Kinetics and mechanism of unimolecular decomposition of 3-methyl-1-p-tolyltriazene

1981 ◽  
Vol 59 (6) ◽  
pp. 923-926 ◽  
Author(s):  
Keith Vaughan ◽  
Michael T. H. Liu
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Kinetic Parameters ◽  
Kinetics And Mechanism ◽  
Unimolecular Decomposition ◽  
Mechanism Of Degradation

Kinetic parameters (Ea and ΔS≠) for the thermolysis of 3-methyl-1-p-tolyltriazene (1) in tetrachloroethylene have been determined. The near-zero value for ΔS≠ suggests a transition state with minimal stretching of the N—N bonds in tautomers 1a or 1b. The activation energy (Ea = 29.2 kcal/mol) and ΔS≠ for the decomposition of 1 are very similar to those of the azoarylalkanes (Ar—N=N—R), suggesting a similar mechanism of degradation. The major products of the thermolysis of 1 are p-toluidine, N-methyl-p-toluidine, and p-chlorotoluene, which are rationalized in terms of homolytic breakdown of both tautomers.

Microscopic Interpretation of Arrhenius Parameters

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Transition State Theory ◽  
Average Energy ◽  
Zero Point ◽  
State Theory ◽  
Exponential Factor ◽  
Quantum Tunnelling ◽  
Microscopic Interpretation ◽  
The Difference

This chapter reviews the microscopic interpretation of the pre-exponential factor and the activation energy in rate constant expressions of the Arrhenius form. The pre-exponential factor of apparent unimolecular reactions is, roughly, expected to be of the order of a vibrational frequency, whereas the pre-exponential factor of bimolecular reactions, roughly, is related to the number of collisions per unit time and per unit volume. The activation energy of an elementary reaction can be interpreted as the average energy of the molecules that react minus the average energy of the reactants. Specializing to conventional transition-state theory, the activation energy is related to the classical barrier height of the potential energy surface plus the difference in zero-point energies and average internal energies between the activated complex and the reactants. When quantum tunnelling is included in transition-state theory, the activation energy is reduced, compared to the interpretation given in conventional transition-state theory.

Application of Calculus Equation in Solving Thermal Decomposition Kinetics Parameters of Flame Retardant Wood

2014 ◽  
Vol 983 ◽  
pp. 190-193
Author(s):  
Cai Yun Sun ◽  
Yong Li Yang ◽  
Ming Gao
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Thermal Degradation ◽  
Phosphoric Acid ◽  
Flame Retardant ◽  
Kinetic Parameters ◽  
Flame Retardancy ◽  
Decomposition Kinetics ◽  
Thermal Decomposition Kinetics ◽  
Kinetics Parameters

Wood has been treated with amino resins and amino resins modified with phosphoric acid to impart flame retardancy. The thermal degradation of samples has been studied by thermogravimetry (TG) in air. From the resulting data, kinetic parameters for different stages of thermal degradation are obtained following the method of Broido. For the decomposition of wood and flame retardant wood, the activation energy is found to decrease from 122 to 72 kJmol-1.

Thermogravimetric Analysis of Glucose-Based and Fructose-Based Carbohydrates

2013 ◽  
Vol 805-806 ◽  
pp. 265-268 ◽  
Author(s):  
Fang Ming Cui ◽  
Xiao Yuan Zhang ◽  
Li Min Shang
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Kinetic Parameters ◽  
Degree Of Polymerization ◽  
Experiment Data ◽  
Pyrolysis Characteristics ◽  
The Difference ◽  
Kinetic Calculations

Thermogravimetric analysis (TGA) was employed to study the pyrolysis characteristics of four glucose-based and three fructose-based carbohydrates. Kinetic parameters were calculated based on the experiment data. The results indicated that the starting and maximal pyrolysis temperatures of the glucose-based carbohydrates were increased steadily as the rising of their degree of polymerization (DP). The fructose-based carbohydrates exhibited similar pyrolysis behaviors as the glucose-based carbohydrates, but the difference was smaller. Kinetic calculations revealed that the activation energy values of the glucose-based carbohydrates were higher than those of the fructose-based carbohydrates, indicating the glucose-based carbohydrates were more difficult to decompose than the fructose-based carbohydrates.

scholarly journals Kinetic Analysis of the Effect of Poliovirus Receptor on Viral Uncoating: the Receptor as a Catalyst

2001 ◽  
Vol 75 (11) ◽  
pp. 4984-4989 ◽  
Author(s):  
Simon K. Tsang ◽  
Brian M. McDermott ◽  
Vincent R. Racaniello ◽  
James M. Hogle
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Kinetic Analysis ◽  
Transition State Theory ◽  
State Theory ◽  
Viral Receptor ◽  
Poliovirus Receptor ◽  
Entropic Stabilization ◽  
Entropic Effects

ABSTRACT We examined the role of soluble poliovirus receptor on the transition of native poliovirus (160S or N particle) to an infectious intermediate (135S or A particle). The viral receptor behaves as a classic transition state theory catalyst, facilitating the N-to-A conversion by lowering the activation energy for the process by 50 kcal/mol. In contrast to earlier studies which demonstrated that capsid-binding drugs inhibit thermally mediated N-to-A conversion through entropic stabilization alone, capsid-binding drugs are shown to inhibit receptor-mediated N-to-A conversion through a combination of enthalpic and entropic effects.

scholarly journals Thermal Degradation Behaviour of Ni(II) Complex of 3,4-Methylenedioxaphenylaminoglyoxime

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Emin Karapınar ◽  
Ilkay Hilal Gubbuk ◽  
Bilge Taner ◽  
Pervin Deveci ◽  
Emine Ozcan
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermal Degradation ◽  
Metal Complex ◽  
Kinetic Parameters ◽  
Preexponential Factor ◽  
Degradation Behaviour ◽  
Mechanism Of Decomposition ◽  
Pyrolytic Decomposition

Thermal degradation behaviour of the Ni(II) complex of 3,4-methylenedioxaphenylaminoglyoxime was investigated by TG, DTA, and DTG at a heating rate of 10°C min−1under dinitrogen. The acquired experimental data shows that the complex is thermally stable up to 541 K. The pyrolytic decomposition process occurs by melting metal complex and metal oxide remains as final product. The energies of the reactions involved and the mechanism of decomposition at each stage have been examined. The values of kinetic parameters such as activation energy (E), preexponential factor (A) and thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) are also evaluated.

scholarly journals Advances in Automated Transition State Theory Calculations: Improvements on the AutoTST Framework

2020 ◽  
Author(s):  
Nathan Harms ◽  
Carl Underkoffler ◽  
Richard West
Keyword(s):  
Transition State ◽  
Kinetic Parameters ◽  
Transition State Theory ◽  
Vibrational Analysis ◽  
Chemical Kinetic ◽  
State Theory ◽  
Combustion Chemistry ◽  
Transition State Geometry ◽  
Substantial Progress ◽  
Symmetry Number

<div>Kinetic modeling of combustion chemistry has made substantial progress in recent years with the development of increasingly detailed models. However, many of the chemical kinetic parameters utilized in detailed models are estimated, often inaccurately. To help replace rate estimates with more accurate calculations, we have developed AutoTST, an automated Transition State Theory rate calculator. This work describes improvements to AutoTST, including: a systematic conformer search to find an ensemble of low energy conformers, vibrational analysis to validate transition state geometries, more accurate symmetry number calculations, and a hindered rotor treatment when deriving kinetics. These improvements resulted in location of transition state geometry for 93% of cases and generation of kinetic parameters for 74% of cases. Newly calculated parameters agree well with benchmark calculations and perform well when used to replace estimated parameters in a detailed kinetic model of methanol combustion.</div>

Kinetics and Mechanism of the Aminolysis of S-Aryl O-Ethyl Dithiocarbonates in Acetonitrile

2004 ◽  
Vol 69 (12) ◽  
pp. 2174-2182 ◽  
Author(s):  
Hyuck Keun Oh ◽  
Ji Young Oh ◽  
Dae Dong Sung ◽  
Ikchoon Lee
Keyword(s):  
Transition State ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Interaction Constant ◽  
Kinetics And Mechanism ◽  
Cyclic Structure ◽  
Concerted Mechanism ◽  
Tetrahedral Intermediate ◽  
Kinetic Isotope ◽  
Hydrogen Bonded

The aminolysis of S-aryl O-ethyl dithiocarbonates with benzylamines are studied in acetonitrile at -25.0 °C. The βX (βnuc) values are in the range 0.67-0.77 with a negative cross-interaction constant, ρXZ = -0.24, which are interpreted to indicate a concerted mechanism. The kinetic isotope effects involving deuterated benzylamine nucleophiles (XC6H4CH2ND2) are large, kH/kD = 1.41-1.97, suggesting that the N-H(D) bond is partially broken in the transition state by forming a hydrogen-bonded four-center cyclic structure. The concerted mechanism is enforced by the strong push provided by the EtO group which enhances the nucleofugalities of both benzylamine and arenethiolate from the putative zwitterionic tetrahedral intermediate.

Selectivity in carbon–carbon coupling reactions at palladium(IV) and platinum(IV)

2019 ◽  
Vol 97 (7) ◽  
pp. 529-537 ◽  
Author(s):  
Richard J. Puddephatt
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Computational Study ◽  
Bond Formation ◽  
Reductive Elimination ◽  
Organometallic Complexes ◽  
Axial Position ◽  
Coupling Reactions ◽  
Methyl Group ◽  
Trigonal Bipyramidal

The isomerization and reductive elimination reactions from octahedral organometallic complexes of palladium(IV) and platinum(IV) usually occur through five-coordinate intermediates that cannot be directly detected. This paper reports a computational study of five-coordinate complexes of formulae [PtMe3(bipy)]+, [PtMe2Ph(bipy)]+, and [PtMe(CH2CMe2C6H4)(bipy)]+ (M = Pd or Pt, bipy = 2,2′-bipyridine), particularly with respect to reactivity and selectivity in reductive elimination. All of the complexes are predicted to have square pyramidal structures with the bipy and two R groups in the equatorial positions and one R group in the axial position, and axial–equatorial exchange occurs by a pairwise mechanism, with the transition state having a pinched trigonal bipyramidal (PTBP) stereochemistry, with one nitrogen and two R groups in the trigonal plane. The activation energy for isomerization is lower than that for reductive elimination in all cases. For the complexes [MMe2Ph(bipy)]+, the activation energies for reductive elimination with Me–Me or Me–Ph coupling are similar. For the complexes [MMe(CH2CMe2C6H4)(bipy)]+, the reductive elimination with Me–C6H4 bond formation from the isomer with the methyl group in the axial position is predicted and is attributed to it having the best conformation of the Me and C6H4 groups for C–C bond formation. In all cases, the selectivity for reductive elimination is similar for M = Pd or Pt, but reactivity is higher for M = Pd. The relevance of this work to selectivity in catalysis is discussed.

scholarly journals Pyrolysis Kinetic Parameters of Omari Oil Shale Using Thermogravimetric Analysis

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4060
Author(s):  
Ziad Abu El-Rub ◽  
Joanna Kujawa ◽  
Samer Al-Gharabli
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Kinetic Parameters ◽  
Oil Shale ◽  
Arrhenius Plot ◽  
Frequency Factor ◽  
Coefficient Of Determination ◽  
Assay Method ◽  
Temperature Integral ◽  
Integral Approximation

Oil shale is one of the alternative energies and fuel solutions in Jordan because of the scarcity of conventional sources, such as petroleum, coal, and gas. Oil from oil shale reservoirs can be produced commercially by pyrolysis technology. To optimize the process, mechanisms and rates of reactions need to be investigated. Omari oil shale formation in Jordan was selected as a case study, for which no kinetic models are available in the literature. Oil shale was analyzed using the Fischer assay method, proximate analysis (moisture, volatile, and ash), gross calorific value, elemental analysis (CHNS), and X-ray fluorescence (XRF) measurements. Non-isothermal thermogravimetric analysis was applied to study the kinetic parameters (activation energy and frequency factor) at four selected heating rates (5, 10, 15, and 20 °C/min). When oil shale was heated from room temperature to 1100 °C, the weight loss profile exhibited three different zones: drying (devolatilization), pyrolysis, and mineral decomposition. For each zone, the kinetic parameters were calculated using three selected methods: integral, temperature integral approximation, and direct Arrhenius plot. Furthermore, the activation energy in the pyrolysis zone was 112–116 kJ/mol, while the frequency factor was 2.0 × 107 − 1.5 × 109 min−1. Moreover, the heating rate has a directly proportional relationship with the rate constant at each zone. The three different methods gave comparable results for the kinetic parameters with a higher coefficient of determination (R2) for the integral and temperature integral approximation compared with the direct Arrhenius plot. The determined kinetic parameters for Omari formation can be employed in developing pyrolysis reactor models.

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