Utilisation de l'ortho-tolidine pour l'étude des réactions des halogénates et halogénites

1986 ◽  
Vol 64 (9) ◽  
pp. 1747-1751 ◽  
Author(s):  
Guy Schmitz ◽  
Henri Rooze
Keyword(s):  
Activation Energy ◽  
Ionic Strength ◽  
Fourth Order ◽  
Redox Reactions ◽  
Side Reactions ◽  
Acidity Constant ◽  
Acid Solutions ◽  
Complex Reaction ◽  
Rate Law ◽  
Bromic Acid

We have shown previously that ortho-tolidine greatly simplifies the kinetic study of redox reactions of chlorite by reacting with intermediate products and eliminating side reactions. The present study shows the validity of the method in the case of bromate reactions. For the bromate–bromide reaction it gives the classical fourth-order rate law with k = 1.54 M−3 s−1 in perchloric acid solutions at 25 °C and 1 M ionic strength, and an acidity constant of bromic acid of 2.9. This method is then used to study the reaction between bromate and chlorite, a complex reaction in the absence of ortho-tolidine. The rate law is[Formula: see text]with k = 0.83 + 0.76 [H+] in the same conditions. If [H+] = 0.1 M the apparent activation energy is 47.4 kJ/mol.

Kinetics of Oxidation of Ferrocyanide by lodate Ion

1974 ◽  
Vol 52 (11) ◽  
pp. 2001-2004 ◽  
Author(s):  
Y. Sulfab ◽  
Hamid A. Elfaki
Keyword(s):  
Activation Energy ◽  
Ionic Strength ◽  
Formation Constant ◽  
Kinetics Of Oxidation ◽  
Rate Law ◽  
Ph Range ◽  
Kinetics Of ◽  
Rate Determining Steps

In the presence of vast excess of ferrocyanide, over the pH range 1.76–2.65, the reaction between iodate and ferrocyanide ions follows the rate law[Formula: see text]where ka and kb have values of 1.97 × 103 M−2 min−1 and 4.08 × 105 M−3 min−1, respectively, at an ionic strength of 1.18 M and a temperature of 25.0 ± 0.1 °C. K1 is the formation constant of monoprotonated ferrocyanide. The "overall activation energy" of the reaction was found to be 15.8 kcal/mol. Rate-determining steps consistent with the kinetics have been proposed.

Mécanisme des réactions du chlorite et du dioxyde de chlore. 2. Cinétique des réactions du chlorite en présence d'ortho-tolidine

1984 ◽  
Vol 62 (11) ◽  
pp. 2231-2234 ◽  
Author(s):  
Guy Schmitz ◽  
Henri Rooze
Keyword(s):  
Ionic Strength ◽  
Chloride Ions ◽  
Elementary Reaction ◽  
Side Reactions ◽  
Rate Law ◽  
Intermediate Products

With added ortho-tolidine (NH2RNH2) in order to eliminate complicating side reactions of the intermediate products of the disproportionation of chlorite, the stoichiometry is HClO2 + 2NH2RNH2 → Cl− + H+ + 2NHRNH + 2H2O. No chlorate is formed. The rate law, in the absence of chloride ions, is[Formula: see text]k = 269 M−1 s−1 at 25 °C and 1 M ionic strength. Without added iron, the observed rate is only due to the small amount of iron always present as an impurity in the reactants. Thus the reaction [Formula: see text] is not an elementary reaction.

Mécanisme des réactions du chlorite et du dioxyde de chlore. 3. La dismutation du chlorite

1985 ◽  
Vol 63 (4) ◽  
pp. 975-980 ◽  
Author(s):  
Guy Schmitz ◽  
Henri Rooze
Keyword(s):  
Ionic Strength ◽  
Order Reaction ◽  
Second Order ◽  
Acid Solutions ◽  
Chain Mechanism ◽  
Second Order Reaction ◽  
Radical Chain ◽  
Rate Law ◽  
The Third ◽  
Reaction Proceeds

The disproportionation of chlorite was studied in 0.01 to 1 M perchloric acid solutions at 25 °C and an ionic strength of 1 M. The results suggest at least three reaction paths. The first is catalysed by Cl− ions, the second gives a second-order rate law, and the third is catalysed by iron. Its rate law is[Formula: see text]This can be interpreted by the reversible reaction [Formula: see text] followed by two rate-determining reactions Fe2+ + HClO2 → products, [Formula: see text] From this study and the former, made with added ortho-tolidine, we conclude that the second-order reaction proceeds by a radical chain mechanism.

Mechanisms of Plutonium Redox Reactions in Nitric Acid Solutions

2020 ◽  
Vol 59 (10) ◽  
pp. 6826-6838
Author(s):  
Sayandev Chatterjee ◽  
James M. Peterson ◽  
Amanda J. Casella ◽  
Tatiana G. Levitskaia ◽  
Samuel A. Bryan
Keyword(s):  
Nitric Acid ◽  
Redox Reactions ◽  
Acid Solutions ◽  
Nitric Acid Solutions

Kinetics of the addition of acids to olefins with and without boron fluoride catalysis

1967 ◽  
Vol 45 (1) ◽  
pp. 11-16 ◽  
Author(s):  
G. A. Latrèmouille ◽  
A. M. Eastham
Keyword(s):  
Activation Energy ◽  
Acetic Acid ◽  
Apparent Activation Energy ◽  
Trifluoroacetic Acid ◽  
Similar Rate ◽  
Ethylene Dichloride ◽  
Kcal Mole ◽  
Rate Law ◽  
Boron Fluoride ◽  
Kinetics Of

Isobutene reacts readily with excess trifluoroacetic acid in ethylene dichloride solution at ordinary temperatures to give t-butyl trifluoroacetate. The rate of the reaction is given, within the range of the experiments, by the expression d[ester]/dt = k[acid]2[olefin], and the apparent activation energy is about 6 kcal/mole. The rate of addition is markedly dependent on the strength of the reacting acid and is drastically reduced in the presence of mildly basic materials, such as dioxane. The boron fluoride catalyzed addition of acetic acid to 2-butene can be considered to follow a similar rate law, i.e. d[ester]/dt = k[acid·BF3]2[olefin], but only if some assumptions are made about the position of the equilibrium [Formula: see text]since only the 1:1 complex is reactive.

scholarly journals On the catalytic dehydrogenation of naphthenes I. Kinetic study

1947 ◽  
Vol 190 (1022) ◽  
pp. 289-308 ◽  
Keyword(s):  
Activation Energy ◽  
Main Reaction ◽  
Ethyl Benzene ◽  
Slow Step ◽  
Side Reactions ◽  
Catalytic Dehydrogenation ◽  
Hydrogen Atoms ◽  
Stationary Concentration ◽  
Methyl Cyclohexane ◽  
Kinetics Of

The kinetics of the dehydrogenation of naphthenes over a chromium oxide supported on alumina catalyst at temperatures of 400° C and above has been investigated. Cyclohexene has been detected and estimated in the products from cyclohexane, and it has been shown that side reactions producing olefine other than cyclohexene proceed at only 0.01 of the speed of the main reaction at 450° C. If the contact time is sufficiently long a stationary concentration of olefine is established. The linear nature of the plot of the reciprocal of the rate against the reciprocal of the pressure for cyclohexane and methyl cyclohexane has been demonstrated experimentally for the stationary state conditions, while the intercepts and slopes have been identified with functions of the rate constants. As a result of the study of the rate of dehydrogenation of cyclohexene it is concluded that the loss of the first pair of hydrogen atoms from cyclohexane is the slow step in the reaction. An activation energy of 36 kcal./g. mol. has been obtained for this step. The variation of the stationary olefine con­centration with temperatures indicates that for cyclohexane and methyl cyclohexane the loss of the first pair of hydrogen atoms is the step with the highest activation energy. The variation of rate with pressure and the behaviour when nitrogen and benzene are mixed with the reactants all prove that benzene and hydrogen act mainly as diluents. Evidence is presented from the failure to attain thermodynamic equilibrium between ethyl benzene, styrene and hydrogen during the dehydrogenation of ethyl cyclohexane for a stepwise mechanism in which a large proportion of the molecules evaporate from the surface after the loss of the first pair of hydrogen atoms.

Oxidation of acetylferrocene and 1,1'-diacetylferrocene with cerium(IV) sulphate in sulphuric acid medium

1979 ◽  
Vol 44 (4) ◽  
pp. 1060-1069 ◽  
Author(s):  
Jaroslav Holeček ◽  
Karel Handlíř ◽  
Jiří Klikorka
Keyword(s):  
Acid Medium ◽  
Sulphuric Acid ◽  
Rate Constants ◽  
Redox Reactions ◽  
Acid Solutions ◽  
Oxidizing Agent ◽  
Ferrocene Derivatives ◽  
Kinetic Measurements ◽  
Complete Destruction ◽  
Sulphuric Acid Medium

Oxidation of acetylferrocene and 1,1'-diacetylferrocene with cerium(IV) sulphate has been studied in aqueous sulphuric acid solutions having the overall acidity H0 = +1 to -2. The first step in oxidation of the both ferrocene derivatives consists in a fast one-electron oxidation giving the corresponding unstable ferricenium cations. Their disappearance from the solution is connected with destruction of the sandwich molecule and further redox reactions. Complete destruction of acetylferrocene necessitates two equivalents of the oxidizing agent, the same reaction of 1,1'-diacetylferrocene proceeds by action of three equivalents of the oxidizing agent. On the basis of detailed kinetic measurements mechanism of the oxidation and destruction of the both derivatives has been suggested, and rate constants of decomposition of the sandwich molecules have been determined.

The reaction between peroxomonosulphuric acid and cerium(IV) in dilute sulphuric acid solutions

1970 ◽  
Vol 23 (4) ◽  
pp. 641 ◽  
Author(s):  
WHO Billing ◽  
GJ Bridgart ◽  
IR Wilson
Keyword(s):  
Hydrogen Peroxide ◽  
Sulphuric Acid ◽  
Acid Solutions ◽  
Radical Chain ◽  
Rate Law ◽  
Early Stages

The reaction of cerium(1V) with peroxomonosulphuric acid in aqueous sulphuric acid has been shown to involve a short radical chain. Rates of reaction of cerium(1V) have been measured in dilute sulphuric acid solutions. A substantial difference was found between the apparent rate law in the early stages of reaction and that observed later. This is not due to the presence of hydrogen peroxide in the peroxomonosulphate solutions. A tentative mechanism is proposed.

SOME OBSERVATIONS ON CYANIC ACID AND CYANATES

1955 ◽  
Vol 33 (2) ◽  
pp. 426-440 ◽  
Author(s):  
M. W. Lister
Keyword(s):  
Activation Energy ◽  
Ionic Strength ◽  
Rate Constant ◽  
Ionization Constant ◽  
Side Reaction ◽  
Cyanic Acid ◽  
First Order ◽  
Second Stage ◽  
Carbonate Concentration ◽  
Considerable Range

Various reactions of cyanic acid and the cyanate ion have been examined. Cyanic acid, in the presence of added hydrochloric or nitric acid, decomposes quantitatively according to the equation: HNCO + H3O+ → CO2 + NH4+. The rate constant for this reaction was measured over a range of temperature and ionic strength, and was found to be 0.86 mole liter−1 min.−1 at unit ionic strength and 1.5 °C. The activation energy is [Formula: see text] The effect of ionic strength on the reaction with hydrochloric acid closely parallels that on the activity coefficients of the acid itself. Without added acid cyanic acid decomposes by a first order reaction: HNCO + 2H2O → NH4HCO3, followed by a rapid second stage: NH4HCO3 + HNCO → NH4NCO + H2CO3. This reaction has a rate constant of 0.011 min.−1 at 0 °C. and an activation energy of 16 kcal. There is also a few per cent of some side reaction. Cyanate ions in alkaline solution decompose thus: OCN− + 2H2O → NH4+ + CO3−−. This reaction was examined over a range of temperature and ionic strength: it is first order with k = 3.0 × 10−3 min.−1at 100 °C. (0.3 ionic strength) and [Formula: see text] activation energy. The rate is somewhat dependent on hydroxide concentration, when this is fairly low. The reaction is catalyzed by carbonate, but not by a number of other anions that were examined. The rate of the catalyzed reaction is proportional to the carbonate concentration, but independent of cyanate, at least over a considerable range. The ionization constant of cyanic acid has been measured by a method that avoids errors from hydrolysis; the value obtained was 2.0 × 10−4. The oxidation of cyanate by hypochlorite and by chlorine was examined more briefly.

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