Mercury-photosensitized decomposition of dimethyl ether. Part I. Mechanism

1967 ◽  
Vol 45 (22) ◽  
pp. 2763-2766 ◽  
Author(s):  
L. F Loucks ◽  
K. J Laidler
Keyword(s):  
Mass Balance ◽  
Dimethyl Ether ◽  
Pressure Range ◽  
Reaction Vessel ◽  
No Decomposition ◽  
Methyl Radical ◽  
Reaction Conditions ◽  
Products Of Reaction

The mercury-photosensitized decomposition of dimethyl ether was investigated from 200 to 300 °C and over the pressure range 3 to 600 mm Hg. Measurements were made of the initial rates of formation of the products of reaction, which are CO, H2, C2H6, CH4, CH3OC2H5, and CH3OCH2CH2OCH3. It is concluded that the primary step involves a C—H split; there is no evidence for a primary C—O split. Over the range 200 to 300 °C the methoxymethyl radical, CH3OCH2, decomposed to give formaldehyde and a methyl radical, whereas at 30 °C no decomposition of the CH3OCH2 radical was detected. The mass balance is consistent with the mechanism proposed. The homogeneity of the reaction conditions was examined by varying the concentration of mercury in the reaction vessel.

Mercury-photosensitized decomposition of dimethyl ether. Part II. The thermal decomposition of the methoxymethyl radical

1967 ◽  
Vol 45 (22) ◽  
pp. 2767-2773 ◽  
Author(s):  
Leon F. Loucks ◽  
Keith J. Laidler
Keyword(s):  
Carbon Dioxide ◽  
Dimethyl Ether ◽  
Pressure Range ◽  
High Pressures ◽  
Rate Coefficient ◽  
Rate Coefficients ◽  
Methyl Radical ◽  
Lower Efficiency ◽  
First Order ◽  
Order Rate

The decomposition of the methoxymethyl radical, generated in the mercury-photosensitized decomposition of dimethyl ether, has been investigated over the temperature range 200 to 300 °C and the pressure range 3 to 600 mm Hg. The radical decomposes to give a formaldehyde molecule and a methyl radical. The effects of pressure and temperature on the first-order rate coefficient for the decomposition of the methoxymethyl radical have been examined in detail. The rate coefficient shows a pressure dependence over the full pressure range studied. The order of the decomposition is about 1.4 at the middle of the pressure range studied, with a lower order at higher pressures and a higher order at lower pressures. At 100 mm Hg the observed activation energy for the decomposition of the methoxymethyl radical is 24.8 kcal/mole.The first-order and second-order rate coefficients, k∞ and k0, corresponding to the limiting conditions of high pressures and low pressures respectively, have been evaluated as [Formula: see text]Kassel integrations have been carried out for the methoxymethyl radical and have been fitted to the experimental data. It is concluded that 8 or 9 normal modes contribute to the energization of the radical. The rate coefficient is increased by the presence of carbon dioxide, but carbon dioxide has a lower efficiency than dimethyl ether for the transfer of energy in the energization process.

The thermal decomposition of benzoic acid

1970 ◽  
Vol 48 (24) ◽  
pp. 3797-3801 ◽  
Author(s):  
Keith Winter ◽  
Donald Barton
Keyword(s):  
Thermal Decomposition ◽  
Benzoic Acid ◽  
Pressure Range ◽  
Initial Rate ◽  
Material Balance ◽  
Reaction Vessel ◽  
Radical Processes

The thermal decomposition of benzoic acid has been studied in a Pyrex reaction vessel at 475, 486, and 499 °C over the pressure range 5 to 40 Torr. The main products, CO2 and C6H6, were accompanied by smaller quantities of CO, H2, and biphenyl. The percentage of conversion varied from less than 1% for initial rate experiments to over 90 % in attempts to obtain a material balance. Moderately reproducible initial rates of formation of CO2 were obtained after the vessel had been conditioned by pyrolysis of benzoic acid. The order for the initial rate of formation of CO2, 1.20 ± 0.03 at 475 °C and 1.28 ± 0.04 at 499 °C, is discussed in terms of a combination of first and three-halves order reactions. Formation of both C6H5D and C6H6 in the presence of C6D5CD3 is accepted tentatively as evidence of formation of benzene by both molecular and radical processes.

Individual rate constants of methyl radical reactions in the pyrolysis of dimethyl ether

1977 ◽  
Vol 55 (23) ◽  
pp. 4128-4134 ◽  
Author(s):  
Andrew M. Held ◽  
Kim C. Manthorne ◽  
Philip D. Pacey ◽  
Howard P. Reinholdt
Keyword(s):  
Dimethyl Ether ◽  
Rate Constants ◽  
Flow System ◽  
Average Concentration ◽  
Radical Reactions ◽  
Methyl Radical ◽  
Warm Up ◽  
Secondary Reactions ◽  
Ultraviolet Absorption Spectroscopy ◽  
Individual Rate

Dimethyl ether was pyrolyzed in a flow system at 10 to 80 Torr and 1005 K. The average concentration of CH3 radicals in the reactor was measured by ultraviolet absorption spectroscopy. Product yields were measured by gas chromatography. The system was simulated using a computer program, taking into account the warm-up of the entering gas and the occurrence of secondary reactions. Rate constants were varied to find values consistent with experimental observations. The limiting, high pressure rate constant for the recombination of CH3 was estimated to be 1010.5 ± 0.5ℓ mol−1 s−1. Estimated rate constants for the reactions[Formula: see text]were 107.12 ± 0.2ℓ mol−1 s−1 and 107.5 ± 0.4ℓ mol−1 s−1, respectively.

scholarly journals Methyl Radical Initiated Kharasch and Related Reactions

2020 ◽  
Author(s):  
Nicholas Tappin ◽  
Philippe Renaud
Keyword(s):  
Halogen Atom ◽  
Functional Group ◽  
Chain Process ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Reaction Conditions ◽  
Alternative Source ◽  
Group Transfer ◽  
Radical Trap ◽  
Flash Column Chromatography

An improved procedure to run halogen atom and related chalcogen group transfer radical additions is reported. The procedure relies on the thermal decomposition of di-<i>tert</i>-butylhyponitrite (DTBHN), a safer alternative to the explosive diacetyl peroxide, to produce highly reactive methyl radicals that can initiate the chain process. This mode of initiation generates byproducts that are either gaseous (N<sub>2</sub>) or volatile (acetone and methyl halide) thereby facilitating greatly product purification by either flash column chromatography or distillation. In addition, remarkably simple and mild reaction conditions (refluxing EtOAc during 30 minutes under normal atmosphere) and a low excess of the radical precursor reagent (2.0 equivalents) make this protocol particularly attractive for preparative synthetic applications. This initiation procedure has been demonstrated with a broad scope since it works efficiently to add a range of electrophilic radicals generated from iodides, bromides, selenides and xanthates over a range of unactivated terminal alkenes. A diverse set of radical trap substrates exemplifies a broad functional group tolerance. Finally, di-<i>tert</i>-butyl peroxyoxalate (DTBPO) is also demonstrated as alternative source of <i>tert-</i>butoxyl radicals to initiate these reactions under identical conditions which gives gaseous byproducts (CO<sub>2</sub>).

NO decomposition over La-doped Cu-ZSM5 monolith under adsorption-reaction conditions

2013 ◽  
Vol 464-465 ◽  
pp. 61-67 ◽  
Author(s):  
Gianluca Landi ◽  
Luciana Lisi ◽  
Raffaele Pirone ◽  
Miriam Tortorelli ◽  
Gennaro Russo
Keyword(s):  
No Decomposition ◽  
Reaction Conditions ◽  
Adsorption Reaction ◽  
La Doped

Notizen: High Pressure Reactions, I Evidence for Two Concurrent Mechanisms in Lewis-Acid Catalyzed Alkylation of Aromatics with Olefins

1976 ◽  
Vol 31 (2) ◽  
pp. 277-278 ◽  
Author(s):  
H. Tiltscher ◽  
R. Lohmüller
Keyword(s):  
High Pressure ◽  
Pressure Range ◽  
Reaction Rate ◽  
Initial Reaction Rate ◽  
Product Formation ◽  
Initial Reaction ◽  
Homogeneous Reaction ◽  
Reaction Conditions ◽  
Alkylation Of Benzene ◽  
Acid Catalyzed

A kinetic study was made of the primary step of the alkylation of benzene with propylene and ferric chloride as catalyst under homogeneous reaction conditions at several pressures up to 2 kbar. Initial reaction rate of cumene formation shows a minimum in the medium pressure range, thus indicating that product formation occurs via two different reaction paths with opposite pressure dependence.

Effect of Reaction Conditions on the Catalytic Dehydration of Methanol to Dimethyl Ether Over a K-modified HZSM-5 Catalyst

2017 ◽  
Vol 147 (3) ◽  
pp. 792-801 ◽  
Author(s):  
Sungtak Kim ◽  
Yong Tae Kim ◽  
Chundong Zhang ◽  
Geunjae Kwak ◽  
Ki-Won Jun
Keyword(s):  
Dimethyl Ether ◽  
Reaction Conditions

scholarly journals A Review on the Catalytic Decomposition of NO by Perovskite-Type Oxides

Catalysts ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 622
Author(s):  
Qiuwan Shen ◽  
Shuangshuang Dong ◽  
Shian Li ◽  
Guogang Yang ◽  
Xinxiang Pan
Keyword(s):  
Mixed Oxides ◽  
Low Cost ◽  
Influence Factors ◽  
Catalytic Decomposition ◽  
Catalytic Performance ◽  
No Decomposition ◽  
Reaction Conditions ◽  
A Site ◽  
Perovskite Type ◽  
Decomposition Of No

Direct catalytic decomposition of NO has the advantages of being a simple process, producing no secondary pollution, and being good for the economy, which has attracted extensive research in recent years. Perovskite-type mixed oxides, with an ABO3 or A2BO4 structure, are promising materials as catalysts for NO decomposition due to their low cost, high thermal stability, and, of course, their good catalytic performances. In this review, the influence factors, such as A-site substitution, B-site substitution and reaction conditions on the catalytic performance of catalysts have been expounded. The reaction mechanisms of direct NO decomposition are also discussed. Finally, major conclusions are drawn and some research challenges are highlighted.

scholarly journals Methyl Radical Initiated Kharasch and Related Reactions

2020 ◽  
Author(s):  
Nicholas Tappin ◽  
Philippe Renaud
Keyword(s):  
Halogen Atom ◽  
Functional Group ◽  
Chain Process ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Reaction Conditions ◽  
Alternative Source ◽  
Group Transfer ◽  
Radical Trap ◽  
Flash Column Chromatography

An improved procedure to run halogen atom and related chalcogen group transfer radical additions is reported. The procedure relies on the thermal decomposition of di-<i>tert</i>-butylhyponitrite (DTBHN), a safer alternative to the explosive diacetyl peroxide, to produce highly reactive methyl radicals that can initiate the chain process. This mode of initiation generates byproducts that are either gaseous (N<sub>2</sub>) or volatile (acetone and methyl halide) thereby facilitating greatly product purification by either flash column chromatography or distillation. In addition, remarkably simple and mild reaction conditions (refluxing EtOAc during 30 minutes under normal atmosphere) and a low excess of the radical precursor reagent (2.0 equivalents) make this protocol particularly attractive for preparative synthetic applications. This initiation procedure has been demonstrated with a broad scope since it works efficiently to add a range of electrophilic radicals generated from iodides, bromides, selenides and xanthates over a range of unactivated terminal alkenes. A diverse set of radical trap substrates exemplifies a broad functional group tolerance. Finally, di-<i>tert</i>-butyl peroxyoxalate (DTBPO) is also demonstrated as alternative source of <i>tert-</i>butoxyl radicals to initiate these reactions under identical conditions which gives gaseous byproducts (CO<sub>2</sub>).

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