Octahedral cobalt(III) complexes in dipolar aprotic solvents. I. The substitution of thiocyanate into the cis-Chlorodimethylsulphoxidobisethylenediaminecobalt(III) ion in anhydrous dimethylsulphoxide and NN-dimethylformamide

1965 ◽  
Vol 18 (4) ◽  
pp. 453 ◽  
Author(s):  
LF Chin ◽  
WA Millen ◽  
DW Watts
Keyword(s):  
Activation Energy ◽  
Ion Pair ◽  
Second Order ◽  
Aprotic Solvents ◽  
Kcal Mole ◽  
Dissociative Mechanism ◽  
Thiocyanate Ion ◽  
First Order ◽  
Rate Determining Step ◽  
Dipolar Aprotic Solvents

The substitution of thiocyanate ion into the cis-chlorodimethylsulphoxidobisethylenediaminecobalt(III) ion, cis-(Coen2(DMSO)Cl)2+, has been studied in the solvents dimethylsulphoxide (DMSO) and NN-dimethylformamide (DMF). In DMSO the reaction shows second-order characteristics which are accounted for by an ion-pair dissociative mechanism (SNIIP). The activation energy is 30.1 kcal mole-1. In DMF the entry is first-order, the rate determining step being solvolysis to the intermediate cis-(Coen2(DMF)Cl)2+ which has been isolated as the nitrate. In high thiocyanate concentrations the rate shows some thiocyanate dependence due to the competition of ion-paired thiocyanate with the DMF solvent for coordination following the DMSO dissociation. The activation energy for this substitution is 17.5 kcal mole-1.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. V. The substitution of chloride and thiocyanate into the cis-chlorodimethylformamidebisethylenediaminecobalt(III) ion in anhydrous NN-dimethylformamide

1966 ◽  
Vol 19 (6) ◽  
pp. 949 ◽  
Author(s):  
IR Lantzke ◽  
DW Watts
Keyword(s):  
Chloride Ion ◽  
Ion Pair ◽  
Kinetics And Mechanism ◽  
Aprotic Solvents ◽  
Dissociative Mechanism ◽  
Thiocyanate Ion ◽  
Dipolar Aprotic Solvents ◽  
Chloride Concentrations

The kinetics and mechanism of the substitution of chloride ion and thiocyanate ion into the cis-chlorodimethylformamidebisethylenediaminecobalt(111) ion, cis-[CoCl(DMF) en2]2+, have been studied in ,NN-dimethylformamide (DMF). The chloride entry shows mixed kinetics which are accounted for by two paths, a slow ion pair dissociation, and a fast bimolecular attack of chloride on an ion pair. The steric course of the reaction, which is chloride dependent, shows that the ion pair dissociative mechanism is more important at low chloride concentrations. The thiocyanate entry shows similar characteristics. Thiocyanate enters faster than chloride in the bimolecular path, but in the ion pair dissociative path, which is significant at lower anion concentration, both chloride and thiocyanate enter at the same rate.

Nucleophilic decomposition of α-disulfones

1969 ◽  
Vol 47 (6) ◽  
pp. 873-877 ◽  
Author(s):  
Paul Allen Jr. ◽  
Patrick J. Conway
Keyword(s):  
Activation Energy ◽  
Order Reaction ◽  
Second Order ◽  
Hammett Equation ◽  
Second Order Reaction ◽  
Kcal Mole ◽  
Arrhenius Activation Energy ◽  
Hydroxide Ion ◽  
First Order ◽  
Sulfur Bond

The sulfur–sulfur bond of α-disulfones is attacked by hydroxide ion in alcohol to yield sulfinate and sulfonate ion by a second-order reaction, first order in each of the reactants. With aromatic disulfones the ρ value of the Hammett equation is 0.2. The Arrhenius activation energy of the reaction of p-tolyl disulfone is 7.95 kcal/mole.

The kinetics of formation of ruthenium(II) nitrogen complexes

1970 ◽  
Vol 48 (11) ◽  
pp. 1639-1644 ◽  
Author(s):  
Clive M. Elson ◽  
I. J. Itzkovitch ◽  
John A. Page
Keyword(s):  
Activation Energy ◽  
Order Rate Constant ◽  
Second Order ◽  
Kcal Mole ◽  
Potential Reduction ◽  
First Order ◽  
Kinetics Of Formation ◽  
Controlled Potential ◽  
Kinetics Of ◽  
Electrolyte Ph

The formation of nitrogen monomers by the reaction of Ru(NH3)5(H2O)2+ and cis-Ru(NH3)4(H2O)22+ with N2 has been shown to be first order in N2 and second order overall. The formation of bridging N2 dimers by the reaction of the ruthenium(II) pentaammine and tetraammine with the monomers has been shown to be second order overall.The reactions were studied in a H2SO4–K2SO4 electrolyte pH 3.3, μ = 0.30. The ruthenium(II) species were prepared by controlled potential reduction of known ruthenium(III) species at −0.50 V at a Hg cathode. The reactions of the reduced species with N2 or the monomers were followed spectrophotometrically.The second order rate constant at 25 °C and the activation energy for the substrate Ru(NH3)5(H2O)2+ with the respective nucleophiles are: N2, 8.0 × 10−2 M−1 s−1, 22.0 ± 0.1 kcal/mole; Ru(NH3)5N22+, 3.6 × 10−2 M−1 s−1, 19.9 ± 0.5 kcal/mole; Ru(NH3)4(H2O)N22+, 2.7 × 10−2 M−1 s−1, 20.4 ± 0.8 kcal/mole. For the substrate cis-Ru(NH3)4(H2O)22+ the values are: N2, 1.0 × 10−1 M−1 s−1, 20.4 ± 0.2 kcal/mole; Ru(NH3)5N22+, 6.8 × 10−2 M−1 s−1, 18.2 ± 0.1 kcal/mole; Ru(NH3)4(H2O)N22+, 7.2 × 10−2 M −1 s−1, 17.1 ± 0.2 kcal/mole.

Vulcanization of Elastomers. 22. Thermal Vulcanization of Synthetic Rubbers. I

1959 ◽  
Vol 32 (4) ◽  
pp. 962-975
Author(s):  
Walter Scheele ◽  
Hans Dieter Stemmer
Keyword(s):  
Activation Energy ◽  
Second Order ◽  
Crosslinking Reaction ◽  
Molecular Fragments ◽  
Kcal Mole ◽  
First Order ◽  
Disulfide Content ◽  
Kinetics Of ◽  
Stable Combination ◽  
Limiting Value

Abstract In this work, the kinetics of the thermal vulcanization of Perbunan were studied with and without additives. The following results were obtained : 1. The pure thermal vulcanization of Perbunan is a very slow process which obeys a second order rate law. A limiting value of the crosslinking (reciprocal limit of equilibrium swelling) is reached, which limit is independent of the temperature. The activation energy is 23.3 kcal/mole. 2. The thermal vulcanization can be inhibited by hydroquinone but not by benzoquinone. 3. The thermal vulcanization of Perbunan can be considerably accelerated by MBTS, and other materials, and the reaction also follows a second order course. The activation starts suddenly after the expiration of an induction period, which decreases with increase in temperature. The activation energy is about 27 kcal/mole. 4. In a thermal vulcanization accelerated with MBTS, a portion of the MBTS is changed over into MBT ; the amount changed is independent of temperature. Perbunan takes up MBTS in the form of molecular fragments, in stable combination. 5. The reduction in MBTS (which falls to zero) and the increase in MBT follow a first order reaction and have the same activation energy which is also identical with the energy of activation of the accelerated crosslinking. The formation of MBT is the slower of the two reactions. 6. The rate constants for the decrease in MBTS and for the increase in MBT are independent of the starting amount of MBTS, and hence we consider that this is a unimolecular process (homolysis). 7. The rate constant for the second order crosslinking reaction increases with the square root of the initial benzothiazolyl disulfide content. 8. It is indicated that the above data must be explained, with the aid of experience in the realm of polymerization kinetics. The investigations are being continued.

THE CHEMISORPTION OF NITROGEN ON POLYCRYSTALLIN TUNGSTEN WIRES

1965 ◽  
Vol 43 (4) ◽  
pp. 532-546 ◽  
Author(s):  
L. J. Rigby
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Second Order ◽  
Mass Spectrometric ◽  
Kcal Mole ◽  
First Order ◽  
First Order Kinetics ◽  
Α Phase ◽  
Polycrystalline Tungsten ◽  
Mass Spectrometric Evidence

Desorption spectra have been obtained for successively increasing amounts of nitrogen adsorbed on three polycrystalline tungsten wires at room temperature. Two β phases were desorbed, β1 with first-order kinetics and an activation energy of 73 kcal/mole and β2with second-order kinetics and an activation energy of 75 kcal/mole. Surface impurities such as carbon or thorium reduced the size of the β1 phase. Mass spectrometric evidence showed that the small α phase was adsorbed as molecules, and the β1 and β2 phases were adsorbed as atoms.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. II. Association between cis- and trans-dichlorobisethylenediamine cobalt(III) cations,[Co en2 Cl2]+, and chloride and bromide ions in the solvents NN-dimethylformamide, dimethyl sulphoxide, and LVN-dimethylacetamide

1966 ◽  
Vol 19 (1) ◽  
pp. 43 ◽  
Author(s):  
WA Millen ◽  
DW Watts
Keyword(s):  
Spectrophotometric Method ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Dimethyl Sulphoxide ◽  
Aprotic Solvents ◽  
Ion Association Constants ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

Ion association constants at 30� have been determined for the cis-[Co en, Cl2]+Cl- ion pair in NN-dimethylformamide (DMF), NN-dimethylacetamide (DMA), and at 20.0�, 25.0�, and 30.0� in dimethyl sulphoxide (DMSO), by a spectrophotometric method. Association constants for the cis-[Co en2 Cl2]+Br- and the trans- [Co en2 Cl2]+Cl- ion pairs have also been determined in DMF at 30�.

Aromatic oxidation by cobaltic acetate in acetic acid

1969 ◽  
Vol 47 (3) ◽  
pp. 387-392 ◽  
Author(s):  
Koichiro Sakota ◽  
Yoshio Kamiya ◽  
Nobuto Ohta
Keyword(s):  
Activation Energy ◽  
Electron Transfer ◽  
Acetic Acid ◽  
Bond Energy ◽  
Hydrogen Abstraction ◽  
Steric Factor ◽  
Benzyl Acetate ◽  
Kcal Mole ◽  
First Order ◽  
Reversible Electron Transfer

A detailed kinetic study of oxidation of toluene and its derivatives by cobaltic acetate in 95 vol% acetic acid is reported. The reaction was found to be profoundly affected by a steric factor and rather insensitive to the C—H bond energy. The order of reactivities of various alkylbenzenes is quite reversal to that of hydrogen abstraction reactions. The reaction was of first-order with respect to toluene, of second-order with respect to cobaltic ion and of inverse first-order with respect to cobaltous ion. The oxidation by cobaltic ion seems to proceed via an initial reversible electron transfer from toluene to cobaltic ion, yielding [Formula: see text] which is oxidized into benzyl acetate by another cobaltic ion. The apparent activation energy for toluene was found to be 25.3 kcal mole−1, and the same activation energy was found for ethylbenzene, cumene, diphenylmethane, and triphenylmethane.

The Vulcanization of Elastomers. XI. The Vulcanization of Natural Rubber with Sulfur in the Presence of Mercaptobenzothiazole. I

1957 ◽  
Vol 30 (3) ◽  
pp. 911-927 ◽  
Author(s):  
Otto Lorenz ◽  
Elisabeth Echte
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Natural Rubber ◽  
Kinetic Analysis ◽  
Rate Constants ◽  
Network Formation ◽  
Zinc Salt ◽  
Kcal Mole ◽  
Minimum Quantity ◽  
First Order

Abstract 1. The decrease of free sulfur occurs according to the first order law during the vulcanization of natural rubber accelerated by mercaptobenzothiazole in the presence of zinc oxide. The activating energy for this reaction amounts to 30.5 kcal./mole. 2. If zinc benzothiazolylmercaptide is used as an accelerator, one obtains the same rate constants for the sulfur decrease as in the presence of mercaptobenzothiazole. These seem to be equivalent as regards their effectiveness of acceleration. 3. A kinetic analysis of the reciprocal swelling, which represents a measure of network formation, indicates that the reaction is first order. Sulfur decrease and reciprocal swelling prove to be equal processes as regards rate. This is true where vulcanization is accelerated with mercaptobenzothiazole or with the zinc salt. 4. During vulcanization there occurs a decrease of accelerator concentration. This is dependent upon the temperature and is tied in with the combination sulfur with rubber. 5. If the quantity of the accelerator added is changed, the rate constants for sulfur decrease and for reciprocal swelling do not change, provided that a minimum quantity of accelerator is present. 6. In vulcanization accelerated with zinc benzothiazolylmercaptide, zinc oxide being absent, sulfur decrease again occurs according to the first order law but considerably faster, without thereby changing the activation energy. These investigations are being continued and the results will be discussed in detail in relation to other published contributions in this field.

scholarly journals Pyrolysis of phenylmercaptoacetic acid

1968 ◽  
Vol 46 (2) ◽  
pp. 191-197 ◽  
Author(s):  
A. T. C. H. Tan ◽  
A. H. Sehon
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Carbon Monoxide ◽  
Acetic Acid ◽  
Rate Constant ◽  
Order Reaction ◽  
First Order Reaction ◽  
Kcal Mole ◽  
Dissociation Process ◽  
First Order

The pyrolysis of phenylmercaptoacetic acid was investigated by the toluene-carrier technique over the temperature range 760–835 °K. The main products of the decomposition were phenyl mercaptan, carbon dioxide, acetic acid, phenyl methyl sulfide, carbon monoxide, and dibenzyl.The overall decomposition was a first-order reaction with respect to phenylmercaptoacetic acid and could be represented by the two parallel steps:[Formula: see text]Reaction [1] was shown to be a homogeneous first-order dissociation process, and its rate constant was represented by the expression[Formula: see text]The activation energy of this reaction, i.e. 58 kcal/mole, was identified with D(C6H5S—CH2COOH).

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