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 Initial Stages of the Pyrolysis of Dimethyl Ether

1975 ◽  
Vol 53 (18) ◽  
pp. 2742-2747 ◽  
Author(s):  
Philip D. Pacey
Keyword(s):  
Dimethyl Ether ◽  
Rate Constant ◽  
Arrhenius Plot ◽  
Flow System ◽  
Order Rate Constant ◽  
Chain Termination ◽  
Rate Coefficients ◽  
First Order ◽  
Order Rate ◽  
Initiation Reaction

Dimethyl ether was pyrolized in a flow system at 782–936 K and 25–395 Torr with conversions from 0.2–10%. Product analyses were consistent with a simple Rice–Herzfeld mechanism with most chain termination by the recombination of CH3 radicals. The rate coefficients for both the initiation and termination reactions appeared to be slightly pressure dependent. The first-order rate constant for the initiation reaction,[Formula: see text]calculated from the rate of C2H6 formation, was k1 = 1015.0±0.5exp (−318 ± 8 kJ mol−1/RT) s−1, corresponding to ΔHf0(CH3O) = −5 ± 8 kJmol−1. Comparison of CH4 and C2H6 yields enabled calculation of the rate constant for the reaction of CH3 with dimethyl ether. From 373−936 K, the Arrhenius plot for this reaction is a curve.

THE KINETICS OF THE DECOMPOSITION REACTIONS OF THE LOWER PARAFFINS: II. ISOBUTANE

1938 ◽  
Vol 16b (8) ◽  
pp. 260-272 ◽  
Author(s):  
E. W. R. Steacie ◽  
I. E. Puddington
Keyword(s):  
Rate Constants ◽  
Pressure Range ◽  
Reaction Rate ◽  
High Pressures ◽  
Initial Pressure ◽  
First Order ◽  
Decomposition Reactions ◽  
Order Rate ◽  
Reaction Proceeds ◽  
Kinetics Of

The kinetics of the thermal decomposition of isobutane has been investigated over an initial pressure range of from 5 to 60 cm., and at temperatures from 522 to 582 °C. The initial first order rate constants at high pressures are given by[Formula: see text]The results are in general agreement with those obtained by previous investigators. The reaction rate falls off with diminishing pressure, and the first order rate constants in a given run diminish strongly as the reaction proceeds. This behavior is similar to that of n-butane.Analyses of the products of the reaction were made at various stages, temperatures, and initial pressures by low-temperature distillation in a still of the Podbielniak type. The initial products were found by extrapolation to be H2, 35; CH4, 14; C2H4, 0.9; C2H6, 0.9; C3H6, 14; and C4H8, 35%. The results are compared with those of other workers.

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.

The thermal decompositions of carbamates. I. Ethyl N-Methyl-N-phenylcarbamate

1971 ◽  
Vol 24 (12) ◽  
pp. 2541 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Rate Constants ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
First Order ◽  
Order Rate

Ethyl N-methyl-N-phenylcarbamate decomposes in the gas phase over the range 329-380� to give N-methylaniline, carbon dioxide, and ethylene. The reaction is quantitative, and is first order in the carbamate. First-order rate constants are described by the equation ������������������� k1 = 1012.44 exp(-45,380/RT) (s-1) and are unaffected by the addition of cyclohexene or by increase in the surface to volume ratio of the reaction vessel. The reaction is considered to be unimolecular and likely to proceed by means of a mechanism of the type represented by the pyrolyses of acetates, xanthates, and carbonates.

Models to Determine First-Order Rate Coefficients from Single-Well Push-Pull Tests

Ground Water ◽  
2006 ◽  
Vol 44 (2) ◽  
pp. 275-283 ◽  
Author(s):  
Martin H. Schroth ◽  
Jonathan D. Istok
Keyword(s):  
Rate Coefficients ◽  
First Order ◽  
Order Rate ◽  
Single Well ◽  
Pull Tests

Kinetics of aquation of the fluoropentaamminecobalt(III) ion

1970 ◽  
Vol 48 (7) ◽  
pp. 1054-1058 ◽  
Author(s):  
T. W. Swaddle ◽  
W. E. Jones
Keyword(s):  
Ionic Strength ◽  
Rate Coefficient ◽  
Hydrogen Ion ◽  
Fluoride Ion ◽  
Kcal Mole ◽  
First Order ◽  
Order Rate ◽  
Relationship Of ◽  
The Relationship ◽  
Kinetics Of

The kinetics of the hydrogen-ion-independent pathway for the replacement of fluoride in aqueous (NH3)5CoF2+ by H2O have been reinvestigated using a specific fluoride-ion electrode, with due regard for the concomitant autocatalytic loss of the ammine ligands. In perchlorate media of ionic strength 0.1 M, the first-order rate coefficient is 1.22 × 10−6 s−1 at 45°, and the kinetics are represented by ΔH* = 24.4 kcal mole−1 and ΔS* = −9 cal deg−1 mole−1 over the range 35–75° at least. The relationship of these data to those for the aquation of other species of the type ML5Xn+ is discussed.

Mechanistic Information on the Aquations of Complexes of the Pentaamminecobalt(III) Series from Kinetic Studies at High Pressures

1972 ◽  
Vol 50 (17) ◽  
pp. 2739-2746 ◽  
Author(s):  
W. E. Jones ◽  
L. R. Carey ◽  
T. W. Swaddle
Keyword(s):  
High Pressures ◽  
Rate Coefficient ◽  
Kinetic Studies ◽  
Quadratic Equation ◽  
Water Molecules ◽  
First Order ◽  
Unit Slope ◽  
Straight Line ◽  
The Mean ◽  
The Stability

The logarithm of the pseudo-first-order rate coefficient k for the aquation of Co(NH3)5X(3–n)+ can be represented by a quadratic equation in the pressure P, or, better, by[Formula: see text]where P is in kbar, [Formula: see text] is the volume of activation at P = 0, and x is the increase in the number of water molecules solvating the complex as it goes to the transition state. For [Formula: see text]Cl−, Br−,[Formula: see text] and [Formula: see text] at 25° [Formula: see text] and ionic strength I = 0.1 M LiClO4/HClO4, [Formula: see text] −10.6, −9.2, −6.3, and +16.8 cm3 mol−1, and x = 8.0, 4.1, 3.9, 1.9, and −4.2; for Xn− = NCS−, the mean ΔV* from P = 0.001 to 2.5 kbar at 88° is −4 cm3 mol−1. Detailed consideration of these data, especially their correlation with the molar volume of reaction by a straight line of unit slope for [Formula: see text] Cl−, Br−, NO3−, and H2O, provides strong evidence for a dissociative interchange mechanism. For [Formula: see text] the separating entity is probably HN3 rather than [Formula: see text] For Xn− = NCS−, aquation is incomplete, at practical complex concentrations; at 88.0°, 1 bar, and I = 0.1 M LiClO4/HClO4, k = 3.3 × 10−6 s−1 and the stability constant of Co(NH3)5NCS2+ is 490 M−1.

scholarly journals Studies on the Iron Nanoparticles Catalyzed Reduction of Substituted Aromatic Ketones to Alcohols

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
L. Parimala ◽  
J. Santhanalakshmi
Keyword(s):  
Iron Nanoparticles ◽  
Rate Coefficient ◽  
Catalytic Efficiency ◽  
Hydrogenation Reaction ◽  
Uv Spectra ◽  
Vinyl Pyrrolidone ◽  
Aromatic Ketones ◽  
First Order ◽  
Order Rate ◽  
Pseudo First Order

Iron nanoparticles are synthesized and size characterized using HRTEM, FESEM, and XRD. Polyethylene glycol(PEG), carboxymethyl cellulose (CMC), and poly N-vinyl pyrrolidone (PVP) are used as nanoparticle stabilizers. The sizes of Fe nps are found to be 9 nm, 14 nm, and 17 nm ± 1 nm corresponding to PEG, CMC, and PVP stabilizers, respectively. The three different iron nanoparticles (Fe nps) prepared are used as catalysts in the hydrogenation reaction of various substituted aromatic ketones to alcohols with NaBH4. The progress of the reaction was monitored using time variance UV spectra. Kinetic plots are made from the absorbance values and the pseudo first order rate coefficient values are determined. Catalytic efficiency of the Fe nps is obtained by comparing the pseudo first order rate coefficient values, times of reaction, and % yield. Fe-PEG nps was found to act as better catalyst than Fe-CMC nps and Fe-PVP nps. Also, effects of substituents in the aromatic ring of ketones reveal that +I substituents are better catalysed than –I substituents.

Die Kinetik des Zerfalls von tert. Butylperoxypivalat bei hohen Drücken und Temperaturen / The Kinetics of the Decomposition of tert.Butylperoxypivalate up to High Pressures and Temperatures

1981 ◽  
Vol 36 (12) ◽  
pp. 1371-1377 ◽  
Author(s):  
M. Buback ◽  
H. Lendle
Keyword(s):  
Activation Energy ◽  
High Pressure ◽  
High Pressures ◽  
Activation Volume ◽  
Rate Law ◽  
First Order ◽  
Order Rate ◽  
High Pressures And Temperatures ◽  
Kinetics Of

AbstractThe decomposition of tert. butylperoxypivalate dissolved in n-heptane has been measured ir-spectroscopically in optical high-pressure cells up to 2000 bar at temperatures between 65 °C and 105 °C. The reaction follows a first order rate law with an activation energy Ea = 122.3 ±3.0 kJ · mol-1 and an activation volume ⊿V≠ = 1.6 ± 1.0 cm3 mol-1 .

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