A thermal [1,3] sigmatropic rearrangement: thermolysis of 2,2-bis(ethylthio)-3,3-dimethyl-4-pentenal

1981 ◽  
Vol 59 (21) ◽  
pp. 3120-3122 ◽  
Author(s):  
Gordon S. Bates ◽  
S. Ramaswamy
Keyword(s):  
Solvent Effect ◽  
Wide Temperature Range ◽  
Sigmatropic Rearrangement ◽  
Positive Entropy ◽  
First Order ◽  
Temperature Range ◽  
First Order Kinetics ◽  
Sigmatropic Shift ◽  
Entropy Of Activation

2,2-Bis(ethylthio)-3,3-dimethyl-4-pentenal was found to quantitatively isomerize to 2,2-bis(ethylthio)-5-methyl-4-hexenal over a wide temperature range (130–170 °C). This rearrangement can formally be regarded as a [1,3] sigmatropic shift. The reaction, which could be conveniently monitored by 1Hmr spectroscopy, was found to obey first order kinetics. The substantial positive entropy of activation (+ 61.5 J deg−1 mol−1) for the reaction and the negligible solvent effect (decane vs. DMF) are both consistent with a proposed diradical pathway.

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.

Study on Thermal Hysteresis of Elastic Modulus in Granular Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O

1990 ◽  
Vol 195 ◽  
Author(s):  
Yening Wang ◽  
Linhai Sun ◽  
Jin Wu ◽  
Min Gu
Keyword(s):  
Elastic Modulus ◽  
Single Crystal ◽  
Pore Size ◽  
Wide Temperature Range ◽  
Thermal Hysteresis ◽  
Coarse Grained ◽  
First Order ◽  
Temperature Range

ABSTRACTA large thermal hysteresis ( > 100 K) of elastic modulus was measured for coarse grained Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O. Whereas, only a small thermal hysteresis (2∼3 K) near the velocity minima at 240 K, and 150 K was observed in Bi2 Sr2 CaCu2 O8 single crystal, which were found to be associated with phaselike transitions (PLT). The investigations of isothermal recovery of modulus for coarse grained YBCO and BSCCO disclose that the large thermal hysteresis may be attributed to the defects of pore size generated in the interconnecting region between grains as a result of PLT of weak first order but covering a wide temperature range. The mechanism of a large thermal hysteresis for coarse grained samples has been discussed in detail.

scholarly journals A Fast, Inexpensive, and Safe Method for Residue Analysis of Meptyldinocap in Different Fruits by Liquid Chromatography/Tandem Mass Spectrometry

2010 ◽  
Vol 93 (6) ◽  
pp. 1957-1964 ◽  
Author(s):  
Kaushik Banerjee ◽  
Soma Dasgupta ◽  
Manjusha R Jadhav ◽  
Dattatraya G Naik ◽  
Axel Patrick Ligon ◽  
...  
Keyword(s):  
Ethyl Acetate ◽  
Residue Analysis ◽  
First Order ◽  
First Order Kinetics ◽  
Free Energy Of Activation ◽  
Subsequent Hydrolysis ◽  
Liquid Chromatography Tandem Mass ◽  
Rate Kinetics ◽  
Entropy Of Activation ◽  
Hydrolysis Of

Abstract An analytical method is reported for residue analysis of the fungicide meptyldinocap in different fruit matrixes that involves extraction with ethyl acetate, hydrolysis of the residues with ethanolamine, and determination by LC/MS/MS. The method involves extraction of 10 g sample with 10 mL ethyl acetate; evaporation of the ethyl acetate phase to dryness, and subsequent hydrolysis of the residues to 4,6-dinitro-2-(1-methylheptyl) phenol on reaction with 1 ethanolamine. The pH of this hydrolyzed product was neutralized with formic acid and analyzed by LC/MS/MS. The hydrolysis reaction followed pseudo-first-order kinetics, and the reaction product was spectroscopically confirmed as 2-(1-methylheptyl)-4,6-dinitrophenol. The method offered >80 recoveries at an LOQ of 10 ng/g for grape and mango, 25 ng/g for pomegranate with intralaboratory Horwitz ratio <0.5, and measurement uncertainties <10 at LOQ levels. Considering first-order rate kinetics, activation energy, enthalpy of activation, and entropy of activation varied as solvent > mango > grape > pomegranate. Free energy of activation at 298 K was higher than at 280 K and was similar for solvent and three matrixes at both temperatures.

Thermolysis of 5,5-dimethyl-4-aryl-Δ1-1,2,4-triazolin-3-ones in solution. Products, kinetics, substituent effects, and solvent effects

1981 ◽  
Vol 59 (1) ◽  
pp. 100-105 ◽  
Author(s):  
Lubomira M. Cabelkova-Taguchi ◽  
John Warkentin
Keyword(s):  
Transition State ◽  
Solvent Effects ◽  
Charge Separation ◽  
Substituent Effects ◽  
Activation Parameters ◽  
Oxidative Cyclization ◽  
First Order ◽  
Temperature Range ◽  
Aryl Amine ◽  
First Order Kinetics

A series of 5,5-dimethyl-4-aryl-Δ1-1,2,4-triazolin-3-ones (Ar = C6H5, p-C6H4CH3, p-C6H4OCH3, p-C6H4Cl, and p-C6H4Br) were prepared from the corresponding 4-arylsemicarbazones of acetone by oxidative cyclization on alumina. The triazolinones decompose in solution to N2, CO, and isopropylidene aryl amine, with first order kinetics, in the temperature range 148–200 °C. Average activation parameters are ΔH≠ = 35 kcal mol−1 and ΔS≠ = 8 cal K−1 mol−1. Substituent effects are correlated through σ-constants but the thermolyses are relatively insensitive to substituents, with ρ = −0.17 at 172.5 °C. Solvent effects indicate a transition state that is less polar than the ground state.It is tentatively concluded that the triazolinone fragmentation, like the analogous thermolysis of a Δ3-1,3,4-oxadiazolin-2-one, may be a fully-concerted but nonsynchronous process with a transition state involving little, if any, charge separation. Other mechanisms, except for those involving highly polar (e.g. zwitterionic) transition states, have not been ruled out.

Allene–methylacetylene isomerization over silica-supported cobalt and iron catalysts

1978 ◽  
Vol 56 (22) ◽  
pp. 2791-2796 ◽  
Author(s):  
C. P. Khulbe ◽  
R. S. Mann
Keyword(s):  
Reaction Mechanism ◽  
Active Sites ◽  
Iron Catalyst ◽  
Product Distribution ◽  
Energy Of Activation ◽  
Iron Catalysts ◽  
First Order ◽  
Temperature Range ◽  
Initial Reactant ◽  
First Order Kinetics

Equilibrium between allene and methylacetylene was studied over iron catalyst in the temperature range of 165 to 200 °C, with allene or methylacetylene as the initial reactant. In both cases similar equilibrium product-distribution (allene 16% and methylacetylene 84%), fairly close to the calculated value, is observed.Kinetics of allene-methylacetylene isomerization was studied between 70 and 165 °C. The order of reaction was always one and temperature independent. Both activity and calculated energy of activation (11.8 and 11.2 kcal/mol over iron and cobalt respectively) were similar for the two catalysts, suggesting that active sites for the reaction were also similar. This similarity, as well as the first order kinetics, are fully explained by a reaction mechanism based on adsorbate migration.

Entropy-Controlled Cu(II)-Catalyzed Oxidation of N-Acetyl-L-Cysteine by Methylene Blue in Acidic Medium

2017 ◽  
Vol 231 (6) ◽  
Author(s):  
Ranjana Sharma ◽  
Mahender Pal ◽  
K.K. Mishra
Keyword(s):  
Methylene Blue ◽  
Acidic Medium ◽  
Hydrogen Ions ◽  
First Order ◽  
First Order Kinetics ◽  
Rate Of Reaction ◽  
Entropy Of Activation ◽  
Size And Morphology ◽  
Kinetics Of ◽  
Catalyzed Oxidation

AbstractKinetics of the oxidation of N-acetyl-L-cysteine (NAC) by methylene blue (MB) catalyzed by Cu(II) have been investigated in presence of HCl. The reaction follows a first order kinetics in MB while the concentration order in NAC is zero. Hydrogen ions retard the rate of reaction. The reaction involves the participation of nanoparticles as revealed by SEM, XRD and FTIR techniques and a gel-like Cu-NAC network acts like the effective catalyst. The reaction conforms to Eley-Rideal mechanism at lower [NAC] while at higher [NAC], the kinetics are explained by extended Eley-Rideal mechanism. The reaction is regulated by the size and morphology of the nanoparticles and is controlled by the entropy of activation.

Fibre-optic temperature sensor with wide temperature range characteristics

1987 ◽  
Vol 134 (5) ◽  
pp. 291 ◽  
Author(s):  
K.T.V. Grattan ◽  
J.D. Manwell ◽  
S.M.L. Sim ◽  
C.A. Willson
Keyword(s):  
Wide Temperature Range ◽  
Temperature Sensor ◽  
Fibre Optic ◽  
Temperature Range

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.

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