scholarly journals Thermokinetic study of the inactivation reaction of 1-methyl phthalazinium ylids

2003 ◽  
Vol 68 (6) ◽  
pp. 447-454
Author(s):  
Maria Carposu ◽  
Lucia Odochian ◽  
St. Dima ◽  
M. Dumitras ◽  
Magda Petrovanu
Keyword(s):  
Experimental Data ◽  
Rate Constants ◽  
Reaction Order ◽  
Thermodynamic Study ◽  
Chemical Affinity ◽  
Benzoyl Radical

The present paper consists in a thermokinetic study on the dimerization reactions of 1-methylphthalazinium ylids with ?NO2 (ylid 1) and respectively, ?O?CH3 (ylid 2) substituents in the p position of the benzoyl radical bound to the ylidic carbanion. From experimental data, the reaction order and rate constants have been calculated. The reaction order n = 2 confirmed the ylids? dimerization reactions, while the values of the rate constants, k2 = 3.093x10-2L/mol s and, respectively, 2.16 x?10-1 L/mol s for the dimerization of ylids 1 and 2 made evident the higher reactivity of ylid 2 versus ylid 1. The same conclusion is also supported by the results of the thermodynamic study based on the chemical affinity of the two reactions, when Ao dim,1 < Aodim,2.

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.

scholarly journals Force Dependence of Velocity and Run Length of Kinesin-1, Kinesin-2 and Kinesin-5 Family Molecular Motors

Molecules ◽  
2019 ◽  
Vol 24 (2) ◽  
pp. 287 ◽  
Author(s):  
Si-Kao Guo ◽  
Wei-Chi Wang ◽  
Peng-Ye Wang ◽  
Ping Xie
Keyword(s):  
Experimental Data ◽  
Atpase Activity ◽  
Rate Constants ◽  
Molecular Motors ◽  
Quantitative Agreement ◽  
Run Length ◽  
Movement Dynamics ◽  
Proposed Model ◽  
Movement Mechanism ◽  
The Difference

Kinesin-1, kinesin-2 and kinesin-5 are three families of a superfamily of motor proteins; which can walk processively on microtubule filaments by hydrolyzing ATP. It was experimentally shown that while the three kinesin dimers show similar feature on the force dependence of velocity, they show rather different features on the force dependence of run length. However, why the three families of kinesins show these rather different features is unclear. Here, we computationally studied the movement dynamics of the three dimers based on our proposed model. The simulated results reproduce well the available experimental data on the force dependence of velocity and run length. Moreover, the simulated results on the velocity and run length for the three dimers with altered neck linker lengths are also in quantitative agreement with the available experimental data. The studies indicate that the three families of kinesins show much similar movement mechanism and the rather different features on the force dependence of run length arise mainly from the difference in rate constants of the ATPase activity and neck linker docking. Additionally, the asymmetric (limping) movement dynamics of the three families of homodimers with and without altered neck linker lengths are studied, providing predicted results.

Calculated R.R.K.M. unimolecular dissociation rate constants for hydrazine

1969 ◽  
Vol 47 (14) ◽  
pp. 2593-2599 ◽  
Author(s):  
D. W. Setser ◽  
W. C. Richardson
Keyword(s):  
Experimental Data ◽  
Lower Bounds ◽  
Rate Constants ◽  
Chemical Activation ◽  
Dissociation Rate ◽  
Upper And Lower Bounds ◽  
Unimolecular Dissociation ◽  
Complex Models ◽  
Dissociation Rate Constants ◽  
Activated Complex

Unimolecular rate constants for hydrazine dissociation by thermal and chemical activation have been calculated according to the R.R.K.M. theory. The two activated complex models used in the calculations represent plausible upper and lower bounds to the rate constants. The calculations are mainly directed toward establishing expected decomposition to stablilization ratios of N2H4 produced by combination of NH2 radicals; however, a general comparison to available experimental data for hydrazine dissociation is made.

The Rate-Constant for the Recombination of Methyl Radicals

1986 ◽  
Vol 39 (8) ◽  
pp. 1257 ◽  
Author(s):  
NL Arthur ◽  
JC Biordi
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Rate Constant ◽  
Rate Constants ◽  
The Other ◽  
Methyl Radicals ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Best Value ◽  
Limiting Value

Rate constants for the recombination of CH3 radicals have been measured by means of the rotating sector technique in the temperature range 373- 463 K, and at a pressure of 30 Torr . CH3 radicals were produced by the photolysis of acetone, and the experimental data were fitted to sector curves generated from Shepp's theory. The results give kb = (2.81�0.22)×1013 cm3 mol-1 s-1, which, under the chosen experimental conditions, is close to its high-pressure limiting value. A comparison is made with the other values of the rate constant reported in the literature, and a best value is suggested.

Simulation of Crosslink and Graft Mechanism of Hydrogenated-NBR/ZINC Di-Methacrylate Composites by Moving Die Rheometer

2002 ◽  
Vol 75 (5) ◽  
pp. 943-954 ◽  
Author(s):  
Takashi Sato ◽  
Akio Fujino ◽  
Sachio Hayashi ◽  
Motofumi Oyama ◽  
Katsumichi Ono
Keyword(s):  
Experimental Data ◽  
Genetic Algorithm ◽  
Rate Constants ◽  
Reaction Rate ◽  
Addition Reaction ◽  
Algorithm Optimization ◽  
Reaction Rate Constants ◽  
Data Comparison ◽  
Graft Reaction ◽  
Comparison With Experimental Data

Abstract This paper studies the crosslink and graft mechanism of hydrogenated-NBR/zinc di-methacrylate (HNBR/ZDMA) composites. The experiments to determine the rate constants of crosslink and graft reaction formulas are from Moving Die Rheometer (MDR) data. Comparison with experimental data and the solution of simultaneous ordinary differential equations for the crosslink and graft reactions are performed. Genetic algorithm optimization of the reaction rate constants allowed for simulation of crosslinking and graft reaction process. This simulation predicts that the HNBR/peroxide cure system will contain 0.1052-mole/l crosslink between matrix HNBR polymer at 2 phr.-peroxide concentration. The crosslink concentration of 0.1052-mole/l is composed of 0.0308-mole/l-addition reaction and 0.0744-mole/l-termination reaction. Moreover, the HNBR/ZDMA cure system contains 0.0148-mole/l graft of poly-ZDMA to HNBR and 0.0903-mole/l crosslink between matrix HNBR polymer at a 2 phr.-peroxide concentration.

scholarly journals Chamber simulation of photooxidation of dimethyl sulfide and isoprene in the presence of NO<sub>x</sub>

2012 ◽  
Vol 12 (21) ◽  
pp. 10257-10269 ◽  
Author(s):  
T. Chen ◽  
M. Jang
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Rate Constants ◽  
Dimethyl Sulfide ◽  
Model Simulation ◽  
Methanesulfonic Acid ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Gaseous Products ◽  
Dms Oxidation

Abstract. To improve the model prediction for the formation of H2SO4 and methanesulfonic acid (MSA), aerosol-phase reactions of gaseous dimethyl sulfide (DMS) oxidation products [e.g., dimethyl sulfoxide (DMSO)] in aerosol have been included in the DMS kinetic model with the recently reported gas-phase reactions and their rate constants. To determine the rate constants of aerosol-phase reactions of both DMSO and its major gaseous products [e.g., dimethyl sulfone (DMSO2) and methanesulfinic acid (MSIA)], DMSO was photooxidized in the presence of NOx using a 2 m3 Teflon film chamber. The rate constants tested in the DMSO kinetic mechanisms were then incorporated into the DMS photooxidation mechanism. The model simulation using the newly constructed DMS oxidation mechanims was compared to chamber data obtained from the phototoxiation of DMS in the presence of NOx. Within 120-min simulation, the predicted concentrations of MSA increase by 200–400% and those of H2SO4, by 50–200% due to aerosol-phase chemistry. This was well substantiated with experimental data. To study the effect of coexisting volatile organic compounds, the photooxidation of DMS in the presence of isoprene and NOx has been simulated using the newly constructed DMS kinetic model integrated with the Master Chemical Mechanism (MCM) for isoprene oxidation, and compared to chamber data. With the high concentrations of DMS (250 ppb) and isoprene (560–2248 ppb), both the model simulation and experimental data showed an increase in the yields of MSA and H2SO4 as the isoprene concentration increased.

A KINETIC STUDY OF THE METATHETICAL AND ADDITION REACTIONS CHARACTERISTIC OF ALLYL POLYMERIZATION

1962 ◽  
Vol 40 (4) ◽  
pp. 796-803 ◽  
Author(s):  
A. C. R. Brown ◽  
D. G. L. James
Keyword(s):  
Experimental Data ◽  
Free Radicals ◽  
Gas Phase ◽  
Rate Constants ◽  
Allyl Alcohol ◽  
Reasonable Agreement ◽  
Chain Transfer ◽  
Addition Reactions ◽  
Radical Reactivity ◽  
Transfer Processes

The rate constants of the reactions[Formula: see text]have been measured in the gas phase between 50° and 142 °C:[Formula: see text]where ki is the (known) rate constant for the reaction[Formula: see text]The significance of these values is discussed in relation to the propagation and chain transfer processes in the polymerization of allyl alcohol. A consideration of the rates of addition of free radicals to a series of monomers of diverse reactivity reveals that a correlation exists between the rate constants for the addition of the ethyl radical in the gas phase and of certain polymer radicals in the liquid phase.An application of the general equation proposed by Bamford, Jenkins, and Johnston for radical reactivity leads to the conclusion that kp ≈ 2k7 and that kP/kf ≈ k7/k6 = 1.8 for allyl alcohol at 60 °C. Predictions based upon these relationships are compared with experimental data for the propagation and degree of homopolymerization of allyl alcohol and for inhibition and propagation in copolymerization; reasonable agreement is found in all cases.

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