Kinetics of individual steps in reaction network ethanol-diethyl ether-ethylene-water on alumina

1986 ◽  
Vol 51 (4) ◽  
pp. 763-773 ◽  
Author(s):  
Vladimír Morávek ◽  
Miloš Kraus
Keyword(s):  
Diethyl Ether ◽  
Reaction Network ◽  
Reaction Rates ◽  
Rate Equations ◽  
Initial Reaction ◽  
Ethanol Dehydration ◽  
Partial Pressures ◽  
Type Rate ◽  
Kinetics Of ◽  
Hydrolysis Of

The rates of single reactions have been measured at 250 °C in the complex reaction of ethanol dehydration to ethylene and to diethyl ether involving also hydrolysis of the ether, its disproportionation to ethanol and ethylene and its dehydration to ethylene. The found dependences of the initial reaction rates on partial pressures of the reactants were correlated by semiempirical Langmuir-Hinshelwood type rate equations.

KINETIC STUDIES ON THE HYDROLYSIS OF BENZOYLCHOLINE BY HUMAN SERUM CHOLINESTERASE

1956 ◽  
Vol 34 (1) ◽  
pp. 637-653 ◽  
Author(s):  
W. Kalow ◽  
K. Genest ◽  
N. Staron
Keyword(s):  
Kinetic Studies ◽  
Reaction Rates ◽  
Serum Cholinesterase ◽  
Initial Reaction ◽  
Ultraviolet Spectrophotometry ◽  
First Order ◽  
Low Concentrations ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Concentrations

Benzoylcholine stands out from other known substrates of serum cholinesterase because of its high apparent affinity for this enzyme combined with a rapid rate of destruction. The reaction kinetics of the hydrolysis of benzoylcholine can be studied by ultraviolet spectrophotometry, since the absorbance decreases in proportion to the concentration of substrate. Kinetic data obtained by measuring initial reaction rates, and by analyzing continuous hydrolysis curves, are the same within the range of experimental error. The enzymatic data are compatible with the assumption that in the presence of high substrate concentrations a complex consisting of esterase and two substrate molecules is formed. This complex is hydrolyzed more slowly than the complex containing one molecule of substrate which is formed at low concentrations of benzoylcholine. Alkaline hydrolysis of benzoylcholine follows the kinetics of a first order reaction.

KINETIC STUDIES ON THE HYDROLYSIS OF BENZOYLCHOLINE BY HUMAN SERUM CHOLINESTERASE

1956 ◽  
Vol 34 (3) ◽  
pp. 637-653 ◽  
Author(s):  
W. Kalow ◽  
K. Genest ◽  
N. Staron
Keyword(s):  
Kinetic Studies ◽  
Reaction Rates ◽  
Serum Cholinesterase ◽  
Initial Reaction ◽  
Ultraviolet Spectrophotometry ◽  
First Order ◽  
Low Concentrations ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Concentrations

Benzoylcholine stands out from other known substrates of serum cholinesterase because of its high apparent affinity for this enzyme combined with a rapid rate of destruction. The reaction kinetics of the hydrolysis of benzoylcholine can be studied by ultraviolet spectrophotometry, since the absorbance decreases in proportion to the concentration of substrate. Kinetic data obtained by measuring initial reaction rates, and by analyzing continuous hydrolysis curves, are the same within the range of experimental error. The enzymatic data are compatible with the assumption that in the presence of high substrate concentrations a complex consisting of esterase and two substrate molecules is formed. This complex is hydrolyzed more slowly than the complex containing one molecule of substrate which is formed at low concentrations of benzoylcholine. Alkaline hydrolysis of benzoylcholine follows the kinetics of a first order reaction.

Kinetics of hydrosilylation of tert-butylphenylketone by diphenylsilane catalysed by [Rh(1,5-COD)(-)-DIOP]+ClO-4

1980 ◽  
Vol 45 (8) ◽  
pp. 2224-2239 ◽  
Author(s):  
Ivan Kolb ◽  
Jiří Hetflejš
Keyword(s):  
Activation Parameters ◽  
Reaction Rates ◽  
Reaction Model ◽  
Initial Reaction ◽  
Title Reaction ◽  
Rate Determining Step ◽  
Kinetic Isotope ◽  
Arene Complex ◽  
Kinetics Of

Kinetic analysis of the title reaction has been made by the method of initial reaction rates. On the basis of the rate data, kinetic isotope effect and spectroscopic study of the reaction of the organosilicon hydride with the catalyst, the reaction model was proposed involving the following steps: the displacement of the diene by reaction with the silicon hydride from a rhodium-arene complex in an induction period of the hydrosilylation, the oxidative addition of the organosilicon hydride to the rhodium-arene complex, followed by the interaction of the ketone with the silylhydridorhodium (III) species in the rate determining step. The process is characterized by the following activation parameters: ΔU = 54.5 ± 8.5 kJ mol-1 and ΔS = -88± 25 J mol-1.K-1. The significant role of the entropic factor was supported by the analysis of the temperature dependence of the asymmetric efficiency of the catalyst.

Enantioselective hydrosilylation of tert-butyl phenyl ketone by diphenylsilane catalysed by [Rh{(-)-DIOP}2]+ClO4-

1980 ◽  
Vol 45 (10) ◽  
pp. 2808-2816 ◽  
Author(s):  
Ivan Kolb ◽  
Jiří Hetflejš
Keyword(s):  
Reaction Rates ◽  
Reaction Model ◽  
Rhodium Complex ◽  
Initial Reaction ◽  
Chiral Ligand ◽  
Title Reaction ◽  
First Order ◽  
Rate Determining Step ◽  
Phenyl Ketone ◽  
Kinetics Of

Kinetics of the title reaction has been studied by the method of initial reaction rates. In the presence of free chiral ligand the hydrosilylation was found to be first order in the catalyst and in the ketone and fractional order in the organosilicon hydride. The rate data and the results of spectroscopic study of interaction of diphenylsilane with the rhodium complex have been interpreted in terms of a reaction model involving formation of the corresponding cationic silyl(hydrido)rhodium complex followed by interaction of the ketone with this complex in the rate determining step. The results are confronted with those obtained for the analogous reaction catalysed by [Rh(1,5-COD)(-)-DIOP]+ClO4-.

KINETICS OF THE ENZYMATIC HYDROLYSIS OF SARIN

1956 ◽  
Vol 34 (1) ◽  
pp. 80-82 ◽  
Author(s):  
P. A. Adie ◽  
F. C. G. Hoskin ◽  
G. S. Trick
Keyword(s):  
Enzymatic Hydrolysis ◽  
Reaction Rates ◽  
Order Reaction ◽  
First Order Reaction ◽  
Optical Isomers ◽  
First Order ◽  
Kinetics Of ◽  
Hydrolysis Of

The enzymatic hydrolysis of sarin is apparently a single first-order reaction. There is no evidence of different reaction rates for the two possible optical isomers of sarin. During both the enzymatic and the non-enzymatic hydrolyses, sarin appears to be detoxified somewhat more rapidly than the manometric results would indicate. However, the detoxification parallels the manometric results sufficiently to stand in contrast to results obtained using tabun.

KINETICS OF THE CUPRIC ACETATE CATALYZED HYDROGENATION OF DICHROMATE IN AQUEOUS SOLUTION

1955 ◽  
Vol 33 (2) ◽  
pp. 356-364 ◽  
Author(s):  
E. Peters ◽  
J. Halpern
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Partial Pressure ◽  
Kinetic Study ◽  
Reaction Rates ◽  
Homogeneous Catalyst ◽  
Cupric Acetate ◽  
Partial Pressures ◽  
Kinetics Of

In aqueous solution, cupric acetate was found to act as a homogeneous catalyst for the reduction of dichromate by hydrogen, i.e.[Formula: see text] The paper describes a kinetic study of this reaction. Rates were determined at temperatures between 80° and 140 °C. and hydrogen partial pressures up to 27 atmospheres. The rate is independent of the dichromate concentration but varies directly with the partial pressure of hydrogen and is nearly proportional to the concentration of cupric acetate. The activation energy is 24,600 calories per mole. Cupric acetate, apparently acting as a true catalyst, activates the hydrogen through formation of a complex with it. An extension of the mechanism proposed earlier for the reaction of cupric acetate itself with hydrogen also accounts for the kinetics of the dichromate reaction.

Complexes of Nickel(II) and Copper(II) With 5,5,7-Trimethyl-1,4-Diazepane. Preparation and Kinetics of Acid-Hydrolysis

1986 ◽  
Vol 39 (2) ◽  
pp. 239 ◽  
Author(s):  
NF Curtis
Keyword(s):  
Acid Hydrolysis ◽  
Acid Concentration ◽  
Reaction Rates ◽  
Borohydride Reduction ◽  
Kinetics Of Hydrolysis ◽  
Rapid Reaction ◽  
Kinetics Of ◽  
Hydrolysis Of

The cyclic diamine 5,5,7-trimethyl-1,4-diazepane, tmdz, is formed by borohydride reduction of 5,7,7-trimethyl-2,3,6,7-tetrahydro-1H-1,4- diazepine , which is formed by a rapid reaction between ethanediamine and 4-methylpent-3-en-2-one. Salts of the cations [Ni( tmdz )2]2+ and [Cu( tmdz )2]2+ were prepared, and their properties are reported. The kinetics of hydrolysis of [Ni( tmdz )2]2+ and [Cu( tmdz )2]2+ and bis (1,4- diazepane )nickel(II), [Ni( dach )2]2+, in aqueous HCl/NaCl media have been studied. Reaction rates are independent of acid concentration over the ranges used . Ni2+,0.1-1 mol l-1 H+ in 1 mol l-1 Cl -, kobs(25°C) = 9.1(1)×10-7 s-1, kobs(50°C) = 2.0(1)×10-5 s-1,ΔH‡96(2)kJ mol-1,0.08-4 mol l-1, H+ in 4 mol l-1 Cl -, kobs (25°pC) = 2.0(3)°10-7 s-1. Cu2+, 0.04-1 mol l-1 H+, 1 mol l-1 Cl -, kobs (25°C) = 0.028(2) s-1, for the displacement of the second ligand . [Ni( dach )2]2+, 0.1-1 mol l-1 H+, 1 mol l-1 Cl -, kobs (25°C) = 0.051(2) s-1. [Ni( tmdz )2]2+ reacts more rapidly with NaOH/edta : 1 mol l-1 NaOH , 0.1 mol l-1, Na2(edtaH2), kobs (25°C) = 7.3(3)×10-3 s-1, 0.5 mol l-1 NaOH , 0.1 mol l-1 Na2(edtaH2), kobs (25°C) = 4.5(3)×10-3 s-1.

scholarly journals Estimation of gene reiteration from hybridization kinetics in moderate deoxyribonucleic acid excess

1977 ◽  
Vol 165 (1) ◽  
pp. 19-25 ◽  
Author(s):  
M Muto
Keyword(s):  
Deoxyribonucleic Acid ◽  
Theoretical Calculations ◽  
Reaction Rates ◽  
Initial Reaction ◽  
28S Rrna ◽  
Simple Method ◽  
Cdna Hybridization ◽  
Kinetics Of ◽  
Hybridization Reaction ◽  
Mouse Myeloma

Theoretical calculations were carried out to clarify how the DNA/RNA or the DNA/cDNA (complementary DNA) ratio in the hybridization reaction mixture affects the kinetics of DNA-RNA or DNA-cDNA reassociation, and theoretical formulae were derived as a function of these ratios. From these formulae, it was found that the DNA/RNA of the DNA/cDNA ratio did not much affect the initial reaction rates of hybridization, but greatly affected the terminal value for the extent of hybrid formation. Therefore the results obtained when one normalizes the experimental data for hydridization and derives the reiteration frequency from a number called the ‘half Cot’ (Cot 1/2) are not accurate, especially in the presence of a moderate excess of DNA. A simple method for the estimation of gene reiteration was demonstrated that did not use the half Cot value in the determination. This simple method is useful even if DNA-RNA or DNA/cDNA hybridization are done with a moderate excess of DNA. With mouse myeloma cells as a model system, the gene reiteration of the 28S rRNA cristron was determined.

THE SILVER CATALYZED OXIDATION OF ETHYLENE: II. KINETICS OF C2H4 OXIDATION

1954 ◽  
Vol 32 (4) ◽  
pp. 415-431 ◽  
Author(s):  
A. Orzechowski ◽  
K. E. MacCormack
Keyword(s):  
Total Pressure ◽  
Present Series ◽  
Initial Reaction ◽  
Flow Rates ◽  
Flow Type ◽  
Partial Pressures ◽  
C2h4 Oxidation ◽  
Kinetics Of ◽  
Catalyzed Oxidation ◽  
Type Apparatus

A flow-type apparatus is described and results given for the investigation of the kinetics of the silver catalyzed oxidation of C2H4 by oxygen. Using N2 as diluent, the concentrations of both O2 and C2H4 were varied independently from 9.9 to 79.0% and 2.35 to 9.40% respectively, whilst maintaining a total pressure of 1 atmosphere. Flow rates were varied to give a range of contact times varying from 0.05 to 1 sec. Measurements were made at 234 °C and 274 °C and the data used to estimate initial reaction velocities for both EtO and CO2 formation as a function of O2 and C2H4 partial pressures. These rates were fitted successfully to equations deduced theoretically in Part IV of the present series.

scholarly journals Hydrolysis of sunflower seed meal lignocellulosic fraction by free and immobilized cellulases

2020 ◽  
Vol 11 (15) ◽  
Author(s):  
Marija Ćorović
Keyword(s):  
Sunflower Seed ◽  
Catalytic Efficiency ◽  
Cost Effective ◽  
Reaction Rates ◽  
Seed Meal ◽  
Initial Reaction ◽  
Amino Groups ◽  
Spacer Arm ◽  
Optimized Conditions ◽  
Hydrolysis Of

Lignocellulosic biomass is widely abundant in nature and recognized aspotential renewable energy source. Its efficient transformation into bio-basedfuels is enabled only after adequate pretreatment, followed by enzymaticsacharification and microbial fermentation. Hereby we present application of twocellulase preparations – from Aspergillus niger and Trichoderma reesei (Celluclast®)in treating sunflower seed meal lignocellulosic fraction (SSMLF). Temperature andpH optimums of two enzymes were determined – 52 °C and pH4.8 for A. nigercellulase and 55 °C and pH4.5 for Celluclast®. At optimized conditions, milledSSMLF was hydrolyzed by both biocatalysts. With A. niger cellulase higher initialreaction rates were accomplished and yield of 70 mM glucose equivalent wasobtained with 6 % (w/v) of enzyme after 6 hours. On the other hand, applicationof Celluclast® led to lower initial reaction rates and yielded 25 mM of glucoseequivalent with 10 % (v/v) of enzyme. To ensure cost-effective application ofA. niger cellulase, the possibility of its immobilization on different supports wasinvestigated. By using porous methacrylate-based carrier with C6 spacer arm andprimary amino groups – LifetechTM ECR8409, preparation with highest activity wasproduced. This preparation was successfully applied in saccharification of SSMLFand showed unchanged catalytic efficiency comparing to free enzyme.

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