The Kinetics of the Acid Hydrolysis of some Dipeptides in Acetic acid

1957 ◽  
Vol 10 (3) ◽  
pp. 268 ◽  
Author(s):  
RJL Martin
Keyword(s):  
Acetic Acid ◽  
Reaction Rate ◽  
Relative Rate ◽  
Water Concentration ◽  
Aqueous Acetic Acid ◽  
Aminoisobutyric Acid ◽  
Methyl Derivatives ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Bimolecular Mechanism

Glycylglycine and a number of its C-methyl derivatives have been hydrolysed with excess perchloric acid in aqueous acetic acid as solvent, and by varying the water content of the medium its effect on the reaction rate has been determined. It has been found that small changes in the water concentration cause reversals in the relative rate sequences in both series of dipeptides studied. In aqueous acetic acid containing more than 2 per cent. water the relative rate sequence in the first series is glycylglycine > alanylglycine > α-aminoisobutyrylglycine, but at water concentrations less than 2per cent. α-aminoisobutyrylglycine reacts faster than glycylglycine. It is concluded that increasing methylation has produced a change in mechanism whereby α-aminoisobutyrylglycine reacts by a unimolecular heterolysis rather than by the bimolecular mechanism given in the previous paper (Martin 1957). For the second series of dipeptides, the relative rate sequence is glycylglycine > glycylalanine > glycyl-α-aminoisobutyric acid for water concentrations greater than 2 per cent. At water concentrations less than 2 per cent. the rate sequence is reversed, so that glycyl-α-aminoisobutyric acid > glycylalanine > glycylglycine. This reversal is attributed to changes in the polar effect of the terminal carboxyl group which is brought about by increasing methylation.

scholarly journals Kinetics of Oxidation of Benzoin by N. Bromosuccinimide

2005 ◽  
Vol 4 (1) ◽  
pp. 55-61
Author(s):  
R. Sridharan ◽  
N. Mathiyalagan
Keyword(s):  
Dielectric Constant ◽  
Acetic Acid ◽  
Reaction Rate ◽  
Activation Parameters ◽  
Aqueous Acetic Acid ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
First Order Kinetics ◽  
Retarding Effect ◽  
Kinetics Of

Kinetics of Oxidation of Benzoin by N. Bromosuccinimide[NBS] 80% aqueous acetic acid has been investigated. The reaction follows first-order kinetics with respect to both[NBS] and [benzoin]. The effect of varying ionic strength and dielectric constant indicate the reaction is dipole-dipole type. Addition of succinimide(>NH), has a retarding effect on the rate of oxidation. The product of oxidation is benzil. By studying the effect of temparature on the reaction rate, the Arrhenius and the activation parameters have been calculated. A suitable mechanism has been proposed and a rate low explaining the experiment results is derived.

Acid hydrolysis of acetamide in aqueous acetic acid

1965 ◽  
Vol 18 (6) ◽  
pp. 807 ◽  
Author(s):  
RJL Martin
Keyword(s):  
Acetic Acid ◽  
Reaction Rate ◽  
Ion Pairs ◽  
Bimolecular Reaction ◽  
Aqueous Acetic Acid ◽  
Acid Base ◽  
Wide Range ◽  
Triple Ions ◽  
Association Equilibria ◽  
Hydrolysis Of

The hydrolysis of acetamide in acetic acid has been studied over a wide range of reactant and salt concentrations. The various acid-base and ionic association equilibria must be considered in the interpretation of the data. It is shown that the mechanism is a bimolecular reaction between water and the acetamidium ion and that the acetamidium ion pairs and triple ions have no reactivity. Polar substances such as water and acetamide, apart from undergoing reaction, also increase the reaction rate by favouring the dissociation of the ion pairs. Salts exhibit strong ionic strength and ion-pair effects.

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

scholarly journals Perborate Oxidation of Substituted 5-Oxoacids in Aqueous Acetic Acid Medium: A Kinetic and Mechanistic Study

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
S. Shree Devi ◽  
B. Muthukumaran ◽  
P. Krishnamoorthy
Keyword(s):  
Acetic Acid ◽  
Acid Medium ◽  
Reaction Rate ◽  
Reaction Medium ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Mechanistic Study ◽  
Aqueous Acetic Acid ◽  
Sodium Perborate ◽  
Acetic Acid Medium

Kinetics and mechanism of oxidation of substituted 5-oxoacids by sodium perborate in aqueous acetic acid medium have been studied. The reaction exhibits first order both in [perborate] and [5-oxoacid] and second order in [H+]. Variation in ionic strength has no effect on the reaction rate, while the reaction rates are enhanced on lowering the dielectric constant of the reaction medium. Electron releasing substituents in the aromatic ring accelerate the reaction rate and electron withdrawing substituents retard the reaction. The order of reactivity among the studied 5-oxoacids is p-methoxy ≫ p-methyl > p-phenyl > –H > p-chloro > p-bromo > m-nitro. The oxidation is faster than H2O2 oxidation. The formation of H2BO3+ is the reactive species of perborate in the acid medium. Activation parameters have been evaluated using Arrhenius and Eyring’s plots. A mechanism consistent with the observed kinetic data has been proposed and discussed. Based on the mechanism a suitable rate law is derived.

Spectroscopic analysis of proton exchange during the photocatalytic decomposition of aqueous acetic acid: an isotopic study on the product distribution and reaction rate

2018 ◽  
Vol 8 (22) ◽  
pp. 5886-5899 ◽  
Author(s):  
Saher Hamid ◽  
Ralf Dillert ◽  
Jenny Schneider ◽  
Detlef W. Bahnemann
Keyword(s):  
Carbon Dioxide ◽  
Acetic Acid ◽  
Molecular Hydrogen ◽  
Reaction Rate ◽  
Spectroscopic Analysis ◽  
Product Distribution ◽  
Proton Exchange ◽  
Photocatalytic Decomposition ◽  
Aqueous Acetic Acid ◽  
Isotopic Study

The photocatalytic decomposition of aqueous acetic acid into molecular hydrogen, carbon dioxide, and hydrocarbons employing platinized titania (Pt/TiO2) as a photocatalyst has been studied.

Kinetics and Mechanism of Oxidation of Dimethyl Sulphoxide by Mono- and Di-Substituted N,N-Dichlorobenzenesulphonamides in Aqueous Acetic Acid

2003 ◽  
Vol 58 (8) ◽  
pp. 787-794 ◽  
Author(s):  
B.Thimme Gowda ◽  
K. L. Jayalakshmi ◽  
K. Jyothi
Keyword(s):  
Acetic Acid ◽  
Benzene Ring ◽  
Dimethyl Sulphoxide ◽  
Aqueous Acetic Acid ◽  
Isokinetic Temperature ◽  
Free Energies ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of

In an effort to introduce N,N-dichloroarylsulphonamides of different oxidising strengths, four mono- and five di-substituted N,N-dichlorobenzenesulphonamides are prepared, characterised and employed as oxidants for studying the kinetics of oxidation of dimethyl sulphoxide (DMSO) in 50% aqueous acetic acid. The reactions show first order kinetics in [oxidant], fractional to first order in [DMSO] and nearly zero order in [H+]. Increase in ionic strength of the medium slightly increases the rates, while decrease in dielectric constant of the medium decreases the rates. The results along with those of the oxidation of DMSO by N,N-dichlorobenzenesulphonamide and N,N-dichloro-4- methylbenzenesulphonamide have been analysed. Effective oxidising species of the oxidants employed in the present oxidations is Cl+ in different forms, released from the oxidants. Therefore the introduction of different substituent groups into the benzene ring of the oxidant is expected to affect the ability of the reagent to release Cl+ and hence its capacity to oxidise the substrate. Significant changes in the kinetic and thermodynamic data are observed in the present investigations with change of substituent in the benzene ring. The electron releasing groups such as CH3 inhibit the ease with which Cl+ is released from the oxidant, while electron-withdrawing groups such as Cl enhance this ability. The Hammett equation, log kobs = −3.19 + 1.05 σ , is found to be valid for oxidations by all the p-substituted N,N-dichlorobenzenesulphonamides. The substituent effect on the energy of activation, Ea and log A for the oxidations is also analysed. The enthalpies and free energies of activation correlate with an isokinetic temperature of 320 K.

Kinetics of the hydrolysis of acyl chlorides in pure water

1967 ◽  
Vol 45 (14) ◽  
pp. 1619-1629 ◽  
Author(s):  
A. Queen
Keyword(s):  
Pure Water ◽  
Activation Parameters ◽  
Acyl Chlorides ◽  
Reversible Addition ◽  
Electron Donation ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Chlorine Bond ◽  
Oxygen Bond ◽  
Bimolecular Mechanism

The activation parameters ΔH≠, ΔS≠, and ΔCP≠ for the hydrolyses of a series of alkyl chloroformates and dimethylcarbamyl chloride in water have been determined. The results indicate that, with increasing electron donation to the chlorocarbonyl group, the mechanism changes from bimolecular to unimolecular (SN1) displacement at this position. For isopropyl chloroformate, some concurrent alkyl–oxygen bond fission is also indicated. The bimolecular mechanism involves reversible addition of water to the carbonyl group followed by ionization of the carbon–chlorine bond.

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