging from 0.3 to 13, by the open-end capillary method optimized in order to obtain reproducible and reliable D values at T = 25°C. In the case of Eu(III), the results tend to give higher ₁₃ and ₁₄ hydrolysis constants than the values generally acccepted, but these data are probably affected by the formation of polynuclear or colloidal species as soon as the hydrolysis process is involved. For Pa(V), results are in agreement with the existence of the following two equilibria (I = 0.5 M, T = 25°C):

Kinetics and mechanism of hydrolysis ofcis-bis(ethylenediamine)imidazole(salicylato)cobalt(III) ion

Summary The kinetics of aquation and base hydrolysis reactions ofcis-[(en)₂Co(imH)O₂CC₆H₄OH-o-o]²⁺ (imH = imidazole) have been investigated in a medium of 1.0 M ionic strength, In the 0,1–1,0 M [H⁺] range (60–70°) aquation proceedsvia spontaneous and acid catalysed paths . In the 0,05–1.0 M [OH^–] range (30–40°), the complex exists predominantly as the bis-deprotonated species,cis-[(en)₂Co(im)O₂CC₆H₄O-o], and the pseudo-first-order rate constant fits the relationship k_obs = k_b + k_b° [OH^–] satisfactorily. The labilizing action of coordinated imidazolate anion(im^–) on the cobalt(III)-bound salicylate is 10³ times stronger than that of imidazole. The mechanism is essentially I_d in the aquation paths and SN₁cb (Co-O bond fission) in the alkali independent and dependent paths respectively.