Detailed kinetics of tetrafluoroethene ozonolysis

2018 ◽  
Vol 20 (44) ◽  
pp. 28059-28067 ◽  
Author(s):  
Tam V.-T. Mai ◽  
Minh v. Duong ◽  
Hieu T. Nguyen ◽  
Lam K. Huynh
Keyword(s):  
Experimental Data ◽  
Reaction Mechanism ◽  
Kinetic Analysis ◽  
Rate Constants ◽  
Rate Model ◽  
Rate Determining Step ◽  
Calculated Rate ◽  
Detailed Kinetics ◽  
Kinetics Of

The reaction mechanism was explored at the CCSD(T)/CBS//B3LYP/aug-cc-pVTZ level. Detailed kinetic analysis was firstly carried out using an ME/RRKM rate model with the inclusion of anharmonic and tunneling treatments. 1,3-Cycloaddition is found to be the rate-determining step. Calculated rate constants confirm the latest experimental data.

The kinetics of dehydroxylation of kaolinite

Clay Minerals ◽  
1987 ◽  
Vol 22 (4) ◽  
pp. 447-456 ◽  
Author(s):  
S. A. T. Redfern
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Kinetic Analysis ◽  
Rate Constants ◽  
Avrami Equation ◽  
Isothermal Thermogravimetry ◽  
Temperature Range ◽  
Homogeneous Models ◽  
Kinetics Of ◽  
Fraction Method

AbstractThe dehydroxylation of kaolinite has been investigated by isothermal thermogravimetry. Kinetic analysis using the Avrami equation shows that a combination of atomic mechanisms operates throughout the temperature range 734 K to 890 K. An empirical activation energy of 222 kJ mol-1 was calculated from the Arrhenius relationship using rate constants based on diffusion and homogeneous models. The activation energy (Ea) was calculated for a series of degrees of dehydroxylation by the time to a given fraction method, showing an increase in Ea during the early stages of the reaction. The isothermal plots indicate that OH is retained in the final stages of the reaction. The observations are explained in terms of a reaction mechanism in which kaolinite grains dehydroxylate from the edges inwards, parallel to (001).

The kinetics of partial processes in the oxidation of ascorbic acid catalyzed by vanadyl tetrasulphophthalocyanine

1982 ◽  
Vol 47 (3) ◽  
pp. 744-754 ◽  
Author(s):  
Dana M. Wagnerová ◽  
Jaroslav Votruba ◽  
Jürgen Blanck ◽  
Josef Vepřek-Šiška
Keyword(s):  
Experimental Data ◽  
Ascorbic Acid ◽  
Reaction Mechanism ◽  
Rate Constants ◽  
Stopped Flow ◽  
Adaptive Identification ◽  
Flow Method ◽  
Acid Catalyzed ◽  
Kinetics Of

The rapid partial reactions of the oxidation of ascorbic acid by dioxygen with vanadyl tetrasulphophthalocyanine as a catalyst were studied by the stopped-flow method. The experimental data were treated on a computer and compared with the kinetic implications resulting from the proposed mechanism. Application of the adaptive identification method led to quantitative solution of the mechanism, i.e. determination of the values of all the isolated rate constants of the reaction mechanism.

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.

Detailed kinetics of hydrogen abstraction from trans-decalin by OH radicals: the role of hindered internal rotation treatment

2020 ◽  
Vol 22 (44) ◽  
pp. 25740-25746
Author(s):  
Tam V.-T. Mai ◽  
Lam K. Huynh
Keyword(s):  
Master Equation ◽  
Hydrogen Abstraction ◽  
Kinetic Mechanism ◽  
Oh Radicals ◽  
Rate Model ◽  
Wide Range ◽  
Detailed Kinetics ◽  
Kinetics Of ◽  
Detailed Kinetic Mechanism

The detailed kinetic mechanism of the trans-decalin + OH reaction is firstly investigated for a wide range of conditions (T = 200–2000 K & P = 0.76–76000 Torr) using the M06-2X/aug-cc-pVTZ level and stochastic RRKM-based Master equation rate model.

Untersuchung der alkalischen Hydrolyse des Benzoesäurebenzylesters in Wasser-Äthanol 1 : 1 / Study of the Basic Hydrolysis of Benzyl Benzoate in Water-Ethyl Alcohol 1:1

1974 ◽  
Vol 29 (11) ◽  
pp. 1697-1698 ◽  
Author(s):  
F. Mansilla ◽  
P. Martinez ◽  
J. Sancho
Keyword(s):  
Experimental Data ◽  
Reaction Mechanism ◽  
Order Rate Constant ◽  
Benzyl Benzoate ◽  
Conductometric Method ◽  
Alcohol Medium ◽  
Basic Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Water Alcohol

By using a conductometric method, the kinetics of the basic hydrolysis of benzyl benzoate in water-alcohol medium has been investigated. The second order rate constant follows the equation K = A exp {-E/RT} with A = 1.35·1010 l mol-1 min-1 and E = 14.5 kcal mol-1. A reaction mechanism is postulated, which is consistent with the experimental data.

Kinetics of iron(III) hydrolysis and precipitation in aqueous glycine solutions assessed by voltammetry

2009 ◽  
Vol 74 (10) ◽  
pp. 1531-1542 ◽  
Author(s):  
Vlado Cuculić ◽  
Ivanka Pižeta
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Rate Constants ◽  
Glycine Concentration ◽  
First Order ◽  
Mercury Drop Electrode ◽  
Calculated Rate ◽  
Cathodic Voltammetry ◽  
Kinetics Of ◽  
Voltammetric Measurements

The kinetics of iron(III) hydrolysis and precipitation in aqueous glycine solutions were studied by cathodic voltammetry with a mercury drop electrode. The kinetics was controlled by changing ionic strength (I), pH and glycine concentration. Voltammetric measurements clearly showed formation and dissociation of a soluble Fe(III)–glycine complex, formation of iron(III) hydroxide and its precipitation. The rate constants of iron(III) hydroxide precipitation were assessed. The precipitation is first-order with respect to dissolved inorganic iron(III). The calculated rate constants of iron(III) precipitation varied from 0.18 × 10–5 s–1 (at 0.2 M total glycine, pH 7.30, I = 0.6 mol dm–3) to 2.22 × 10–3 s–1 (at 0.1 M total glycine, pH 7.30, I = 0.2 mol dm–3). At 0.5 M total glycine and I = 0.6 mol dm–3, the iron(III) precipitation was not observed.

scholarly journals Kinetics of the non-specific calcium leak from non-mitochondrial calcium stores in permeabilized A7r5 cells

1996 ◽  
Vol 317 (3) ◽  
pp. 849-853 ◽  
Author(s):  
Ludwig MISSIAEN ◽  
Humbert DE SMEDT ◽  
Jan B. PARYS ◽  
Luc RAEYMAEKERS ◽  
Guy DROOGMANS ◽  
...  
Keyword(s):  
Rate Constants ◽  
Initial Phase ◽  
Mitochondrial Calcium ◽  
Calcium Stores ◽  
Spontaneous Release ◽  
A7r5 Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Detailed Kinetics ◽  
Kinetics Of ◽  
Single Exponential

We have investigated the detailed kinetics of the passive Ca2+ leak from non-mitochondrial Ca2+ stores in permeabilized A7r5 cells. The decrease in the content of stored Ca2+ in the presence of 2 μM thapsigargin deviated from a single-exponential curve in the initial phase of the efflux. The deviation persisted after correcting this efflux for passively bound Ca2+. The non-single-exponential nature of the spontaneous release also occurred when the initial store Ca2+ content was reduced to 40% of its original value by pretreatment with 200 nM inositol 1,4,5-trisphosphate (InsP3). The passive Ca2+ leak could be modelled by two exponential curves with discrete rate constants of 0.06 min-1 and 0.98 min-1, and not by any other type of non-exponential decay. We concluded that individual store units are heterogeneous with respect to their passive Ca2+ permeability. This non-exponential nature of the passive Ca2+ release is unrelated to the non-single-exponential InsP3-induced Ca2+ release.

The retroaldol reaction of 3-methyl-2-butenal

1983 ◽  
Vol 61 (1) ◽  
pp. 171-178 ◽  
Author(s):  
J. Peter Guthrie ◽  
Brian A. Dawson
Keyword(s):  
Sodium Hydroxide ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Aqueous Sodium Hydroxide ◽  
Initial Increase ◽  
Aqueous Sodium ◽  
Rate Determining Step ◽  
Kinetics Of

In aqueous sodium hydroxide solutions at 25 °C, 3-methyl-2-butenal, 1c, undergoes retroaldol cleavage to acetone and acetaldehyde. The kinetics of the retroaldol reaction were followed spectrophotometrically at 242 nm and showed simple first order behavior. When 3-methyl-3-hydroxybutanal, 2c, was added to aqueous sodium hydroxide solutions at 25 °C, there was an initial increase in absorbance at 242 nm, attributed to formation of 1c, followed by a 20-fold slower decrease; the rate of the slow decrease matches the rate of disappearance of 1c under the same conditions. Analysis of the kinetics allows determination of the three rate constants needed to describe the system: khyd = 0.00342; kdehyd = 0.00832; kretro = 0.0564; all M−1 s−1. The equilibrium constant for enone hydration is 0.41. Rate constants for the analogous reactions for acrolein and crotonaldehyde could be obtained from the literature. There is a reasonable rate–equilibrium correlation for the retroaldol step. For the enone hydration step, rate and equilibrium constants respond differently to replacement of hydrogen by methyl. It is proposed that this results from release of strain after the rate-determining step by rotation about a single bond; this decrease in strain is reflected in the equilibrium constant but not in the rate constant.

Vulcanization of Elastomers. 40. Vulcanization of Natural Rubber and Synthetic Rubber with Sulfur in Presence of Sulfenamides. III

1965 ◽  
Vol 38 (1) ◽  
pp. 189-203 ◽  
Author(s):  
W. Scheele ◽  
J. Helberg
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Natural Rubber ◽  
Rate Constants ◽  
Sulfur Concentration ◽  
Kcal Mole ◽  
Synthetic Rubber ◽  
Chemical Constitution ◽  
Induction Times ◽  
Kinetics Of

Abstract Vulcanization of natural rubber with sulfur was studied in presence of six sulfenamides, to determine the effect of the chemical constitution of the sulfenamide on sulfur decrease and on crosslinking. The results can be condensed as follows: (1) The kinetics of sulfur disappearance is in every respect qualitatively independent of the chemical constitution of the sulfenamide. (2) For the sulfenamides investigated, the smallest and largest rate constants for sulfur decrease differed only by a factor of two. (3) Greater differences are encountered in the induction times for sulfur decrease and for crosslinking. The latter are notably longer than those for sulfur disappearance. (4) The same activation energy, 23 kcal/mole, is derived from the temperature dependence of the induction times for all the sulfenamides. (5) The dissociation of sulfenamides in solution and their reaction with mercaptobenzothiazole were investigated further. The results provide the basis for a proposed reaction mechanism, which is presented in detail and can account for a number of the features typical of sulfenamide-accelerated vulcanization. (6) The drop in sulfur concentration goes at practically the same rate, if one introduces, instead of N, N-dicyclohexyl-2-benzothiazolesulfenamide, the corresponding ammonium mercaptide in equimolar concentration.

Mechanism of bromination of a quaternary pyrimidinium cation. Change of rate determining step with acidity

1978 ◽  
Vol 56 (23) ◽  
pp. 2970-2976 ◽  
Author(s):  
Oswald S. Tee ◽  
David C. Thackray ◽  
Charles G. Berks
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Aqueous Media ◽  
Stopped Flow ◽  
Flow Method ◽  
High Acidity ◽  
Rate Determining Step ◽  
Kinetics Of ◽  
Good Agreement

The kinetics of bromination of the 1,2-dihydro-1,3-dimethyl-2-oxopyrimidinium cation (Q+) in aqueous media (pH 0–5) have been studied using the stopped-flow method. At the higher acidities (pH < 2) the results are consistent with rate determining attack by bromine upon the pseudobase (QOH), whereas at low acidities (pH > 4) it appears that pseudobase formation is rate determining. The change occurs because at high acidity the reversal of the pseudobase QOH to the cation is fast relative to bromine attack, whereas at low acidity the converse is true. Results obtained at intermediate acidities (pH 2–4) are consistent with this interpretation.A separate kinetic study of pseudobase formation (and decomposition) yielded rate constants in good agreement with those derived from the bromination study.

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