Oxidation of Olefins Representing Some Structural Units of GR-S

1952 ◽  
Vol 25 (1) ◽  
pp. 21-32 ◽  
Author(s):  
W. C. Warner ◽  
J. Reid Shelton
Keyword(s):  
Phenyl Group ◽  
Kinetic Mechanism ◽  
Oxidation Reactions ◽  
Chain Reaction ◽  
Instantaneous Rate ◽  
Initial Oxygen ◽  
Oxidation Of Olefins ◽  
A Minor ◽  
The Relationship ◽  
Kinetics Of

Abstract Three olefins were oxidized in the liquid phase with molecular oxygen to determine the kinetics of the oxidation reactions and the relationship to oxidation of rubber. The instantaneous rate of oxidation was found to be related to the analytically determined olefin and peroxide concentrations by the equation : Rate=k (unreacted olefin)(peroxide), where rate equals moles of oxygen per mole of original olefin per hour and the parentheses represent molarities. Presence of a phenyl group was found to affect k, but only in a minor way, indicating that the same fundamental kinetic mechanism applies in both aromatic and aliphatic olefins. The data are consistent with the general kinetic mechanism of Bolland involving oxygen attack at the alpha-methylenic group. However, it appears probable that initial oxygen attack can also occur at the double bond, resulting in the formation of a peroxide biradical, which may then react with other olefin molecules, initiating the usual chain reaction mechanism.

THE KINETICS OF THE OXIDATION OF GASEOUS ACETONE

1932 ◽  
Vol 6 (3) ◽  
pp. 265-279 ◽  
Author(s):  
E. W. R. Steacie
Keyword(s):  
Temperature Coefficient ◽  
Chain Length ◽  
Oxidation Reactions ◽  
Chain Reaction ◽  
Effect Of Pressure ◽  
Kinetics Of ◽  
Chain Type

The oxidation of gaseous acetone is a homogeneous chain reaction between 350° and 500 °C. The effect of pressure on the rate of the reaction indicates an "order" somewhat greater than three. The indications are that the first step in the reaction consists of the formation of an unstable peroxide. The predominant reaction then appears to be the formation of acetic and formic acids together with their products of oxidation and decomposition. The actual course of the reaction varies somewhat as the temperature changes.The temperature coefficient and the effects of surface and of foreign gases show that the chain length is comparatively short and varies with temperature. The process by which the chains are initiated is probably bimolecular. The reaction differs from most oxidation reactions of the chain type in that the concentrations of the two reactants are about equally important in so far as their effect on the rate of the reaction is concerned.

Infrared spectra and substituent effects in 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones

1983 ◽  
Vol 48 (2) ◽  
pp. 586-595 ◽  
Author(s):  
Alexander Perjéssy ◽  
Pavol Hrnčiar ◽  
Ján Šraga
Keyword(s):  
Substituent Effects ◽  
Phenyl Group ◽  
Wave Number ◽  
Vibrational Coupling ◽  
Wave Numbers ◽  
Stretching Vibration ◽  
Stretching Vibrations ◽  
The Relationship ◽  
Derivatives Of ◽  
Effect Of Structure

The wave numbers of the fundamental C=O and C=C stretching vibrations, as well as that of the first overtone of C=O stretching vibration of 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones and 1,3-cycloheptanedione were measured in tetrachloromethane and chloroform. The spectral data were correlated with σ+ constants of substituents attached to phenyl group and with wave number shifts of the C=O stretching vibration of substituted acetophenones. The slope of the linear dependence ν vs ν+ of the C=C stretching vibration of the ethylenic group was found to be more than two times higher than that of the analogous correlation of the C=O stretching vibration. Positive values of anharmonicity for asymmetric C=O stretching vibration can be considered as an evidence of the vibrational coupling in a cyclic 1,3-dicarbonyl system similarly, as with derivatives of 1,3-indanedione. The relationship between the wave numbers of the symmetric and asymmetric C=O stretching vibrations indicates that the effect of structure upon both vibrations is symmetric. The vibrational coupling in 1,3-cycloheptanediones and the application of Seth-Paul-Van-Duyse equation is discussed in relation to analogous results obtained for other cyclic 1,3-dicarbonyl compounds.

scholarly journals Solid-State Redox Kinetics of CeO2 in Two-Step Solar CH4 Partial Oxidation and Thermochemical CO2 Conversion

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 723
Author(s):  
Mahesh Muraleedharan Nair ◽  
Stéphane Abanades
Keyword(s):  
Solid State ◽  
Solar Energy ◽  
Kinetic Models ◽  
Oxygen Carrier ◽  
Co2 Conversion ◽  
Oxidation Reactions ◽  
Redox Kinetics ◽  
Concentrated Solar Energy ◽  
Ceria Reduction ◽  
Kinetics Of

The CeO2/CeO2−δ redox system occupies a unique position as an oxygen carrier in chemical looping processes for producing solar fuels, using concentrated solar energy. The two-step thermochemical ceria-based cycle for the production of synthesis gas from methane and solar energy, followed by CO2 splitting, was considered in this work. This topic concerns one of the emerging and most promising processes for the recycling and valorization of anthropogenic greenhouse gas emissions. The development of redox-active catalysts with enhanced efficiency for solar thermochemical fuel production and CO2 conversion is a highly demanding and challenging topic. The determination of redox reaction kinetics is crucial for process design and optimization. In this study, the solid-state redox kinetics of CeO2 in the two-step process with CH4 as the reducing agent and CO2 as the oxidizing agent was investigated in an original prototype solar thermogravimetric reactor equipped with a parabolic dish solar concentrator. In particular, the ceria reduction and re-oxidation reactions were carried out under isothermal conditions. Several solid-state kinetic models based on reaction order, nucleation, shrinking core, and diffusion were utilized for deducing the reaction mechanisms. It was observed that both ceria reduction with CH4 and re-oxidation with CO2 were best represented by a 2D nucleation and nuclei growth model under the applied conditions. The kinetic models exhibiting the best agreement with the experimental reaction data were used to estimate the kinetic parameters. The values of apparent activation energies (~80 kJ·mol−1 for reduction and ~10 kJ·mol−1 for re-oxidation) and pre-exponential factors (~2–9 s−1 for reduction and ~123–253 s−1 for re-oxidation) were obtained from the Arrhenius plots.

Gas phase interaction with catalytic oxidation reactions

1972 ◽  
Vol 326 (1565) ◽  
pp. 215-227 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Maleic Anhydride ◽  
Catalytic Oxidation ◽  
Gas Phase ◽  
Major Part ◽  
Oxidation Reactions ◽  
Mixed Gas ◽  
Kinetics Of ◽  
Oxidation Of Benzene ◽  
Homogeneous Decomposition

Studies of the catalytic oxidation of benzene to maleic anhydride and carbon dioxide over vanadia/molybdena catalysts show that the major part of the reaction involves interacting gas and gas-solid processes. The results are consistent with a mechanism in which a benzeneoxygen adduct is formed catalytically, desorbs and then reacts to give maleic anhydride entirely in the gas phase. On the basis of this proposed mechanism, the kinetics of individual reactions have been investigated in some depth. The over-oxidation of maleic anhydride has been found to be not significant under the conditions of reaction. The kinetic relationships governing the homogeneous decomposition of the adduct and the oxidation of the adduct to maleic anhydride and to carbon dioxide have been established. The results show that essentially all of the anhydride originates from mixed gas-solid/gas reaction while substantial amounts of carbon dioxide are produced entirely catalytically.

CORRELATION BETWEEN ELECTRIC CHARGING OF THE SAMPLE SURFACE AND KINETICS OF OPTICALLY STIMULATED EXOELECTRON EMISSION (OSEE) FROM CRYOSOLIDIFIED NaCl SOLUTION

1990 ◽  
Vol 04 (03) ◽  
pp. 201-209
Author(s):  
A. GIEROSZYŃSKI
Keyword(s):  
Electric Fields ◽  
Surface Potential ◽  
Surface Region ◽  
Sample Surface ◽  
Exoelectron Emission ◽  
Nacl Solution ◽  
Emitter Surface ◽  
Emitter Layer ◽  
The Relationship ◽  
Kinetics Of

It was found that OSEE kinetics from electron bombarded cryosolidified NaCl solution, depend on electric charging of the sample surface. It was shown that from the relationship between the maximum surface potential and the parameters of OSEE kinetic, intensities of electric fields in the emitter layer could be estimated. It is supposed that nonhomogeneous electric fields existing in the emitter surface region, influence the emission levels responsible for the course of OSEE kinetics.

Zebrafish embryos exposed to deltamethrin exhibit abnormalities despite induced expression of related genes (you, you-too, momo and u-boot)

2018 ◽  
Vol 35 (1) ◽  
pp. 11-19
Author(s):  
Kuder Reshma Shabnam ◽  
Dharmapuri Gangappa ◽  
Gundala Harold Philip
Keyword(s):  
Vital Role ◽  
Primary Objective ◽  
Chain Reaction ◽  
Environmental Persistence ◽  
Expression Of Genes ◽  
Pericardial Edema ◽  
Eye Pigmentation ◽  
Polymerase Chain ◽  
Relationship Of ◽  
The Relationship

Evaluation of the toxic effects of a widely used synthetic pyrethroid, deltamethrin (DM), was carried out in this study. This pesticide is preferred for pest control because of its low environmental persistence and toxicity. We investigated the expression pattern of four genes, namely, you ( you), yot ( you-too), momo ( mom) and ubo ( u-boot) during early development of zebrafish, that is, from 12 hpf to 48 hpf stages. These stages are selected as most of the important developmental aspects take place during this period. All four genes are known to play a vital role in development of notochord and somites. To understand the effect of DM on development, embryos of 4 hpf stage were exposed to two concentrations (100 and 200 µg/L) of DM, and observations were made at 12, 24 and 48 hpf stages. Our earlier studies have shown phenotypic abnormalities such as notochord bending, tail deformation, yolk sac and pericardial edema, lightening of body and eye pigmentation and interfered in somite patterning, during these stages of development. Understanding the relationship of phenotypic abnormalities with these four genes has been our primary objective. These four genes were analyzed by Reverse transcription (RT)-polymerase chain reaction and intensity of the bands has shown induction in their expression after exposure to the toxicant. In spite of the expression of genes, it was noticed that DM caused abnormalities. It can be said from the results that translational pathway could have been affected.

Na+-K+-ATPase-dependent sodium flux in cortical collecting tubule

1988 ◽  
Vol 255 (4) ◽  
pp. F605-F613 ◽  
Author(s):  
M. Blot-Chabaud ◽  
F. Jaisser ◽  
M. Gingold ◽  
J. P. Bonvalet ◽  
N. Farman
Keyword(s):  
Special Device ◽  
Instantaneous Rate ◽  
Sodium Flux ◽  
Na Efflux ◽  
Collecting Tubule ◽  
Pump Activity ◽  
Total Capacity ◽  
Collecting Tubules ◽  
Kinetics Of ◽  
Cortical Collecting Tubule

The instantaneous rate of efflux of intracellular Na was studied in rabbit isolated cortical collecting tubules (CCT) as a function of temperature and intracellular Na concentration ([Na]i). [Na]i of microdissected CCT was increased by cold and K-free exposure in the presence of 22Na and the extracellular tracer [3H] sorbitol. [Na]i rose rapidly to 40 mM at 30 min, after which it rose more slowly, reaching 120-140 mM at 6 h. Kinetics of Na efflux were studied after rapid rewarming, using a special device allowing measurements at 20-s intervals. Under control conditions, the total Na load was extruded in less than 8 min, whereas, in the presence of 10(-4) M ouabain, only 50% of the load was extruded during this period of time. Ouabain-sensitive Na efflux was first evident at 13 degrees C and gradually increased between 13 and 35 degrees C. At 37 degrees C, Na+-K+-ATPase-dependent Na efflux was dependent on [Na]i. This efflux gradually increased, from 0.05 to 0.5 peq.nl tubular volume-1.s-1 as a function of [Na]i and reached a plateau at 70 mM [Na]i. It is concluded that [Na]i is a major modulator of the pump activity in CCT; at normal levels of [Na]i, the pump is operating at only a small fraction of its total capacity.

scholarly journals The calculation of transcript flux ratios reveals single regulatory mechanisms capable of activation and repression

2018 ◽  
Vol 115 (50) ◽  
pp. E11604-E11613 ◽  
Author(s):  
Eric A. Galburt
Keyword(s):  
Rate Constants ◽  
Flux Ratio ◽  
Stringent Response ◽  
Kinetic Mechanism ◽  
Regulation Of Transcription ◽  
Sequence Motifs ◽  
Response Factors ◽  
Initiation Rate ◽  
Dna Sequence Motifs ◽  
Kinetics Of

The regulation of transcription allows cells to adjust the rate of RNA polymerases (RNAPs) initiated in a promoter-specific manner. Classically, transcription factors are directed to a subset of promoters via the recognition of DNA sequence motifs. However, a unique class of regulators is recruited directly through interactions with RNAP. Surprisingly, these factors may still possess promoter specificity, and it has been postulated that the same kinetic mechanism leads to different regulatory outcomes depending on a promoter’s basal rate constants. However, mechanistic studies of regulation typically report factor activity in terms of changes in the thermodynamics or kinetics of individual steps or states while qualitatively linking these observations to measured changes in transcript production. Here, I present online calculators that allow for the direct testing of mechanistic hypotheses by calculating the steady-state transcript flux in the presence and absence of a factor as a function of initiation rate constants. By evaluating how the flux ratio of a single kinetic mechanism varies across promoter space, quantitative insights into the potential of a mechanism to generate promoter-specific regulatory outcomes are obtained. Using these calculations, I predict that the mycobacterial transcription factor CarD is capable of repression in addition to its known role as an activator of ribosomal genes. In addition, a modification of the mechanism of the stringent response factors DksA/guanosine 5′-diphosphate 3′-diphosphate (ppGpp) is proposed based on their ability to differentially regulate transcription across promoter space. Overall, I conclude that a multifaceted kinetic mechanism is a requirement for differential regulation by this class of factors.

scholarly journals From Boondoggle to Settlement Colony: Hendrik Witbooi and the Evolution of Germany's Imperial Project in Southwest Africa, 1884–1894

2017 ◽  
Vol 50 (4) ◽  
pp. 449-470
Author(s):  
Adam A. Blackler
Keyword(s):  
Colonial History ◽  
German State ◽  
Imperial Authority ◽  
Military Violence ◽  
Commercial Enterprise ◽  
Important Extension ◽  
A Minor ◽  
The Relationship ◽  
Southwest Africa

AbstractIn the span of ten years, what started as a minor commercial enterprise in a faraway African territory grew into an important extension of the German state. This article reorients our understanding of the relationship between theKaiserreichand its overseas empire, specifically with a focus on Captain Hendrik Witbooi and on how the Witbooi Namaqua he led influenced the evolution of German imperial rule in Southwest Africa between 1884 and 1894. Witbooi's refusal to accept imperial authority compelled colonial officials to confront their administrative limitations in the colony. When the façade of imperial fantasy gave way to colonial reality, German administrators expanded the size and scope of the imperial government to subdue the Namaqua. The article emphasizes the appointments ofLandeshauptmannCurt von François and Governor Theodor Leutwein as critical examples of Witbooi's impact on imperial policy, as well as the colonial administration's embrace of military violence to attain German supremacy in Southwest Africa. An emphasis on the Witbooi Namaqua illustrates the prominent role of Africans in German colonial history and exposes how peoples in distant places like Windhoek and Otjimbingwe manipulated official efforts to control and exploit the colony.

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