Kinetic studies of the substitution reactions of the cis-dihalotetracarbonylmanganate(I) ions

1969 ◽  
Vol 47 (8) ◽  
pp. 1311-1319 ◽  
Author(s):  
Frank E. Smith ◽  
Ian S. Butler
Keyword(s):  
Halogen Bond ◽  
Kinetic Studies ◽  
Reaction Rates ◽  
Atomic Weight ◽  
Substitution Reactions ◽  
Dissociative Mechanism ◽  
First Order ◽  
Rate Determining Step ◽  
Rate Of Reaction ◽  
Substrate Independent

The substitution reactions of (C2H5)4[cis-Mn(CO)4X2], where X = Br or I, with a variety of ligands, L, were observed to take place with the loss of halide ion, X−, to form cis-Mn(CO)4LX and (C2H5)4NX. The reaction rates in s-tetrachloroethane were first order in substrate, independent of both the nature and the concentration of L, and decreased with increasing atomic weight of the halogen. A dissociative mechanism involving the breaking of a manganese–halogen bond as the rate-determining step is proposed. It is postulated that the order of reactivity of the substrates is most probably the result of an entropy rather than an enthalpy effect. The substitution reactions of (C2H5)4N[cis-Mn(CO)4BrI] in s-tetrachloroethane were also studied kinetically and found to be first order in substrate and independent of the nature and concentration of L. The products of these reactions, however, were mixtures of cis-Mn(CO)4LBr and cis-Mn(CO)4LI, and (C2H5)4NBr and (C2H5)4NI. A solvent study of the reaction between (C2H5)4N[cis-Mn(CO)4Br2] and P(C6H5)3 indicated that the rate of reaction tended to increase with increasing polarity of the solvent.

Reactions of metal carbonyl complexes. VIII. Kinetics and mechanisms of the substitution reactions of cis-Mn(CO)4LBr (L = PPh3, AsPh3, SbPh3) with group VA bidentate ligands

1976 ◽  
Vol 54 (18) ◽  
pp. 2833-2838 ◽  
Author(s):  
I. S. Butler ◽  
H. K. Spendjian
Keyword(s):  
Metal Carbonyl ◽  
Reaction Rates ◽  
Carbonyl Complexes ◽  
Bidentate Ligands ◽  
Substitution Reactions ◽  
Dissociative Mechanism ◽  
Parent Molecule ◽  
First Order ◽  
Metal Carbonyl Complexes ◽  
Rate Determining Step

The substitution reactions of cis-Mn(CO)4LBr (L = PPh3, AsPh3, SbPh3) with diphos, diarsine, and dipy (A—A) take place with the loss of one CO group and L to form fac-Mn(CO)3(A—A)Br. The observed reaction rates in CHCl3 solution are first order in substrate but depend on the nature of L and A—A, and in some cases the concentration of A—A as well. When L = PPh3 and A—A = diphos, and when L = AsPh3 and A—A = diphos, diarsine, or dipy, the rates are independent of [A—A]. For these reactions, an SN1 dissociative mechanism involving the rupture of one of the Mn—CO bonds as the rate-determining step is proposed. The observed positive entropies of activation (∼10 e.u.) for these reactions are supportive of the proposed mechanism. The reactions of cis-Mn(CO)4(SbPh3)Br with A—A are essentially independent of both the nature and the concentration of A—A. However, for these reactions, an SN1 dissociative mechanism involving the rupture of the Mn—SbPh3 bond as the rate-determining step is proposed; the observed positive ΔS≠ values (∼12 e.u.) are in accord with such a mechanism. The rates when L = PPh3 and A—A = diarsine or dipy are dependent on both the nature and the concentration of A—A. A mechanism involving rapid pre-equilibrium steps between the parent molecule and the intermediates, Mn(CO)3(PPh3)Br and Mn(CO)4Br, is proposed to account for the complex kinetic behaviour found for these reactions. These results are particularly noteworthy because octahedral first-row transition metal complexes generally undergo substitution reactions which are independent of the concentrations of the entering nucleophiles.

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.

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-.

scholarly journals Kinetics and Mechanism of Oxidation oft-Butylbenzylamine by Diperiodatoargentate(III) in Aqueous Alkali

2012 ◽  
Vol 9 (1) ◽  
pp. 203-210 ◽  
Author(s):  
Mahantesh A. Angadi ◽  
Suresh M. Tuwar
Keyword(s):  
Kinetic Studies ◽  
Active Species ◽  
Alkali Concentration ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Middle Range ◽  
Wide Range ◽  
Rate Of Reaction ◽  
Mechanism Of Oxidation ◽  
Kinetics Of

t-Butylbenzylamine (t-BA) is used as a free base in the synthesis of salbutamol drug. Its mechanism of oxidation was proposed from kinetic studies. The kinetics of oxidation oft-butylbenzylamine by diperiodatoargentate(III) (DPA) was studied spectrophotometrically by monitoring decrease in absorbance of DPA. The reaction was found to be first order each in [DPA] and [t-BA]. The effect of alkali concentration in a wide range on rate of reaction was studied. The rate of reaction was found to be increased with increase in [OH–] in the lower range of [OH–], decreasing effect in the middle range and at higher range again increasing effect on rate of reaction was observed. The added periodate retarded the rate of reaction. The polymerization test revealed that oxidation was occurred with the intervention free radical. A suitable mechanism was proposed for a middle range of [OH–]. The active species of silver(III) periodate for all the three different stages of [OH–] are assayed. Rate law was derived and verified. The oxidative product oft-BA was characterized by LC-ESI-MS spectra.

KINETIC STUDIES OF PROTON TRANSFER FROM PHENOLS TO TRINITROBENZYL ANION

1966 ◽  
Vol 44 (2) ◽  
pp. 119-124 ◽  
Author(s):  
J. A. Blake ◽  
M. J. B. Evans ◽  
K. E. Russell
Keyword(s):  
Proton Transfer ◽  
Rate Constants ◽  
Dissociation Constants ◽  
Kinetic Studies ◽  
Sodium Cation ◽  
Rate Determining Step ◽  
Rate Of Reaction ◽  
Hammett Relationship ◽  
Measurable Concentration ◽  
Acetic Acids

The rates of reaction of various phenols with the 2,4,6-trinitrobenzyl anion in the solvent ethanol have been determined by a spectrophotometric method. The rate constants at −40 °C are related to the dissociation constants of the phenols in water at 25 °C and the value of α in the Brönsted relation is 0.84 ± 0.07; α drops to 0.44 ± 0.05 if the results for the substituted acetic acids (1) are included. The rate constants for the phenols are also correlated by the Hammett relationship, the ρ value at −40 °C being 1.82 ± 0.2. The activation energies range from 9.4 to 10.9 kcal/mole.The rate of reaction of trinitrobenzyl anion with 3-methylphenol at −30 °C is reduced by a factor of 12 if the phenol is deuterated at the OH group and the solvent is deuteroethanol. The large isotope effect confirms that the rate-determining step involves proton transfer from the OH group of the phenol. Substitution of lithium or potassium cations for the sodium cation does not affect the rate constant at −10 °C.In the reaction with 3-methylphenol, a measurable concentration of trinitrobenzyl anion remains at equilibrium and the equilibrium constant for the reaction is 1.3 ± 0.2 at 25 °C. The heat and entropy changes are approximately −6.5 kcal/mole and −21 e.u./mole respectively.

scholarly journals Kinetic Study of the Herrmann–Beller Palladacycle-Catalyzed Suzuki–Miyaura Coupling of 4-Iodoacetophenone and Phenylboronic Acid

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 989
Author(s):  
Amine Bourouina ◽  
Alexis Oswald ◽  
Valentin Lido ◽  
Lu Dong ◽  
Franck Rataboul ◽  
...  
Keyword(s):  
Kinetic Study ◽  
Phenylboronic Acid ◽  
Sodium Methylate ◽  
Reaction Rates ◽  
Catalyst Stability ◽  
Initial Reaction ◽  
First Order ◽  
Average Value ◽  
Rate Determining Step ◽  
Global Rate

This article presents an experimental kinetic study of the Suzuki–Miyaura reaction of 4-iodoacetophenone with phenylboronic acid catalyzed by the Herrmann–Beller palladacycle. This catalyst, together with the solvent (ethanol) and the base (sodium methylate), were chosen to ensure catalyst stability and reactants solubility all along the reaction. Based on the study of initial reaction rates, a quasi-first-order was found for 4-iodoacetophenone with a first-order dependence on the initial concentration of palladium. A zero-order was found for the base and the phenylboronic acid. The oxidative addition step of the mechanism was thus considered as the rate determining step. A global rate law was derived and validated quantitatively. A global activation energy, with an average value of ca. 63 kJ/mol was determined.

Adsorption and Desorption Potential of Cadmium Using Green Algae: Equilibrium and Kinetic Studies

2015 ◽  
Vol 1130 ◽  
pp. 693-696 ◽  
Author(s):  
Z.S. Birungi ◽  
E.M.N. Chirwa
Keyword(s):  
Sorption Capacity ◽  
Regression Coefficient ◽  
Kinetic Studies ◽  
Adsorption And Desorption ◽  
First Order ◽  
Rate Of Reaction ◽  
Freshwater Bodies ◽  
Pseudo Second Order ◽  
Better Than ◽  
Stichococcus Bacillaris

Microalgae has a diversity of species found in freshwater bodies but only a few have been explored for their biosorption potential as compared to macro algae (sea weed). Equilibrium and kinetic experiments were used to estimate sorption capacity and rate of reaction respectively. Chloroidium saccharophilum had the highest sorption capacity (qmax) of 200 mg/g and lower affinity (b) of 0.0095 L/g for removal of Cd. However, Stichococcus bacillaris was the best adsorbent for Cd as it had both a higher qmaxand higher b of 125 and 0.049 L/g. The Langmuir and Pseudo-second order models performed better than the Freundlich and First-order models with a regression coefficient (R2) > 0.9. Adsorption and desorption efficiency was achieved highest for Stichococcus bacillaris at 95.8% and 73.49% respectively.

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.

scholarly journals HYDROLYSIS AND DEUTERATION OF GLYCYLGLYCINE CATALYZED BY DINUCLEAR [BMXDCu 2]4+ COMPLEX

2007 ◽  
Vol 15 (15) ◽  
pp. 15-27
Author(s):  
Ana Cristina Franzoi ◽  
Gledir T. Stein Martins ◽  
Sérgio Duvoisin Jr. ◽  
Bruno Szpoganicz
Keyword(s):  
Rate Constants ◽  
Kinetic Studies ◽  
Peptide Bond ◽  
Reaction Rates ◽  
Active Species ◽  
Individual Species ◽  
Specific Rate ◽  
First Order ◽  
Parallel Reactions ◽  
Semi Empirical

Kinetic studies of hydrolysis and deuteration of glycylglycine by dinuclear [BMXDCu 2]4+ complexes were following by NMR1H. Two parallel reactions were observed for the ternary system BMXD-Cu 2-Glycylglycine: peptide bond hydrolysis and NCH2 deuteration reactions. The reaction rates show the first-order behavior to the concentration of the ternary [BMXDCu2Glycylglycine] complex. The specific rate constants for the hydrolysis reaction are: KLCu2HGG4+ (L = BMXD and GG = glycylglycine) = 1,8 x 10-6 s-1; KLCu 2GG3+ = 2,3 x 10-6 s-1; KLCu2H-1GG2+, KLCu 2(OH)H-1GG+ and KLCu 2(OH) 2H-1GG = 0, and the specific deuteration rate constants for individual species are: KLCu 2HGG4+ = 3,9 x 10-6 s-1; KLCu 2GG3+ = 4,3 x 10-6 s-1; KLCu2H-1GG2+, KLCu2(OH)H-1GG+ and KLCu2(OH)2H-1GG = 0. The results show that the most active species toward hydrolysis and deuteration reactions are the protonated and non-protonated species, the former being the most reactive species. Semi-empirical calculations for energy minimization showed that the binuclear [BMXDCu 2]4+) complexes adopt the boat-type conformation, in order to accommodate the dipeptide glycylglycine.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. I. The substitution of thiocyanate into the cis-Chlorodimethylsulphoxidobisethylenediaminecobalt(III) ion in anhydrous dimethylsulphoxide and NN-dimethylformamide

1965 ◽  
Vol 18 (4) ◽  
pp. 453 ◽  
Author(s):  
LF Chin ◽  
WA Millen ◽  
DW Watts
Keyword(s):  
Activation Energy ◽  
Ion Pair ◽  
Second Order ◽  
Aprotic Solvents ◽  
Kcal Mole ◽  
Dissociative Mechanism ◽  
Thiocyanate Ion ◽  
First Order ◽  
Rate Determining Step ◽  
Dipolar Aprotic Solvents

The substitution of thiocyanate ion into the cis-chlorodimethylsulphoxidobisethylenediaminecobalt(III) ion, cis-(Coen2(DMSO)Cl)2+, has been studied in the solvents dimethylsulphoxide (DMSO) and NN-dimethylformamide (DMF). In DMSO the reaction shows second-order characteristics which are accounted for by an ion-pair dissociative mechanism (SNIIP). The activation energy is 30.1 kcal mole-1. In DMF the entry is first-order, the rate determining step being solvolysis to the intermediate cis-(Coen2(DMF)Cl)2+ which has been isolated as the nitrate. In high thiocyanate concentrations the rate shows some thiocyanate dependence due to the competition of ion-paired thiocyanate with the DMF solvent for coordination following the DMSO dissociation. The activation energy for this substitution is 17.5 kcal mole-1.

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