Influence des composés organiques sur la vitesse d'apparition du complexe de transfert de charge 1Sn(II)—4Sn(IV) dans les bains acides d'étamage brillant

1978 ◽  
Vol 56 (20) ◽  
pp. 2624-2629 ◽  
Author(s):  
Gaston Verville
Keyword(s):  
Charge Transfer ◽  
Organic Compounds ◽  
Charge Transfer Complex ◽  
Sulphate Solution ◽  
Initial Concentration ◽  
Rate Of Hydrolysis ◽  
The Stability ◽  
Hydrolysis Of

The effect of a number of organic compounds on the rate of formation of 1Sn(II)–4Sn(IV) charge transfer complex in acidic stannous sulphate solutions and on the stability of these solutions has been determined by measuring, spectrophotometrically, the change of absorption of these solutions with time. From the results, it is possible to classify these organic compounds into three broad categories in terms of how they affect the formation of the charge transfer complex and the stability of the solution.These results have been interpreted taking into account that the formation of the 1Sn(II)–4Sn(IV) complex depends on the initial concentration of stannic ions present as an impurity in the stannous sulphate solution, the rate of oxidation of the stannous ions, the rate of hydrolysis of the stannic ions, and the stability of stannic colloids that are formed.

SUBSTITUTION AT OCTAHEDRAL CENTERS: II. EFFECT OF SALTS UPON THE RATE OF HYDROLYSIS OF THE HALOPENTAMMINECHROMIUM(III) IONS

1961 ◽  
Vol 39 (11) ◽  
pp. 2371-2379 ◽  
Author(s):  
T. P. Jones ◽  
W. E. Harris ◽  
W. J. Wallace
Keyword(s):  
Charge Transfer ◽  
Transfer Effect ◽  
Ion Pair ◽  
Pair Formation ◽  
Sodium Salts ◽  
Rate Acceleration ◽  
Rate Of Hydrolysis ◽  
A Charge ◽  
Hydrolysis Of ◽  
Octahedral Configuration

A study of the hydrolysis of the halopentamminechromium(III) ions in the presence of the sodium salts of weak acids reveals a rate acceleration due to specific ion-pair formation. The acceleration is due partly to a charge-transfer effect and partly to the fact that the ion helps to maintain the octahedral configuration of the complex in the transition state. It is concluded that the reaction occurs by dissociation, but without collapse of the structure to a five-co-ordinated intermediate.

Study and modeling of mechanisms of cholinesterasis reactions in order to improve their catalytic properties in the neutralization reactions of organophosphorous compounds

2020 ◽  
pp. 134-174
Author(s):  
Sergey Varfolomeev ◽  
Bella Grigorenko ◽  
Sofya Lushchekina ◽  
Patrick Masson ◽  
Galina Mahaeva ◽  
...  
Keyword(s):  
First Generation ◽  
Organophosphorus Compounds ◽  
Protein Molecule ◽  
Catalytic Antibodies ◽  
High Rate ◽  
Biological Targets ◽  
Organophosphorous Compounds ◽  
Rate Of Hydrolysis ◽  
The Stability ◽  
Hydrolysis Of

“Biocleaners” or “bioscavengers” are biological objects (enzymes, catalytic antibodies) that are capable of binding and/or hydrolyzing organophosphorus compounds (OPC). Their use seems to be the most effective alternative to traditional antidotes to neutralize or detoxify OPC. The introduction of bioscavengers allows neutralizing toxicant molecules in the bloodstream before they reach their biological targets, thereby providing protection against poisoning. Bioscavengers of the first-generation neutralized OPC molecules by stoichiometrically binding to them. The safety and efficacy of human butyrylcholinesterase (BChE) for protecting against OPC poisoning has been shown. However, the stoichiometric neutralization of OPC requires the introduction of a huge amount of expensive biopharmaceuticals. Catalytic bioscavengers that hydrolytically neutralize OPC were introduced at a much lower dose to achieve the same degree of effectiveness. The most effective catalytic bioscavengers are enzymes. The most promising enzymes are artificial mammalian paraoxonase mutants and bacterial phosphotriesterases. However, studies of other enzymes, such as prolidases, oxidases, artificial mutants of cholinesterases and carboxyl esterases and catalytic antibodies are actively ongoing. Since OPC are pseudosubstrates of cholinesterases (ChEs), a detailed description of the mechanisms of inhibition, dealkylation, and spontaneous reactivation of phosphorylated ChEs is critical for the development of ChEs mutants with a high rate of hydrolysis of OPC. The review presents an analysis of different views on the mechanisms of interaction of ChEs with OPC, discusses the possible directions of creating effective catalytic biological traps based on BChE and changes in their mechanism of action as compared to the native enzyme. A separate section is devoted to the effect of mutations, both polymorphic and artificial, on the stability of the protein molecule of BChE.

scholarly journals Stability of unimolecular films of 32P-labelled lecithin

1967 ◽  
Vol 105 (1) ◽  
pp. 401-407 ◽  
Author(s):  
H. Hauser ◽  
R. M. C. Dawson
Keyword(s):  
Pressure Change ◽  
Ion Concentration ◽  
Hydrolysis Rate ◽  
Ion Distribution ◽  
Rapid Perfusion ◽  
Poisson Boltzmann ◽  
Rate Of Hydrolysis ◽  
Poisson Boltzmann Equation ◽  
The Stability ◽  
Hydrolysis Of

1. The stability of monolayers of a highly unsaturated yeast lecithin labelled with 32P has been investigated by a surface radioactivity technique. 2. Lecithin films on distilled water at all surface pressures between 6 and 48dynes/cm. were completely stable on rapid perfusion of the subphase and on addition of ionic amphipathic substances to the film. 3. Ultrasonically treated lecithin added to the subphase caused a slow loss of surface radioactivity but little pressure change. 4. The addition of proteins to the subphase caused negligible changes in the film even when conditions were favourable for electrostatic heterocoagulation and penetration. 5. Lecithin films were not hydrolysed by a strongly acid subphase at room temperature. The very low rate of hydrolysis produced by alkali was proportional to the subphase OH−ion concentration: the apparent activation energy and temperature coefficient (Q10) of the reaction were 14250 cal. and 2·37 respectively. 6. Alkaline hydrolysis of lecithin monolayers was markedly stimulated by adding methanol (10–20%, v/v) to the subphase. The addition of ionic amphipaths to the monolayer had the expected type of effect on the hydrolysis rate, but its magnitude was far less than that suggested by an application of the Poisson–Boltzmann equation for ion distribution at a charged interface (Davies & Rideal, 1963).

THE HYDROLYSIS OF ACETIC ANHYDRIDE IN WATER AND IN THE SYSTEM WATER: METHYL ETHYL KETONE

1950 ◽  
Vol 28b (11) ◽  
pp. 663-670
Author(s):  
E. N. Banks ◽  
A. E. Marshall ◽  
R. W. Vollett ◽  
R. R. McLaughlin
Keyword(s):  
Acetic Anhydride ◽  
Methyl Ethyl Ketone ◽  
Catalytic Effect ◽  
Methyl Ethyl ◽  
Initial Concentration ◽  
Velocity Constant ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Order Rate Equation ◽  
System Water

The rate of hydrolysis of acetic anhydride at 25 °C. in water (I), in solutions of methyl ethyl ketone (MEK) in water (II), and in solutions of water in MEK (III) have been studied. In I the observation of previous investigators that the velocity constant varies linearly with the initial concentration of acetic anhydride, but for any given initial concentration of acetic anhydride the reaction is pseudomonomolecular, was confirmed and extended. In II the velocity constant is lower than in I and decreases linearly with increasing concentration of MEK, but, again, the reaction is pseudomonomolecular for any given initial concentration of acetic anhydride. An equation and a nomogram that relate the velocity constant to the initial concentration of acetic anhydride, MEK, and water are presented. In III the second-order rate equation must be modified to compensate for the presumed catalytic effect of the hydrogen ion produced by hydrolysis.

scholarly journals Presence or absence of a novel charge-transfer complex in the base-catalyzed hydrolysis of N-ethylbenzamide or ethyl benzoate

2013 ◽  
Vol 9 ◽  
pp. 185-196 ◽  
Author(s):  
Shinichi Yamabe ◽  
Wei Guan ◽  
Shigeyoshi Sakaki
Keyword(s):  
Charge Transfer ◽  
Charge Transfer Complex ◽  
Ethyl Benzoate ◽  
Mulliken Charge ◽  
Water Molecules ◽  
Elementary Processes ◽  
General Base ◽  
Rate Determining Step ◽  
Proton Transfers ◽  
Hydrolysis Of

Reaction paths of base-catalyzed hydrolyses of isoelectronic substrates, Ph–C(=O)–X–Et [X = O (ethyl benzoate) and X = NH (N-ethylbenzamide)], were traced by DFT calculations. To simulate bond interchanges accompanied by proton transfers, a cluster model of Ph–C(=O)–X–Et + OH−(H2O)16 was employed. For X = O, three elementary processes and for X = NH four ones were obtained. The rate-determining step of X = O is the first TS (TS1, the OH− addition step), while that of X = NH is TS2. TS2 of X = NH leads to a novel Mulliken charge-transfer complex, Ph–(OH)(O=)C∙∙∙N(H2)–Et. The superiority or inferiority between the direct nucleophilic process or the general base-catalyzed process for TS1 was examined with the model Ph–C(=O)–X–Et + OH−(H2O) n , n = 3, 5, 8, 12, 16, 24 and 32. The latter process was calculated to be more favorable regardless of the number (n, except n = 3) of water molecules. The counter ion Na+ works unfavorably on the ester hydrolysis, particularly on TS1. A minimal model of TS1 was proposed and was found to be insensitive to n.

scholarly journals Antitumour Metallocenes: Effect of DMSO on the Stability of Cp2TiX2 and Implications for Anticancer Activity

1998 ◽  
Vol 5 (4) ◽  
pp. 207-215 ◽  
Author(s):  
George Mokdsi ◽  
Margaret M. Harding
Keyword(s):  
Nmr Spectroscopy ◽  
Aqueous Solutions ◽  
Anticancer Activity ◽  
Active Species ◽  
Aromatic Rings ◽  
Cyclopentadienyl Ligands ◽  
Rate Of Hydrolysis ◽  
The Stability ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of

The rate of hydrolysis of the aromatic rings of Cp2TiX2 [X = CI 1, O2CCCl3  8 and O2CCH2NH3Cl  13], in aqueous solutions, 10%DMSO and 100% DMSO have been studied by H1NMR spectroscopy. Rapid hydrolysis of both the carboxylate and cyclopentadienyl ligands in Cp2TiX2[X = O2CCCl3,O2CCH2NH3Cl] occurs in DMSO to give biologically inactive species. The rate of these reactions are concentration dependent as dilution of these samples with saline or water to give the therapeutic conditions of 10%DMSO/90%H2O slows the hydrolysis chemistry. In contrast, samples of Cp2TiX2 [X = CI 1, O2CCH2NH3Cl  13], dissolved in water give solutions containing the presumed antitumour active species in which the halide or glycine ligands have been hydrolysed but the Cp rings remain metal bound.

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