scholarly journals THE THERMAL UNIMOLECULAR ISOMERIZATION OF 1,2-DICHLOROETHYLENE

1966 ◽  
Vol 44 (18) ◽  
pp. 2143-2148 ◽  
Author(s):  
L. D. Hawton ◽  
G. P. Semeluk
Keyword(s):  
Volume Ratio ◽  
No Decomposition ◽  
Radical Scavenger ◽  
Radical Chain ◽  
Limits Of Detection ◽  
First Order ◽  
First Order Kinetics ◽  
Trans Isomerization ◽  
Conversion Formula

The thermal cis–trans isomerization of 1,2-dichloroethylene in a toluene carrier was found to follow first order kinetics at temperatures below 846 °K. Within the limits of detection, no decomposition was observed, but there was evidence of a surface contribution to the isomerization. The results, extrapolated to a surface to volume ratio of zero, give for the cis to trans conversion[Formula: see text]and for the reverse action[Formula: see text]It is concluded that previous investigations which did not use a radical scavenger most probably were observations of a mixture of radical chain, heterogeneous, and unimolecular contributions to the isomerization.

The thermal decomposition of trimethylacetyl bromide

1970 ◽  
Vol 23 (3) ◽  
pp. 525 ◽  
Author(s):  
BS Lennon ◽  
VR Stimson
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Hydrogen Bromide ◽  
Transition States ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
Chain Mechanism ◽  
Radical Chain ◽  
First Order ◽  
Polar Transition

Trimethylacetyl bromide decomposes at 298-364� into isobutene, carbon monoxide, and hydrogen bromide in a first-order manner with rate given by k1 = 138 x 1014exp(-48920/RT) sec-1 The rate is unaffected by addition of the products or of inhibitors, or by increase of the surface/volume ratio of the reaction vessel. The likely radical chain mechanism is considered and rejected. The reaction is believed to be a molecular one, and possible cyclic and polar transition states are discussed.

Kinetics and mechanisms of the pyrolysis of diethyl ether I. The uninhibited reaction

1964 ◽  
Vol 278 (1375) ◽  
pp. 505-516 ◽  
Keyword(s):  
Diethyl Ether ◽  
Chain Process ◽  
Chain Mechanism ◽  
Radical Chain ◽  
Elementary Reactions ◽  
First Order ◽  
First Order Kinetics ◽  
Steady State Rate ◽  
State Rate ◽  
Radical Chain Process

The uninhibited thermal decomposition of diethyl ether was studied from 560 to 620 °C and at pressures ranging from 15 to 320 mmHg . The order of the overall reaction was between 1 and 3/2, the order being greater the higher the pressure. Analytical and kinetic data provide strong evidence that there is a molecular split of diethyl ether into ethanol and ethylene. The reaction leading to acetaldehyde and ethane, on the other hand, is concluded to be almost entirely a free-radical chain process. A detailed chain mechanism is postulated, involving first-order initiation and the reaction between C 2 H 5 and CH 2 CH 2 OC 2 H 5 as the chain-ending step. This mechanism is shown to give a steady-state rate equation which leads to first-order kinetics at lower ether pressures and three-halves-order kinetics at higher ones. The kinetic results lead to activation energies which are in satisfactory agreement with values calculated on the basis of the elementary reactions.

Thermal decomposition of citraconic anhydride

1971 ◽  
Vol 24 (4) ◽  
pp. 771 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
Gas Phase ◽  
Rate Constant ◽  
Arrhenius Equation ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
First Order ◽  
First Order Kinetics ◽  
Citraconic Anhydride

Citraconic anhydride decomposes in the gas phase over the range 440- 490� to give carbon dioxide, carbon monoxide, and propyne which undergoes some polymerization to trimethylbenzenes. The decomposition obeys first-order kinetics, and the Arrhenius equation ������������������� k1 = 1015.64 exp(-64233�500/RT) (s-1) describes the variation of rate constant with temperature. The rate constant is unaffected by the addition of isobutene or by increase in the surface/volume ratio of the reaction vessel. The reaction appears to be unimolecular and if a diradical intermediate is involved it may not be fully formed in the transition state.

Kinetics of neopentyl chloride pyrolysis. II. The radical-chain decomposition

1968 ◽  
Vol 46 (8) ◽  
pp. 1351-1359 ◽  
Author(s):  
J. S. Shapiro ◽  
E. S. Swinbourne
Keyword(s):  
Rate Coefficient ◽  
Surface Effect ◽  
High Surface ◽  
Volume Ratio ◽  
Unimolecular Decomposition ◽  
Radical Chain ◽  
Small Surface ◽  
First Order ◽  
Initiation Step ◽  
Kinetics Of

The radical-chain thermal decomposition of neopentyl chloride was studied in the temperature range of 410–496 °C and over the pressure range of 22 to 340 mm. A small surface effect was noted after prolonged conditioning of the vessel and in a vessel of high surface/volume ratio. The reaction is of three-halves order and the rate coefficient is expressible by k3/2 (11/2 mole−1/2 s−1) = 1013.55 ± 0.67 × e−56300 ± 2100/RT. The experimental facts are shown to be consistent with a mechanism involving chlorine atoms as the principal propagating radicals, with a first-order initiation step and a termination step involving the combination of methyl and chloromethyl radicals. The relative concentrations of the various radicals, calculated from known and estimated kinetic parameters, have been shown to be dependent on the hydrogen chloride produced from the concurrent unimolecular decomposition of neopentyl chloride reported in Part I. 1,1-Dimethylcyclopropane, found as a reaction product, is believed to be formed directly from neopentyl chloride by a radical-chain mechanism.

A formal [1,3] sigmatropic reaction involving free radical intermediates: a mechanistic investigation

1985 ◽  
Vol 63 (3) ◽  
pp. 745-754
Author(s):  
Gordon S. Bates ◽  
S. Ramaswamy
Keyword(s):  
Free Radical ◽  
Solvent Effect ◽  
Specific Mechanism ◽  
Radical Chain ◽  
First Order ◽  
Radical Intermediates ◽  
First Order Kinetics ◽  
Sigmatropic Shift ◽  
Mechanistic Investigation ◽  
Related Compounds

The quantitative isomerization of 2,2-bis(ethylthio)-3,3-dimethylpent-4-enal to 2,2-bis(ethylthio)-5-methylhex-4-enal was studied over the temperature range 130–170 °C. An investigation of the generality and specific mechanism of this formal [1,3] sigmatropic shift was conducted with six related compounds. The rearrangements were found to obey first-order kinetics, and on the basis of significant positive entropies of activation (52–106 J deg−1 mo−1), crossover and trapping experiments, and the lack of a solvent effect (decane vs. DMF), an intermolecular, free-radical chain pathway has been proposed for the isomerization. During the rearrangement of several of the compounds esr signals were observed that were consistent with the presence of the proposed free-radical intermediates. These esr signals have been computer simulated.

Photo-catalytic degradation of gaseous pollutants in paper mills of southern China

TAPPI Journal ◽  
2018 ◽  
Vol 17 (03) ◽  
pp. 167-178 ◽  
Author(s):  
Xin Tong ◽  
Jiao Li ◽  
Jun Ma ◽  
Xiaoquan Chen ◽  
Wenhao Shen
Keyword(s):  
Degradation Rate ◽  
Southern China ◽  
Catalytic Degradation ◽  
Pulp And Paper ◽  
Gaseous Pollutants ◽  
Pulp And Paper Mills ◽  
Paper Mills ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics

Studies were undertaken to evaluate gaseous pollutants in workplace air within pulp and paper mills and to consider the effectiveness of photo-catalytic treatment of this air. Ambient air at 30 sampling sites in five pulp and paper mills of southern China were sampled and analyzed. The results revealed that formaldehyde and various benzene-based molecules were the main gaseous pollutants at these five mills. A photo-catalytic reactor system with titanium dioxide (TiO2) was developed and evaluated for degradation of formaldehyde, benzene and their mixtures. The experimental results demonstrated that both formaldehyde and benzene in their pure forms could be completely photo-catalytic degraded, though the degradation of benzene was much more difficult than that for formaldehyde. Study of the photo-catalytic degradation kinetics revealed that the degradation rate of formaldehyde increased with initial concentration fitting a first-order kinetics reaction. In contrast, the degradation rate of benzene had no relationship with initial concentration and degradation did not conform to first-order kinetics. The photo-catalytic degradation of formaldehyde-benzene mixtures indicated that formaldehyde behaved differently than when treated in its pure form. The degradation time was two times longer and the kinetics did not reflect a first-order reaction. The degradation of benzene was similar in both pure form and when mixed with formaldehyde.

Kinetic of oxidation of methyl orange by vanadium(V) under conditions VO2+ and decavanadates coexist: Catalysis by Triton X-100 micellar medium

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Methyl Orange ◽  
Solution Ph ◽  
Vanadium Concentration ◽  
Limiting Behavior ◽  
First Order ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetic Pattern ◽  
Triton X ◽  
Kinetics Of

The kinetics of oxidation of methyl orange by vanadium(V) {V(V)} has been investigated in the pH range 2.3-3.79. In this pH range V(V) exists both in the form of decavanadates and VO2+. The kinetic results are distinctly different from the results obtained for the same reaction in highly acidic solution (pH < 1) where V(V) exists only in the form of VO2+. The reaction obeys first order kinetics with respect to methyl orange but the rate has very little dependence on total vanadium concentration. The reaction is accelerated by H+ ion but the dependence of rate on [H+] is less than that corresponding to first order dependence. The equilibrium between decavanadates and VO2+ explains the different kinetic pattern observed in this pH range. The reaction is markedly accelerated by Triton X-100 micelles. The rate-[surfactant] profile shows a limiting behavior indicative of a unimolecular pathway in the micellar pseudophase.

Biodegradation rates of aromatic contaminants in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Jean-Pierre Arcangeli ◽  
Erik Arvin
Keyword(s):  
Aromatic Hydrocarbons ◽  
Competitive Inhibition ◽  
Removal Rate ◽  
First Order ◽  
Biofilm Reactors ◽  
First Order Kinetics ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Degradation Rates ◽  
Order Surface

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

In-vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

2020 ◽  
Vol 16 ◽  
Author(s):  
M. Alarjah
Keyword(s):  
Half Life ◽  
Hplc Method ◽  
Hydrolysis Rate ◽  
First Order ◽  
First Order Kinetics ◽  
Rp Hplc ◽  
Pharmacokinetic Properties ◽  
Pseudo First Order ◽  
Kinetic Hydrolysis

Background: Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole. Objective: In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method. Method: Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC. Results: The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively. Conclusion: The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.

scholarly journals Influence of the Porosity of Polymer Foams on the Performances of Capacitive Flexible Pressure Sensors

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 1968 ◽  
Author(s):  
Sylvie Bilent ◽  
Thi Hong Nhung Dinh ◽  
Emile Martincic ◽  
Pierre-Yves Joubert
Keyword(s):  
Experimental Data ◽  
Linear Model ◽  
Dielectric Material ◽  
Pressure Sensors ◽  
Volume Ratio ◽  
Measurement Range ◽  
Polymer Foams ◽  
First Order ◽  
Non Linear ◽  
Flexible Pressure Sensors

This paper reports on the study of microporous polydimethylsiloxane (PDMS) foams as a highly deformable dielectric material used in the composition of flexible capacitive pressure sensors dedicated to wearable use. A fabrication process allowing the porosity of the foams to be adjusted was proposed and the fabricated foams were characterized. Then, elementary capacitive pressure sensors (15 × 15 mm2 square shaped electrodes) were elaborated with fabricated foams (5 mm or 10 mm thick) and were electromechanically characterized. Since the sensor responses under load are strongly non-linear, a behavioral non-linear model (first order exponential) was proposed, adjusted to the experimental data, and used to objectively estimate the sensor performances in terms of sensitivity and measurement range. The main conclusions of this study are that the porosity of the PDMS foams can be adjusted through the sugar:PDMS volume ratio and the size of sugar crystals used to fabricate the foams. Additionally, the porosity of the foams significantly modified the sensor performances. Indeed, compared to bulk PDMS sensors of the same size, the sensitivity of porous PDMS sensors could be multiplied by a factor up to 100 (the sensitivity is 0.14 %.kPa−1 for a bulk PDMS sensor and up to 13.7 %.kPa−1 for a porous PDMS sensor of the same dimensions), while the measurement range was reduced from a factor of 2 to 3 (from 594 kPa for a bulk PDMS sensor down to between 255 and 177 kPa for a PDMS foam sensor of the same dimensions, according to the porosity). This study opens the way to the design and fabrication of wearable flexible pressure sensors with adjustable performances through the control of the porosity of the fabricated PDMS foams.

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