scholarly journals Kinetics and mechanisms of oxidation of methylamine by permanganate ion

1987 ◽  
Vol 65 (10) ◽  
pp. 2373-2379 ◽  
Author(s):  
Fernando Mata-Perez ◽  
Joaquin F. Perez-Benito
Keyword(s):  
Experimental Data ◽  
Manganese Dioxide ◽  
Rate Constants ◽  
Activation Parameters ◽  
Soluble Form ◽  
Phosphate Ions ◽  
Catalytic Mechanisms ◽  
Permanganate Ion

The oxidation of methylamine by permanganate ion in aqueous phosphate buffers is autocatalyzed by a soluble form of colloidal manganese dioxide temporarily stabilized in solution by adsorption of phosphate ions on its surface. The dependence of the rate constants of both the noncatalytic and catalytic mechanisms on the concentrations of both methylammonium and hydroxyl ions and on temperature has been determined. The activation parameters have been obtained. Mechanisms in agreement with the experimental data are proposed.

Identification of the product from the reduction of permanganate ion by trimethylamine in aqueous phosphate buffers

1985 ◽  
Vol 63 (4) ◽  
pp. 988-992 ◽  
Author(s):  
Fernando Mata-Perez ◽  
Joaquin F. Perez-Benito
Keyword(s):  
Manganese Dioxide ◽  
Potassium Permanganate ◽  
Energy Of Activation ◽  
Soluble Form ◽  
Phosphate Ions ◽  
Flocculation Process ◽  
Apparent Energy Of Activation ◽  
Permanganate Ion

The product obtained from the reduction of potassium permanganate by trimethylamine in aqueous phosphate buffers has been identified as a soluble form of colloidal manganese dioxide which is stabilized in solution by adsorption of phosphate ions on its surface. The dependence of the rate of flocculation on several experimental variables has been studied. Phosphate ions have been found to increase the solubility of the colloid by increasing the apparent energy of activation of the flocculation process. This could explain the well-known capacity of those ions for retarding the precipitation of manganese dioxide.

Kinetics and mechanism of the oxidation of L-α-amino-n-butyric acid in moderately concentrated sulfuric acid medium

2004 ◽  
Vol 82 (3) ◽  
pp. 430-436 ◽  
Author(s):  
Homayoon Bahrami ◽  
Mansour Zahedi
Keyword(s):  
Acid Medium ◽  
Butyric Acid ◽  
Rate Constants ◽  
Activation Parameters ◽  
Strong Acid ◽  
Acid Oxidation ◽  
Radical Intermediates ◽  
Sulfuric Acid Medium ◽  
Concentrated Sulfuric Acid ◽  
Permanganate Ion

The reaction kinetics of L-α-amino-n-butyric acid oxidation by permanganate ion have been investigated in moderately strong acid medium using a spectrophotometric technique. In all cases studied an autocatalytic effect, due to Mn+2 ions formed as a reaction product, was observed. Both catalytic and noncatalytic processes were determined to be first order with respect to the permanganate ion and the amino acid. The overall rate equation for this process may be written as: [Formula: see text] where k′1 and k′2 are pseudo-order rate constants for the noncatalytic and catalytic reactions, respectively. The influence of some factors such as temperature and reactant concentration on the rate constants has been studied, and the activation parameters have been calculated. Reaction mechanisms satisfying observations for both catalytic and noncatalytic routes have been presented.Key words: L-α-amino-n-butyric acid, permanganate oxidation, concentrated acidic medium, autocatalysis, free radical intermediates.

Instability of Solutions of Quaternary Ammonium Permanganates in Dichloromethane

1997 ◽  
Vol 62 (6) ◽  
pp. 849-854 ◽  
Author(s):  
Vladislav Holba ◽  
Renata Košická
Keyword(s):  
Ammonium Salt ◽  
Rate Constants ◽  
Quaternary Ammonium ◽  
Quaternary Ammonium Salt ◽  
Activation Parameters ◽  
The Stability

The paper deals with instability of solutions of quaternary ammonium permanganates, QMnO4 (Q = tetraethyl-, tetra-1-propyl-, tetra-1-butyl-, tetra-1-pentyl-, tetra-1-octyl-, and cetyltrimethylammonium), in dichloromethane and presents the rate constants and activation parameters of the reduction of permanganate. Attention was paid to the properties of colloidal Mn(IV) intermediate. The stability of the solutions depends markedly on the quaternary ammonium salt used.

scholarly journals Rate and Product Studies with 1-Adamantyl Chlorothioformate under Solvolytic Conditions

2021 ◽  
Vol 22 (14) ◽  
pp. 7394
Author(s):  
Kyoung Ho Park ◽  
Mi Hye Seong ◽  
Jin Burm Kyong ◽  
Dennis N. Kevill
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Ion Pairs ◽  
Carbonyl Sulfide ◽  
Activation Parameters ◽  
Chloride Ions ◽  
Reaction Channels ◽  
Decomposition Pathway ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

A study was carried out on the solvolysis of 1-adamantyl chlorothioformate (1-AdSCOCl, 1) in hydroxylic solvents. The rate constants of the solvolysis of 1 were well correlated using the Grunwald–Winstein equation in all of the 20 solvents (R = 0.985). The solvolyses of 1 were analyzed as the following two competing reactions: the solvolysis ionization pathway through the intermediate (1-AdSCO)+ (carboxylium ion) stabilized by the loss of chloride ions due to nucleophilic solvation and the solvolysis–decomposition pathway through the intermediate 1-Ad+Cl− ion pairs (carbocation) with the loss of carbonyl sulfide. In addition, the rate constants (kexp) for the solvolysis of 1 were separated into k1-Ad+Cl− and k1-AdSCO+Cl− through a product study and applied to the Grunwald–Winstein equation to obtain the sensitivity (m-value) to change in solvent ionizing power. For binary hydroxylic solvents, the selectivities (S) for the formation of solvolysis products were very similar to those of the 1-adamantyl derivatives discussed previously. The kinetic solvent isotope effects (KSIEs), salt effects and activation parameters for the solvolyses of 1 were also determined. These observations are compared with those previously reported for the solvolyses of 1-adamantyl chloroformate (1-AdOCOCl, 2). The reasons for change in reaction channels are discussed in terms of the gas-phase stabilities of acylium ions calculated using Gaussian 03.

The kinetics, isotope effects, and mechanism of the reaction of 2,2-di(4-nitrophenyl)-1,1,1-trifluoroethane with alkoxide bases in alcohol solvents

1985 ◽  
Vol 63 (3) ◽  
pp. 576-580 ◽  
Author(s):  
Arnold Jarczewski ◽  
Grzegorz Schroeder ◽  
Wlodzimierz Galezowski ◽  
Kenneth T. Leffek ◽  
Urszula Maciejewska
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Activation Parameters ◽  
Tert Butanol ◽  
Deuterium Isotope Effects ◽  
Alcohol Solvents ◽  
Multistep Reaction ◽  
Mechanism Of The Reaction

The reaction between 2,2-di(4-nitrophenyl)-1,1,1-trifluoroethane and the alkoxide bases ŌCH3, ŌC2H5, ŌnC4H9, ŌCH(CH3)2, and ŌC(CH3)3 in their corresponding alcohol solvents is a multistep reaction with several intermediates: 2,2-di(4-nitrophenyl)-1,1-difluoro-1-alkoxyethane (A), 2,2-di(4-nitrophenyl)-1-fluoro-1-alkoxyethene (B), 2,2-di(4-nitrophenyl)-1,1-dialkoxyethene (C), 2,2-di(4-nitrophenyl)-1,1-difluoroethene (D), and 4,4′-dinitrobenzophene (E). Rate constants and activation parameters have been measured for the appearance of the two stable products B and C. The kinetic deuterium isotope effects for the appearance of B fell in the range of kH/kD = 1 to 2 at 25 °C for the primary and secondary alkoxides, whereas kH/kD = 5.4 at 30 °C for the appearance of D with tert-butoxide. Exchange experiments showed that H/D exchange took place between the substrate and solvent to the extent of 100% with methoxide, 50% with ethoxide and isopropoxide, and 0% with tert-butoxide. It is concluded the HF elimination from the substrate follows an (ElcB)R mechanism with methoxide/methanol, changing to (ElcB)I or E2 with tert-butoxide/tert-butanol.

Mechanodestruction of Isoprene Rubber. Part 1. Process Kinetics

2021 ◽  
Vol 80 (3) ◽  
pp. 118-122
Author(s):  
V.P. Dorozhkin ◽  
◽  
E.G. Mokhnatkina ◽  
D.N. Zemsky ◽  
A.D. Valiev ◽  
...  
Keyword(s):  
Experimental Data ◽  
Molecular Mass ◽  
Rate Constants ◽  
Oxidative Destruction ◽  
Process Kinetics ◽  
Mass Fractions ◽  
Rubber Part ◽  
Kinetics Of ◽  
Selection Of ◽  
Isoprene Rubber

A method is proposed that allows us to obtain the values of the rate constants (CR) of the processes of mechanodestruction (mechanical cracking) of kм, oxidative destruction of kо, and recombination of kр macromolecules, as well as the mass fractions of the corresponding fractions of φм, φо, and φр,r involved in the plasticization process (P) of SKI-3 isoprene rubber. The method is based on the selection of the values of these parameters that correspond to the previously obtained experimental data, using the previously obtained recurrent equations and a specially developed program. The dependences of the CR on the time P at 30oC are obtained, which allows us to describe the kinetics of the processes accompanying P at this temperature, and the changes in molecular mass (MM) in this process. It is shown that constant values of CR are established at large times of P. Refined explanations of the nature of the kinetics of the CR change at P are proposed. The MM value of SKI-3 macromolecules that have not undergone destruction is calculated, depending on the time of plasticization.

The decomposition of aliphatic N-nitro amines in aqueous sulfuric acid. Bisulfate as a nucleophile

1996 ◽  
Vol 74 (10) ◽  
pp. 1774-1778 ◽  
Author(s):  
Robin A. Cox
Keyword(s):  
Sulfuric Acid ◽  
Water Molecule ◽  
Rate Constants ◽  
Activation Parameters ◽  
Standard State ◽  
Aqueous Sulfuric Acid ◽  
Alkyl Groups ◽  
Different Temperatures ◽  
State Rate ◽  
Acid Catalyzed

In aqueous sulfuric acid, aliphatic N-nitro amines decompose to N2O and alcohols. An excess acidity analysis of the observed rate constants for the reaction shows that free carbocations are not formed. The reaction is an acid-catalyzed SN2 displacement from the protonated aci-nitro tautomer, the nucleophile being a water molecule at acidities below 82–85% H2SO4, and a bisulfate ion at higher acidities. Bisulfate is the poorer nucleophile by a factor of about 1000. Twelve compounds were studied, of which results obtained for nine at several different temperatures enabled calculation of activation parameters for both nucleophiles. The reaction appears to be mainly enthalpy controlled. The intercept standard-state rate constants are well correlated by the σ* values for the alkyl groups; the slopes are negative, with a more negative value for the slower bisulfate reaction. Interestingly the m≠m* slopes also correlate with σ*, although the scatter is bad. Key words: N-nitro amines, excess acidity, bisulfate, nucleophiles, acid-catalyzed, kinetics.

[3,3] Sigmatropic Rearrangement of Some Fluorinated 1,5-Hexadienes

2002 ◽  
Vol 67 (10) ◽  
pp. 1517-1532 ◽  
Author(s):  
William R. Dolbier ◽  
Keith W. Palmer ◽  
Feng Tian ◽  
Piotr Fiedorow ◽  
Andrzej Zaganiaczyk ◽  
...  
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Transition States ◽  
Activation Parameters ◽  
Sigmatropic Rearrangement ◽  
Semiempirical Methods ◽  
Cope Rearrangement ◽  
Computational Studies ◽  
Stepwise Mechanism ◽  
Radical Intermediates

Fluorine atoms incorporated into 1,5-hexadiene molecule should influence the kinetic as well as the thermodynamic parameters of [3,3] sigmatropic rearrangement (Cope rearrangement). Within few decades is has been documented that this transformation proceeds in a concerted manner, rather than stepwise with some radical intermediates involved. Few new terminally fluorinated 1,5-hexadienes (compounds 3, 5A, 7, 9 and 5B) have been synthesized. The activation parameters of rearrangement have been determined and compared with those known for hydrocarbon analogues. While systems developing chair-like transition states (compounds 3 and 5) showed close similarity with hydrocarbon analogues (compound 1), those developing boat-like transition states (compounds 7, 9 and 5B) may proceed through radical stepwise mechanism. Computational studies of the transition states were carried out, showing that only ab initio methods (MP2 and especially DFT) can give approximate correlation with experimental data, whereas in the case of hydrocarbon analogues even simple semiempirical methods (AM1) were reliable enough to reproduce experimental results.

scholarly journals The study of phosphate ions sorption from silicon dioxide solutions obtained by using acid decomposition of nepheline

2021 ◽  
Vol 12 (2-2021) ◽  
pp. 42-47
Author(s):  
Yu. O. Velyaev ◽  
◽  
D. V. Maiorov ◽  
Keyword(s):  
Experimental Data ◽  
Silicon Dioxide ◽  
Equilibrium Constant ◽  
Municipal Wastewater ◽  
Adsorption Equilibrium ◽  
Sorption Process ◽  
Acid Decomposition ◽  
Phosphate Ion ◽  
Phosphate Ions ◽  
Adsorption Monolayer

The process of sorption of phosphate ion by silicon dioxide obtained by acid decomposition of nepheline is studied. The experimental data were processed using the Freundlich and Langmuir sorption equations, which showed that the sorption process is fairly accurately described by both equations, while the use of the Langmuir monomolecular adsorption equation is preferable in the calculations. The capacity of the adsorption monolayer of the synthesized sample relative to the РО43–-ion and the adsorption equilibrium constant are calculated. Based on the obtained data, various options for sorption treatment of municipal wastewater from РО43--ion to normalized MPC values were evaluated.

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