Oxidation reactions in monolayers of long-chain unsaturated compounds

1956 ◽  
Vol 9 (3) ◽  
pp. 347 ◽  
Author(s):  
AR Gilby ◽  
AE Alexander
Keyword(s):  
Chain Length ◽  
Quantitative Measure ◽  
Oxidation Reactions ◽  
Time Curve ◽  
Unsaturated Compounds ◽  
Degree Of Unsaturation ◽  
Mixed Films ◽  
Reacting Systems ◽  
Kinetics Of ◽  
Long Chain

The kinetics of the oxidation of long-chain unsaturated compounds when spread as monolayers on KMnO4 solutions has been determined from measurements of the changes in area with time. The effects of number of double bonds (unconjugated),of chain length, and of permanganate concentration were studied, as well as the behaviour of the dihydroxy compounds believed to be the first stage of the oxidation process. The velocity constant has been found to increase markedly for each additional double bond, and to be independent of chain length, thus providing a quantitative measure of degree of unsaturation in unconjugated long-chain compounds. Mixed films of unsaturated and dihydroxy acids have been studied and the results used to allow for deviation from additivity of areas in the reacting systems. On this basis the overall area-time curve, which goes through a maximum, has been quantitatively accounted for.

Kinetics of the reaction of the hydrophobic ester 4-nitrophenyl decanoate with long-chain N-alkylimidazoles above and below their critical micelle concentration

1974 ◽  
Vol 27 (10) ◽  
pp. 2149 ◽  
Author(s):  
DG Oakenfull ◽  
DE Fenwick
Keyword(s):  
Critical Micelle Concentration ◽  
Chain Length ◽  
Mole Fraction ◽  
Rate Constants ◽  
Hydrophobic Interactions ◽  
Hydrocarbon Chain ◽  
Hydrocarbon Chain Length ◽  
Hydrocarbon Chains ◽  
Kinetics Of ◽  
Long Chain

The kinetics of the reaction of 4-nitrophenyl decanoate with a series of straight-chain N-alkylimidazoles have been studied at 25� in water and aqueous ethanol. In water, below the critical micelle concentration of the N-alkylimidazole, hydrophobic interaction between the hydrocarbon chains of the reactants caused substantial increases in the reaction rate (up to about 200-fold) compared with the rate of reaction of 4-nitrophenyl acetate with N-methylimidazole. The rate constants, though, differed from those previously reported which were measured with a higher initial concentration of ester. No increase in rate with increasing hydrocarbon chain length could be detected in the presence of a large concentration of ethanol (mole fraction of 0.31) but a rate increase did occur in the presence of a more moderate concentration of ethanol (mole fraction of 0.10), confirming that hydrophobic interactions persist in this mixed solvent. The long-chain ester reacts rapidly with N-alkylimidazole micelles. Association constants (K) for binding the ester to the micelles and rate constants for the reaction of the bound ester (km) were estimated by following the conventional treatment of the kinetics of micelle-catalysed reactions. The value of K was found to increase sharply with increasing hydrocarbon chain length of the micelle but km showed the opposite trend.

THE FERMENTATION OF LONG-CHAIN COMPOUNDS BY TORULOPSIS MAGNOLIAE: I. STRUCTURES OF THE HYDROXY FATTY ACIDS OBTAINED BY THE FERMENTATION OF FATTY ACIDS AND HYDROCARBONS

1962 ◽  
Vol 40 (7) ◽  
pp. 1326-1338 ◽  
Author(s):  
A. P. Tulloch ◽  
J. F. T. Spencer ◽  
P. A. J. Gorin
Keyword(s):  
Fatty Acids ◽  
Carbon Atom ◽  
Chain Length ◽  
Hydroxy Fatty Acid ◽  
Hydroxyl Group ◽  
Fatty Esters ◽  
Degree Of Unsaturation ◽  
Chain Compounds ◽  
Chain Lengths ◽  
Long Chain

The yield of extracellular glycolipid produced by Torulopsis magnoliae is increased three-to five-fold by the addition of suitable compounds to the growing culture. The supplement, which can be a long-chain acid, ester, hydrocarbon, or glyceride, is hydroxylated and converted to hydroxy fatty acid sophorosides. Fatty esters of all chain lengths from C16 to C22, including several unsaturated esters, and even-numbered hydrocarbons from C16 to C24 are readily fermented. Shorter-chain compounds are used poorly or not at all. With compounds of 16 to 18 carbon atoms, hydroxylation occurs at the terminal or penultimate carbon atom, depending on degree of unsaturation and chain length. Substrates of more than 18 carbon atoms are mainly reduced in chain length by one or more two-carbon units and hydroxylated, giving C17 or C18 acids with the hydroxyl group on the penultimate carbon atom. The various enzymic reactions which occur during the fermentation are discussed.

scholarly journals Acyl-chain specificity of human milk bile-salt-activated lipase

1991 ◽  
Vol 279 (1) ◽  
pp. 297-302 ◽  
Author(s):  
C S Wang
Keyword(s):  
Human Milk ◽  
Bile Salt ◽  
Chain Length ◽  
Acyl Chain ◽  
Fatty Acyl ◽  
Acyl Chain Length ◽  
Enzyme Substrate ◽  
Consistent Trend ◽  
Kinetics Of ◽  
Long Chain

In order to probe the active-site structure of human milk bile-salt-activated lipase (BAL), the kinetics of the BAL-catalysed reaction were studied using monoesters as substrates. Among the fatty acyl chains, ranging from C8 to C16 of monoacylglycerols in a single equimolar assay mixture, there was a consistent trend of increased reactivity with decreased fatty-acyl-chain length for both the basal and taurocholate-stimulated activities of BAL. In addition, the detection of hydrolysis of long-chain monoacylglycerols in the absence of bile salt indicates that it is possible for the long-chain fatty acid monoester to form an enzyme-substrate complex with the basal form of BAL. I further examined the reaction kinetics of BAL with water-soluble short-chain esters of p-nitrophenol. The results indicated that there is a consistent trend towards a decreased Michaelis-Menten constant with increased acyl-chain length. Therefore it was concluded that the decreased reactivity with increased acyl-chain length of acylglycerols is probably not a consequence of the lowered affinity of the substrate for the enzyme. The fact that butyrate ester has the optimum acyl chain to be a substrate of BAL can be attributed to its acyl-chain length being long enough for interaction with the active centre of BAL and short enough to provide adequate positioning of the ester bond for transition state complex formation. The calculated free energy of BAL catalysis based on the derived kinetic parameters provides additional insight into the effect on the enzyme-substrate interaction of increasing the number of methylene groups in the acyl chain of substrates.

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.

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.

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.

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