Kinetics of hydrogenation of alkynes and dienes on palladium catalyst

1987 ◽  
Vol 52 (12) ◽  
pp. 2909-2917 ◽  
Author(s):  
Libor Červený ◽  
Šárka Řehůřková
Keyword(s):  
Activated Carbon ◽  
Palladium Catalyst ◽  
Atmospheric Pressure ◽  
Reaction Rates ◽  
Initial Reaction ◽  
Hydrogenation Rate ◽  
Substrate Structure ◽  
The Individual ◽  
Kinetics Of ◽  
Relative Adsorption

Alkynic and dienic substrates (C6-C10) in hexane and methanol were hydrogenated over a catalyst of 3% Pd on activated carbon at 20 °C and atmospheric pressure. The initial reaction rates were measured for the individual substrates; the hydrogenation rates of the olefinic substances formed were also determined if the hydrogenation was selective. The selectivities in competitive hydrogenations of substrate pairs were established and the relative adsorption coefficients of the substrates were calculated from them. The effect of the substrate structure and the solvent effect on the hydrogenation rate and relative adsorptivity are discussed for the alkynic and dienic substances studied.

Kinetics of esterification of monoisopropylphenols with phosphoryl trichloride

1989 ◽  
Vol 54 (5) ◽  
pp. 1311-1317
Author(s):  
Miroslav Magura ◽  
Ján Vojtko ◽  
Ján Ilavský
Keyword(s):  
Liquid Phase ◽  
Rate Constants ◽  
Reaction Rates ◽  
Activation Energies ◽  
The Individual ◽  
Kinetics Of

The kinetics of liquid-phase isothermal esterification of POCl3 with 2-isopropylphenol and 4-isopropylphenol have been studied within the temperature intervals of 110 to 130 and 90 to 110 °C, respectively. The rate constants and activation energies of the individual steps of this three-step reaction have been calculated from the values measured. The reaction rates of the two isomers markedly differ: at 110 °C 4-isopropylphenol reacts faster by the factors of about 7 and 20 for k1 and k3, respectively. This finding can be utilized in preparation of mixed triaryl phosphates, since the alkylation mixture after reaction of phenol with propene contains an excess of 2-isopropylphenol over 4-isopropylphenol.

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.

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.

Determination of structure parameters of platinum hydrogenation catalysts and their supports

1987 ◽  
Vol 52 (11) ◽  
pp. 2680-2686
Author(s):  
Jiří Růžička ◽  
Jiří Hanika ◽  
Zdeněk Sedláček ◽  
Vlastimil Růžička
Keyword(s):  
Experimental Data ◽  
Activated Carbon ◽  
Specific Surface ◽  
Reaction Rates ◽  
Initial Reaction ◽  
Structure Parameters ◽  
Hydrogenation Catalysts ◽  
Subsequent Calcination ◽  
Pore Radii Distribution

Six catalysts containing 5 and 6.1 wt. % Pt were prepared by impregnation of activated carbon (Atlas AET 300) with H2PtCl6 from aqueous solutions and subsequent calcination and reduction with hydrogen at 100, 200, and 300 °C. The specific surface area was determined for the catalysts, saturated supports and the untreated support. The adsorption isotherms of n-pentane at 0 °C were measured for the support, saturated support and catalyst (100 °C), and the experimental data were correlated by the BET, Langmuir, and Dubinin equations; the pore radii distribution was also calculated for them. The activities of the catalysts were evaluated by measuring the initial reaction rates of hydrogenation of 1-octene and nitrobenzene.

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 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.

Kinetics of 1-butanol, di-(1-butyl) ether and 1-butene reactions on aluminas partially deactivated by sodium

1989 ◽  
Vol 54 (11) ◽  
pp. 2985-2997 ◽  
Author(s):  
František Krampera ◽  
Ludvík Beránek
Keyword(s):  
Vapour Phase ◽  
Reaction Rates ◽  
Product Formation ◽  
Sodium Content ◽  
Butyl Ether ◽  
Deactivation Kinetics ◽  
Two Factors ◽  
Best Fitting ◽  
The Individual ◽  
Kinetics Of

The initial rates of six reactions taking place in 1-butanol dehydration at 260 °C in vapour phase were measured on aluminia samples differing in sodium content. The reactants were 1-butanol, di-(1-butyl) ether and 1-butene, resp. The parameters of the best fitting rate equation for each reaction were evaluated. The reaction rates as well as the rate constants and adsorption coefficients of the individual reactions show different sensitivity to datalyst acidity. Therefore, the selectivity of product formation can be influenced by sodium content of the catalyst. The selectivities (with the exception of 1-butene izomerization) strongly depend also on the partial pressure of the starting reactants. Thus, these two factors can be used to control the selectivity for preparative purposes. The results of this paper clearly demonstrate the nonseparability of the deactivation kinetics in 1-butanol dehydration on sodium poisoned aluminas.

Kinetics of Triplet Sublevel Selective Photochemical Reactions in the Solid State

1981 ◽  
Vol 36 (7) ◽  
pp. 743-750
Author(s):  
Manfred Gehrtz ◽  
Christoph Bräuchle ◽  
Jürgen Voitländer
Keyword(s):  
Solid State ◽  
Reaction Rates ◽  
Photochemical Reactions ◽  
Solid State Reactions ◽  
Physical Activation ◽  
Zero Field ◽  
Excited Triplet ◽  
The Individual ◽  
Activation Rates ◽  
Kinetics Of

Abstract A detailed description of the overall kinetics of photochemical reactions has to deal with photo-physical activation and de-activation rates as well as with true photochemical rates. Based on the hypothesis that for photoreactions involving the lowest excited triplet state the chemical reaction rates of the individual triplet zero-field levels have different values, a method is presented for the evaluation of these rates from bulk measurements under steady state illumination conditions. The complications arising from the detection of solid state reactions are discussed, and a simple solution is given, illustrated by a numerical example.

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.

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.

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