Reactions of alicyclic ketones in carbon tetrachloride. II. Kinetics of the chlorination of 2-chlorocyclopentanone and 2-chlorocyclohexanone, catalyzed by hydrogen chloride

1986 ◽  
Vol 64 (9) ◽  
pp. 1690-1696 ◽  
Author(s):  
Eize J. Stamhuis ◽  
Henk Maatman ◽  
Geert E. H. Joosten
Keyword(s):  
Carbon Tetrachloride ◽  
Hydrogen Chloride ◽  
Kinetic Equations ◽  
Base Catalysis ◽  
Strong Increase ◽  
Reaction Products ◽  
Reaction Models ◽  
Basic Catalysts ◽  
Self Association ◽  
Kinetics Of

The kinetics of the direct chlorination of 2-chlorocyclopentanone (2-mccp) and 2-chlorocyclohexanone (2-mcch) in carbon tetrachloride, catalyzed by hydrogen chloride, were studied. Reaction products are all the possible 2,2-, 2,5-, and 2,6-dichloro compounds. The ratios depend on the concentrations of the monochloro compound and hydrogen chloride. Surprisingly, even at conversions of the monochloro compound as low as 2%, 2,2,5-trichlorocyclopentanone and 2,2,6-trichlorocyclohexanone, respectively, are also formed. The chlorination reaction of both monochloro ketones shows zero order in chlorine. The order in hydrogen chloride is 1.3. The order in 2-mccp and 2-mcch varies somewhat with the concentration of the ketone and was found to be roughly 1.7. The variation in reaction order is explained by a partial self-association of the ketones. The ketones act as substrates as well as basic catalysts in the rate-determining α- or α′-carbon deprotonation. General base catalysis is clearly demonstrated by a strong increase in the rate of chlorination of 2-mccp upon addition of cyclopentanone (cp) to the reaction mixture, which agrees with the mechanism as presented in a previous paper. Kinetic equations derived from the reaction models for the "separate" and "mixed" ketone chlorinations accurately describe the observed rates of the chlorination of 2-mccp and 2-mcch in the concentration range of 0.04–1.0 M.

Reactions of alicyclic ketones in carbon tetrachloride. I, The kinetics of the chlorination of cyclopentanone and cyclohexanone catalyzed by hydrogen chloride

1986 ◽  
Vol 64 (9) ◽  
pp. 1681-1689 ◽  
Author(s):  
Eize J. Stamhuis ◽  
Henk Maatman ◽  
Henk Stinissen ◽  
Geert E. H. Joosten
Keyword(s):  
Carbon Tetrachloride ◽  
Hydrogen Chloride ◽  
Isotope Effects ◽  
Reaction Rates ◽  
Zero Order ◽  
Rate Determining Step ◽  
Conjugate Acid ◽  
Deuterium Isotope Effects ◽  
Self Association ◽  
Kinetics Of

The kinetics of the direct chlorination of cyclopentanone (cp) and cyclohexanone (ch) in carbon tetrachloride, catalyzed by hydrogen chloride, was studied. The rate of chlorination, measured by flow and stopped-flow techniques, is zero order in chlorine; the order in cp and ch increases from 1 at [cp] and [ch] of 0.01 M concentration to 2 at concentrations of 1 M. This is explained by self-association of the ketones in carbon tetrachloride solutions. The order in hydrogen chloride is 1. Since this compound is one of the products, the reaction is autocatalytic. Deuterium isotope effects and the kinetic data strongly point to a mechanism in which the oxygen-protonated monomeric ketone is α-carbon deprotonated in a rate-determining step. This step, which is catalyzed by the bases cp or ch, respectively, leads to the corresponding enol as intermediate. The enol is then chlorinated very rapidly. In addition to the chloro ketone, very reactive chloride anions are formed. A small fraction of these anions deprotonate α- or α′-carbon atoms of the oxygen-conjugate acid of the monochloro ketone. The remainder are captured by HCl to form energetically more favored Cl--(HCl)n complexes with n = 1, 2, or 3. This explains why, even at low conversions of the ketones, substantial amounts of the various dichloro isomers are formed in addition to monochloro products. A rate expression is derived, which excellently describes the experimentally obtained rates of chlorination of cp and ch over a range of reaction rates of more than three decades.

Kinetics of the catalytic hydrodesulphurization reaction system; hydrogenolysis of thiophene

1980 ◽  
Vol 45 (10) ◽  
pp. 2728-2741 ◽  
Author(s):  
Pavel Fott ◽  
Petr Schneider
Keyword(s):  
Atmospheric Pressure ◽  
Active Sites ◽  
Flow Reactor ◽  
Kinetic Equations ◽  
Reaction System ◽  
Reaction Products ◽  
Molybdenum Catalyst ◽  
Cobalt Molybdenum Catalyst ◽  
Kinetics Of ◽  
Reaction Schemes

Kinetics have been studied of the reaction system taking place during the reaction of thiophene on the cobalt-molybdenum catalyst in a gradientless circulation flow reactor at 360 °C and atmospheric pressure. Butane has been found present in a small amount in the reaction products even at very low conversion. In view of this, consecutive and parallel-consecutive (triangular) reaction schemes have been proposed. In the former scheme the appearance of butane is accounted for by rate of desorption of butene being comparable with the rate of its hydrogenation. According to the latter scheme part of the butane originates from thiophene via a different route than through hydrogenation of butene. Analysis of the kinetic data has revealed that the reaction of thiophene should be considered to take place on other active sites than that of butene. Kinetic equations derived on this assumption for the consecutive and the triangular reaction schemes correlate experimental data with acceptable accuracy.

Kinetics of Collision Processes in Dilute Noble Gases

2000 ◽  
Vol 65 (2) ◽  
pp. 141-160
Author(s):  
René Kalus
Keyword(s):  
Noble Gases ◽  
Kinetic Equations ◽  
Small Concentration ◽  
Stationary States ◽  
Dilute Gas ◽  
Reaction Models ◽  
Collision Processes ◽  
Quasiclassical Trajectories ◽  
Chemically Reacting ◽  
Kinetics Of

Kinetics of collision processes is analyzed for dilute noble gases within a linear approximation. Dilute gas is treated as a chemically reacting mixture of dimers and monomers. Two elementary reaction models are analyzed employing theoretical rate constants calculated recently from quasiclassical trajectories. Stability of stationary states and relaxation of small concentration perturbations are treated in terms of linearized kinetic equations. The results obtained are generalized for heavier noble gases (neon to xenon). Helium is, because of quantum nature, analyzed separately.

The Kinetics of Inhibition of the Action of Thrombin by the Fibrinopeptides Formed during the Clotting of Fibrinogen

1966 ◽  
Vol 16 (01/02) ◽  
pp. 277-295 ◽  
Author(s):  
A Silver ◽  
M Murray
Keyword(s):  
Amino Acids ◽  
Competitive Inhibition ◽  
Amorphous Material ◽  
Peptide Bond ◽  
Initial Reaction ◽  
Reaction Products ◽  
Coagulation Mechanism ◽  
Kinetics Of ◽  
Kinetics Of Inhibition ◽  
Burk Plot

SummaryVarious investigators have separated the coagulation products formed when fibrinogen is clotted with thrombin and identified fibrinopeptides A and B. Two other peaks are observed in the chromatogram of the products of coagulation, but these have mostly been dismissed by other workers. They have been identified by us as amino acids, smaller peptides and amorphous material (37). We have re-chromatographed these peaks and identified several amino acids. In a closed system of fibrinogen and thrombin, the only reaction products should be fibrin and peptide A and peptide B. This reasoning has come about because thrombin has been reported to be specific for the glycyl-arginyl peptide bond. It is suggested that thrombin also breaks other peptide linkages and the Peptide A and Peptide B are attacked by thrombin to yield proteolytic products. Thrombin is therefore probably not specific for the glycyl-arginyl bond but will react on other linkages as well.If the aforementioned is correct then the fibrinopeptides A and B would cause an inhibition with the coagulation mechanism itself. We have shown that an inhibition does occur. We suggest that there is an autoinhibition to the clotting mechanism that might be a control mechanism in the human body.The experiment was designed for coagulation to occur under controlled conditions of temperature and time. Purified reactants were used. We assembled an apparatus to record visually the speed of the initial reaction, the rate of the reaction, and the density of the final clot formed after a specific time.The figures we derived made available to us data whereby we could calculate and plot the information to show the mechanism and suggest that such an inhibition does exist and also further suggest that it might be competitive.In order to prove true competitive inhibition it is necessary to fulfill the criteria of the Lineweaver-Burk plot. This has been done. We have also satisfied other criteria of Dixon (29) and Bergman (31) that suggest true competitive inhibition.

The Kinetics of Glucose Decomposition with Sulfate Reduction in the Anaerobic Fluidized Bed Reactor

1993 ◽  
Vol 28 (2) ◽  
pp. 135-144 ◽  
Author(s):  
S. Matsui ◽  
R. Ikemoto Yamamoto ◽  
Y. Tsuchiya ◽  
B. Inanc
Keyword(s):  
Sulfate Reduction ◽  
Fluidized Bed ◽  
Kinetic Equations ◽  
Fluidized Bed Reactor ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Glucose Decomposition ◽  
Reaction Equations ◽  
Kinetics Of

Using a fluidized bed reactor, experiments on glucose decomposition with and without sulfate reduction were conducted. Glucose in the reactor was mainly decomposed into lactate and ethanol. Lactate was mainly decomposed into propionate and acetate, while ethanol was decomposed into propionate, acetate, and hydrogen. Sulfate reduction was not involved in the decomposition of glucose, lactate, and ethanol, but was related to propionate and acetate decomposition. The stepwise reactions were modeled using either a Monod expression or first order reaction kinetics in respect to the reactions. The coefficients of the kinetic equations were determined experimentally. The modified Monod and first order reaction equations were effective at predicting concentrations of glucose, lactate, ethanol, propionate, acetate, and sulfate along the beight of the reactor. With sulfate reduction, propionate was decomposed into acetate, while without sulfate reduction, accumulation of propionate was observed in the reactor. Sulfate reduction accelerated propionate conversion into acetate by decreasing the hydrogen concentration.

Carbon tetrachloride biodegradation in a fixed-biofilm reactor and its kinetic study

1998 ◽  
Vol 38 (8-9) ◽  
pp. 155-162 ◽  
Author(s):  
G. Jin ◽  
A. J. Englande
Keyword(s):  
Carbon Tetrachloride ◽  
Continuous Flow ◽  
Model Comparison ◽  
Biofilm Reactor ◽  
Pseudomonas Cepacia ◽  
Initial Concentration ◽  
Biphasic Model ◽  
Providencia Stuartii ◽  
Kinetics Of ◽  
Fixed Biofilm

Kinetics of Carbon Tetrachloride biodegradation are evaluated in a continuous-flow fixed-biofilm reactor with controlled initial redox potential. The column was seeded with a mixed culture of indigenous microorganisms Pseudomonas cepacia and Providencia stuartii. The fixed biofilm reactor exhibited 98%–99.9% biodegradation of CT introduced into the reactor at an initial concentration of about 200 μg/l for retention times of 1 to 4 days respectively. Four models were employed to evaluate the kinetics of CT biodegradation. These included: Eckenfelder (1989), Arvin (1991), Bouwer and McCarty (1985) and a biphasic model. Comparison of calculated results with observed results between these models agreed very closely to each other (0.968 < R2 < 0.999). Predicted performance was best described by the model of Bouwer and McCarty (1985). However, the biphasic and Eckenfelder models provided excellent correlations and were much simpler to apply. The biphasic model yielded very good correlations of the data for all detention times evaluated; whereas, the Eckenfelder model effected comparable results only at the longer retention times studied.

Kinetics of cyclization of S-ethoxycarbonylmethylisothiouronium chloride to 2-imino-4-thiazolidone

1979 ◽  
Vol 44 (3) ◽  
pp. 912-917 ◽  
Author(s):  
Vladimír Macháček ◽  
Said A. El-bahai ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrochloric Acid ◽  
Dilute Hydrochloric Acid ◽  
Base Catalysis ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of formation of 2-imino-4-thiazolidone from S-ethoxycarbonylmethylisothiouronium chloride has been studied in aqueous buffers and dilute hydrochloric acid. The reaction is subject to general base catalysis, the β value being 0.65. Its rate limiting step consists in acid-catalyzed splitting off of ethoxide ion from dipolar tetrahedral intermediate. At pH < 2 formation of this intermediate becomes rate-limiting; rate constant of its formation is 2 . 104 s-1.

Mechanism of hydration and isomerisation of 4-ethylidene-2,6-di-tert-butyl-2,5-cyclohexadien-1-one. Kinetics, acid-base catalysis and solvent deuterium isotope effects

1979 ◽  
Vol 44 (1) ◽  
pp. 110-122 ◽  
Author(s):  
Jiří Velek ◽  
Bohumír Koutek ◽  
Milan Souček
Keyword(s):  
Aqueous Medium ◽  
Rate Equation ◽  
Kinetic Data ◽  
Isotope Effects ◽  
Base Catalysis ◽  
Quinone Methide ◽  
Reaction Products ◽  
Acid Base ◽  
Deuterium Isotope Effects ◽  
Hydroxybenzyl Alcohol

Competitive hydration and isomerisation of the quinone methide I at 25 °C in an aqueous medium in the region of pH 2.4-13.0 was studied spectrophotometrically. The only reaction products in the studied range of pH are 4-hydroxybenzyl alcohol (II) and 4-hydroxystyrene (III). The form of the overall rate equation corresponds to a general acid-base catalysis. The mechanism of both reactions for three markedly separated pH regions is discussed on the basis of kinetic data and solvent deuterium effect.

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

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