KINETICS AND MECHANISMS OF THE PYROLYSIS OF DIMETHYL ETHER: I. THE UNINHIBITED REACTION

1963 ◽  
Vol 41 (8) ◽  
pp. 1984-1992 ◽  
Author(s):  
D. J. McKenney ◽  
K. J. Laidler
Keyword(s):  
Experimental Study ◽  
Thermal Decomposition ◽  
Kinetic Parameters ◽  
Dimethyl Ether ◽  
Rate Constant ◽  
Hydrogen Sulphide ◽  
Pressure Range ◽  
Significant Contribution ◽  
Surface Effect ◽  
Elementary Processes

An experimental study has been made of the thermal decomposition of dimethyl ether, the temperature range being 500 to 550 °C and the pressure range 100 to 700 mm Hg. A considerable surface effect was noted, and the results were not very reproducible. The reaction was of the three-halves order and the rate constant could be expressed as 2.98 × 1014e−54,900/RT cc1/2 mole−1/2 sec−1. On the basis of the results obtained in the presence of hydrogen sulphide (D. J. McKenney and K. J. Laidler. Can. J. Chem. 41, 2009 (1963)) it is concluded that the initiating step, the dissociation of CH3OCH3 into CH3O and CH3, is in its second-order region. In order for the overall order to be three-halves the main terminating step must be either of the type ββM or βμ. The concentrations of the various radicals, and the rates of the various chain-ending steps, are calculated from known or estimated kinetic parameters for the elementary processes. It is concluded that the predominant chain-ending step is probably CH3 + CH3 + M → C2H6 + N, but that there may be a significant contribution from CH3 + CHO + M → CH3CHO + M and from CH3 + CH2OCH3 + M → C2H5OCH3 + M.

Thermal Decomposition of Diethylketone Cyclic Triperoxide in Polar Solvents

2014 ◽  
Vol 67 (6) ◽  
pp. 881 ◽  
Author(s):  
Gastón P. Barreto ◽  
Elida E. Alvarez ◽  
Gladys N. Eyler ◽  
Adriana I. Cañizo ◽  
Patricia E. Allegretti
Keyword(s):  
Thermal Decomposition ◽  
Hydrogen Atom ◽  
Physicochemical Properties ◽  
Kinetic Parameters ◽  
Rate Constant ◽  
Decomposition Mechanism ◽  
Secondary Alcohols ◽  
Polar Solvents ◽  
Secondary Carbon

The thermolysis of diethylketone cyclic triperoxide (3,3,6,6,9,9-hexaethyl-1,2,4,5,7,8-hexaoxacyclononane, DEKTP) was studied in different polar solvents (ethanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, and acetonitrile). The rate constant values (kd) are higher for reactions performed in secondary alcohols probably because of the possibility to form a cyclic adduct with the participation of the hydrogen atom bonded to the secondary carbon. The kinetic parameters were correlated with the physicochemical properties of the selected solvents. The products of the DEKTP thermal decomposition in different polar solvents support a radical-based decomposition mechanism.

Determination of the bond dissociation energy, D(CH3Hg—CH3), by the toluene carrier method

1969 ◽  
Vol 47 (6) ◽  
pp. 991-994 ◽  
Author(s):  
R. J. Kominar ◽  
S. J. Price
Keyword(s):  
Thermal Decomposition ◽  
Excellent Agreement ◽  
Rate Constant ◽  
Pressure Range ◽  
Arrhenius Equation ◽  
Flow System ◽  
Methyl Radicals ◽  
Exponential Factors ◽  
Pressure Independent

The thermal decomposition of Hg(CH3)2 has been studied in a toluene carrier flow system over the pressure range 4.5 to 323 mm at temperatures of 422 to 527 °C. The Arrhenius equation for the pressure independent region,[Formula: see text]is in excellent agreement with earlier work on the fully inhibited decomposition at lower temperatures. The region of fall off of the unimolecular rate constant is in agreement with a classical Kassel calculation using s = 16−18, but the rate of fall off requires the use of a curve with s = 3, displaced five log units to the left. This is consistent with the previous results for the dissociation of ethane into two methyl radicals and is further evidence of the inability of the classical Kassel equation to represent the behavior of systems with high pre-exponential factors.

KINETICS AND MECHANISMS OF THE PYROLYSIS OF DIMETHYL ETHER: III. THE REACTION ACCELERATED BY HYDROGEN SULPHIDE

1963 ◽  
Vol 41 (8) ◽  
pp. 2009-2019 ◽  
Author(s):  
D. J. McKenney ◽  
K. J. Laidler
Keyword(s):  
Dimethyl Ether ◽  
Rate Constant ◽  
Hydrogen Sulphide ◽  
Relative Rate ◽  
Order Rate Constant ◽  
Linear Increase ◽  
Order Rate ◽  
A Value ◽  
Sulphide Concentration ◽  
Principal Chain

The thermal decomposition of dimethyl ether in the presence of hydrogen sulphide was studied in the temperature range of 480 to 530 °C, and over the pressure range of 5 to 500 mm of Hg. For a given pressure of dimethyl ether the rate of decomposition increased with the addition of increasing quantities of hydrogen sulphide, reaching a plateau after approximately 30% H2S had been added. The relative rate of decomposition then remained constant until more than 50% H2S had been added. Further increase in the hydrogen sulphide concentration produced a linear increase in the relative rate. In the region between 30 and 50% added H2S, the decomposition of dimethyl ether was three-halves order with respect to ether pressure, and zero order with respect to hydrogen sulphide pressure. In this region the three-halves-order rate constant can be expressed by k = 1.06 × 1014e−53,200/RT cc1/2 mole−1/2 sec−1. In the region beyond 50% added H2S, the reaction was first order with respect to dimethyl ether, and one-half order with respect to hydrogen sulphide. In this region the three-halves-order rate constant is given by k = 4.98 × 1014e−52,500/RT cc1/2 mole−1/2 sec−1. The experimental facts are shown to be consistent with a mechanism involving hydrosulphide radicals as the principal chain carriers. These HS radicals are produced mainly from the reaction of methyl radicals with hydrogen sulphide. The work leads to a value of 85.6 kcal for the dissociation energy of H2S into H + SH.

Regeneration Mechanism Studied by Potential-Time Response to Sinusoidal Current-Time Function

1997 ◽  
Vol 62 (10) ◽  
pp. 1511-1526
Author(s):  
María-Luisa Alcaraz ◽  
Ángela Molina
Keyword(s):  
Kinetic Parameters ◽  
Rate Constant ◽  
Theoretical Study ◽  
Time Function ◽  
Time Response ◽  
Current Time ◽  
Regeneration Mechanism ◽  
Sinusoidal Current ◽  
Regeneration Processes

A theoretical study of the potential-time response to sinusoidal current applied to static and dynamic electrodes for regeneration processes is presented. Methods for determination of the regeneration fraction, rate constant of the chemical reaction and heterogeneous kinetic parameters are proposed.

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.

The reaction of μ-oxo-bis(phthalocyaninato)iron(III) with hydrogen sulphide in the presence of pyridine: Evidence for axial coordination of dichloromethane

2005 ◽  
Vol 09 (03) ◽  
pp. 198-205 ◽  
Author(s):  
Fabrizio Monacelli ◽  
Elisa Viola
Keyword(s):  
Reaction Mechanism ◽  
Linear Function ◽  
Rate Constant ◽  
Hydrogen Sulphide ◽  
Stoichiometric Ratio ◽  
First Order ◽  
Axial Coordination ◽  
Elementary Sulphur ◽  
Increasing Function ◽  
Limiting Value

The oxo-bridged complex ( py ) FePc - O - FePc ( py ) ( py = pyridine , Pc = phthalocyaninato dianion) reacts in dichloromethane with hydrogen sulphide giving elementary sulphur and the reduced ( py )2( FePc ) complex in the stoichiometric ratio 1:1. Under excess py and H2S , the reaction is first-order and the rate constant at a given py concentration is an increasing function of the reducing agent concentration, with asymptotic tendency to a limiting value. This latter depends on the pyridine concentration being higher the lower is the base concentration. When the reaction is carried out in pure pyridine, the rate constant is, instead, a strictly linear function of [ H2S ], with zero intercept. A reaction mechanism is proposed where the dichloromethane is directly involved in the axial coordination about the iron centers and H2S competes efficiently with both pyridine and solvent.

Sign in / Sign up

Export Citation Format

Share Document