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.

scholarly journals The dissociation energy of the C-N bond in benzylamine

1949 ◽  
Vol 198 (1053) ◽  
pp. 285-292 ◽  
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Dissociation Energy ◽  
Heat Of Formation ◽  
Molar Ratio ◽  
Kcal Mole ◽  
First Order ◽  
First Order Kinetics ◽  
Permanent Gases ◽  
Kinetics Of

The kinetics of the thermal decomposition of benzylamine were studied by a flow method using toluene as a carrier gas. The decomposition produced NH 3 and dibenzyl in a molar ratio of 1:1, and small quantities of permanent gases consisting mainly of H 2 . Over a temperature range of 150° (650 to 800° C) the process was found to be a homogeneous gas reaction, following first-order kinetics, the rate constant being expressed by k = 6 x 10 12 exp (59,000/ RT ) sec. -1 . It was concluded, therefore, that the mechanism of the decomposition could be represented by the following equations: C 6 H 5 . CH 2 . NH 2 → C 6 H 5 . CH 2 • + NH 2 •, C 6 H 5 . CH 3 + NH 2 •→ C 6 H 5 . CH 2 • + NH 3 , 2C 6 H 5 . CH 2 •→ dibenzyl, and the experimentally determined activation energy of 59 ± 4 kcal./mole is equal to the dissociation energy of the C-N bond in benzylamine. Using the available thermochemical data we calculated on this basis the heat of formation of the NH 2 radical as 35.5 kcal./mole, in a fair agreement with the result obtained by the study of the pyrolysis of hydrazine. A review of the reactions of the NH 2 radicals is given.

Ethylene exchange in PtCl(C5H7O2)(π-C2H4)

1970 ◽  
Vol 48 (24) ◽  
pp. 3802-3806 ◽  
Author(s):  
C. E. Holloway ◽  
J. Fogelman
Keyword(s):  
Activation Energy ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Kcal Mole ◽  
First Order ◽  
First Order Kinetics ◽  
Solvent Dependence ◽  
Kinetics Of

The kinetics of exchange of free with complexed ethylene in the system PtCl(acac)(π-C2H4) have been investigated over a temperature and concentration range by proton magnetic resonance. First order kinetics are observed with respect to each component with no solvent dependence of rate. The activation energy and entropy are 2.7 kcal mole−1 and −36 cal deg−1 mole−1, respectively. A five coordinate intermediate is suggested, with complete retention of configuration at the platinum.

Nitrogen Bridged Osmium-Ruthenium Complexes

1971 ◽  
Vol 49 (2) ◽  
pp. 207-210 ◽  
Author(s):  
Clive M. Elson ◽  
J. Gulens ◽  
John A. Page
Keyword(s):  
Absorption Band ◽  
Ruthenium Complexes ◽  
Second Order ◽  
Kcal Mole ◽  
First Order ◽  
First Order Kinetics ◽  
Equilibrium Concentrations

The formation of [(H2O)(NH3)4Ru—N2—Os(NH3)5]4+ by the reaction of cis-Ru(NH3)4(H2O)22+and Os(NH3)5N22+ has been studied over the range 15–45 °C. The reaction followed second order kinetics with kt = 1.2 × 10–1 M–1 s–1 at 25.0 °C and Ea = 16.8 ± 0.1 kcal/mole. Measurement of equilibrium concentrations gave Keq = 4 × 103 M−1 at 25.0 °C.The (4+) dimer was stable but removal of the excess cis-Ru(NH3)4(H2O)22+ reactant by oxidation at −0.10 V was followed by dimer decomposition. The breakup obeyed simple first order kinetics with kr = 2.9 × 10−5 s−1 at 25.0 °C.Oxidation of the (4+) dimer at + 0.10 V gave a stable (5+) dimer. Removal of the excess Os(NH3)5N22+ reactant at + 0.30 V was followed by decomposition of the (5+) dimer giving Os(NH3)5N22+ and RuIII(NH3)4X2. The decomposition again obeyed first order kinetics with k1 = 1.5 × 10−5 s−1 at 25.0 °C. The (5+) dimer has an intervalence–transfer absorption band at 755 nm and is characterized as [X(NH3)4RuIII—N2—OsII(NH3)5]5+.The studies were carried out in an aqueous H2SO4–K2SO4 electrolyte of pH 3.3, µ = 0.30.

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.

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.

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.

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.

scholarly journals Engineering Increased Stability in the Antimicrobial Peptide Pediocin PA-1

2000 ◽  
Vol 66 (11) ◽  
pp. 4798-4802 ◽  
Author(s):  
Line Johnsen ◽  
Gunnar Fimland ◽  
Vincent Eijsink ◽  
Jon Nissen-Meyer
Keyword(s):  
Antimicrobial Peptide ◽  
Molecular Mass ◽  
Room Temperature ◽  
Bacteriocin Activity ◽  
Food Preservative ◽  
Food Grade ◽  
First Order ◽  
Methionine Residue ◽  
First Order Kinetics

ABSTRACT Pediocin PA-1 is a food grade antimicrobial peptide that has been used as a food preservative. Upon storage at 4°C or room temperature, pediocin PA-1 looses activity, and there is a concomitant 16-Da increase in the molecular mass. It is shown that the loss of activity follows first-order kinetics and that the instability can be prevented by replacing the single methionine residue (Met31) in pediocin PA-1. Replacing Met by Ala, Ile, or Leu protected the peptide from oxidation and had only minor effects on bacteriocin activity (for most indicator strains 100% activity was maintained). Replacement of Met by Asp was highly deleterious for bacteriocin activity.

scholarly journals Kinetic Modelling of Biodegradability Data of Commercial Polymers Obtained under Aerobic Composting Conditions

Eng ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 54-68
Author(s):  
Ilenia Rossetti ◽  
Francesco Conte ◽  
Gianguido Ramis
Keyword(s):  
Kinetic Data ◽  
Kinetic Modelling ◽  
Kinetic Equations ◽  
Second Order ◽  
Aerobic Biodegradation ◽  
First Order ◽  
First Order Kinetics ◽  
Plastic Materials ◽  
Partial Degradation ◽  
Commercial Polymers

Methods to treat kinetic data for the biodegradation of different plastic materials are comparatively discussed. Different samples of commercial formulates were tested for aerobic biodegradation in compost, following the standard ISO14855. Starting from the raw data, the conversion vs. time entries were elaborated using relatively simple kinetic models, such as integrated kinetic equations of zero, first and second order, through the Wilkinson model, or using a Michaelis Menten approach, which was previously reported in the literature. The results were validated against the experimental data and allowed for computation of the time for half degradation of the substrate and, by extrapolation, estimation of the final biodegradation time for all the materials tested. In particular, the Michaelis Menten approach fails in describing all the reported kinetics as well the zeroth- and second-order kinetics. The biodegradation pattern of one sample was described in detail through a simple first-order kinetics. By contrast, other substrates followed a more complex pathway, with rapid partial degradation, subsequently slowing. Therefore, a more conservative kinetic interpolation was needed. The different possible patterns are discussed, with a guide to the application of the most suitable kinetic model.

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