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.

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.

scholarly journals OBSERVATIONS ON THROMBIN INACTIVATION BY HUMAN SERUM

1953 ◽  
Vol 37 (2) ◽  
pp. 139-156 ◽  
Author(s):  
Elemer Mihályi
Keyword(s):  
Serum Concentration ◽  
Human Serum ◽  
Toluidine Blue ◽  
Incubation Time ◽  
Energy Of Activation ◽  
Heat Inactivation ◽  
Clotting Time ◽  
Ph Optimum ◽  
First Order ◽  
First Order Kinetics

The inactivation of thrombin by serum follows a first order kinetics with thrombin concentrations of the order of 20 to 40 units per ml. of serum. With higher thrombin concentrations of 300 to 600 units per ml. of serum, the rate slows down and not the logarithm of the clotting time, but the clotting time itself increases proportionally with the incubation time. The antithrombic factor is stable at +4°C. for a period of 2 weeks, or for 3 months at –15°C. Heating over 58°C. destroys it rapidly. The heat inactivation has an energy of activation of 121,000 cal. With low thrombin concentrations the rate of thrombin inactivation increases linearly with increasing serum concentration. The pH optimum of the inactivation is at 8.5. Increasing the temperature increases the rate. The energy of activation of the thrombin destruction by serum is 14,000 cal. Heparin increases the rate considerably with low thrombin concentrations, but does not affect the rate with high thrombin concentrations. The effect of heparin can be abolished with protamine or toluidine blue. Some other reagents were also tested with respect to their effect upon the rate of inactivation of thrombin by serum.

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.

STUDIES ON HOMOGENEOUS FIRST ORDER GAS REACTIONS: IV. THE DECOMPOSITION OF PARA-n-BUTYRALDEHYDE AND PARA-ISOBUTYRALDEHYDE

1933 ◽  
Vol 9 (6) ◽  
pp. 603-609 ◽  
Author(s):  
C. C. Coffin
Keyword(s):  
Experimental Error ◽  
Degrees Of Freedom ◽  
Activation Energies ◽  
Energy Of Activation ◽  
Velocity Constant ◽  
First Order ◽  
Temperature Range ◽  
Measurable Rate ◽  
Gas Reactions ◽  
Internal Degrees Of Freedom

The gaseous decompositions of para-n-butyraldehyde and para-isobutyraldehyde to n-butyraldehyde and isobutyraldehyde respectively are homogeneous and first order over the pressure and temperature range investigated (1.3 to 55 cm. of mercury; 215 to 261 °C). Under these conditions the reactions go to completion at a measurable rate without complications. Within experimental error the activation energies of these reactions are equal and are approximately the same as that of the paracetaldehyde decomposition. This value is between 42,000 and 44,000 calories per mole. The rates of decomposition of the two parabutyraldehydes are very nearly the same at any temperature. At 500° abs. the velocity constant of the iso-compound is about 15% greater than that of the normal and about 100% greater than that of paracetaldehyde. The velocity constants at any temperature are given by the equations: para-n-butyraldehyde, [Formula: see text]; para-isobutyraldehyde, [Formula: see text]. The data are consistent with the idea that, for a series of reactions with the same energy of activation, an increase in the number of contributory internal degrees of freedom of a molecule will increase the probability of reaction.

Acetolysis of endo-5-Methyltricyclo-[2,2,1,02,6]hept-exo-3-yl and endo-5-Methyltricyclo[2,2,1,02,6]hept-endo-3-yl p-Bromobenzenesulfonates

1979 ◽  
Vol 32 (10) ◽  
pp. 2215 ◽  
Author(s):  
A Dell ◽  
BL Johnson
Keyword(s):  
Reaction Mechanism ◽  
Rate Constants ◽  
Ion Pair ◽  
Comparable Rate ◽  
First Order ◽  
First Order Kinetics

Acetolyses of the title compounds (4b) and (5b) at 25�7� proceed with steady first-order kinetics and with comparable rate constants. Some isomerization of (5b) to (4b) occurred during acetolysis of (5b). The products derived from acetolysis of each p-bromobenzenesulfonate were comparable and included endo-5-methyltricycl0[2,2,1,02,6]hept-exo-3-yl acetate (4c), endo-5-methyltricyclo- [2,2,1,02,6]hept-endo-3-yl acetate (5c), endo-3-methylbicyclo[2,2,1]hept-5-en-exo-2-yl acetate (6) and anti-7-methylbicyclo[2,2,1]hept-5-en-exo-2-yl acetate (7). These results are rationalized in terms of a reaction mechanism involving isomerization of the endo to the exo intimate ion pair, (10) to (ll), as well as a capturable intermediate carbocation which is common to the acetolysis of both p-bromo- benzenesulfonates.

The kinetic study of the addition of tetrachloromethane to styrene in the presence of copper complexes

1987 ◽  
Vol 52 (7) ◽  
pp. 1758-1763 ◽  
Author(s):  
Li Gwang Hun ◽  
Lubomír Nondek
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Kinetic Study ◽  
Copper Complexes ◽  
Catalytic Mechanism ◽  
First Order ◽  
First Order Kinetics ◽  
Experimental Activation Energy ◽  
Pseudo First Order ◽  
Kinetics Of

Kinetics of the addition of tetrachloromethane to styrene catalyzed by copper-amine complexes was studied. The pseudo-first order kinetics in respect to styrene and the catalyst was observed at an excess of tetrachloromethane. The reaction mechanism involving a catalytic cycle compatible with the kinetic observations is proposed. The experimental activation energy, being about 104 kJ mol-1, indicates a catalytic mechanism.

Re-examination of the kinetics of the thermal dehydroxylation of kaolinite

Clay Minerals ◽  
1984 ◽  
Vol 19 (4) ◽  
pp. 653-661 ◽  
Author(s):  
J. M. Criado ◽  
A. Ortega ◽  
C. Real ◽  
E. Torres De Torres
Keyword(s):  
Reaction Mechanism ◽  
Diffusion Process ◽  
Diffusion Mechanism ◽  
Activation Energies ◽  
First Order ◽  
First Order Kinetics ◽  
Comparison Of The Results ◽  
Kinetics Of

AbstractThe results obtained from this study of kaolinite dehydroxylation explain why different investigators have ascribed both first-order kinetics and a diffusion mechanism to this reaction. The fact that activation energies reported by these workers agree well, in spite of the different kinetics assumed when performing the calculations, is also explained. From a comparison of the results obtained by isothermal and non-isothermal methods it is concluded that, for reacted fractions,α, <0·6, kaolinite dehydroxylation is controlled by a diffusion process. A reaction mechanism explaining this behaviour is proposed.

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 &lt; 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.

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