Rate Enhancement of Nickel(II)-pada Complex-Formation in Mixed Sodium Perfluorooctanoate/Octanesulfonate Micellar Solutions

1990 ◽  
Vol 43 (1) ◽  
pp. 11 ◽  
Author(s):  
VC Reinsborough ◽  
TDM Stulz ◽  
XY Xiang
Keyword(s):  
Binding Constants ◽  
Kinetic Studies ◽  
Bidentate Ligand ◽  
Bulk Solution ◽  
Complexation Reaction ◽  
Reaction Volume ◽  
Rate Enhancement ◽  
Maximum Value ◽  
Sodium Perfluorooctanoate ◽  
Robinson Equation

Kinetic studies of the Niaq2+ ion complexation with the bidentate ligand pyridine-2-azo-p-dimethylaniline ( pada ) were conducted by the stopped-flow technique in the presence of mixed micelles of sodium perfluorooctanoate ( spfo ) and sodium octanesulfonate ( sos ). Binding constants for Niaq2+ and pada partitioning between bulk solution and micelles were determined through solubility measurements and the murexide techniques respectively. The molar reaction volume for the surfactant was obtained through the fitting of the kinetic data and partitioning constants to the Robinson equation. It was found that spfo micelles promoted the complexation reaction 400-fold just beyond the critical micelle concentration but this maximum value decreased with sos , NaCl or further spfo addition. The unexpected effectiveness of spfo in rate enhancement is due to its compact micellar reaction volume of 0.16 dm3 mol-1. The kinetic results are consistent with spfo and sos forming separate micelles of pure or almost pure composition.

Micellar rate enhancement studies in mixed sodium fluorocarbon/hydrocarbon surfactant solutions

1992 ◽  
Vol 70 (6) ◽  
pp. 1581-1585 ◽  
Author(s):  
Terrence J. Connolly ◽  
Vincent C. Reinsborough
Keyword(s):  
Mixed Micelles ◽  
Anionic Surfactants ◽  
Binding Constants ◽  
Kinetic Studies ◽  
Bulk Solution ◽  
Reaction Volume ◽  
Sodium Decylsulfate ◽  
The Difference ◽  
Anionic Micelles ◽  
Robinson Equation

Stopped-flow kinetic studies were conducted in mixed micellar solutions of fluorocarbon and hydrocarbon anionic surfactants to determine the prevalent micellar form. The probe reaction was the Niaq2+/pyridine-2-azo-p-dimethylaniline (PADA) complexation, which is many times accelerated in the presence of anionic micelles. Binding constants for Niaq2+ and PADA partitioning between bulk solution and micelles were determined through the murexide technique and solubility measurements respectively and the molar reaction volume was obtained from the Robinson equation. The three binary surfactant systems investigated had sodium perfluoroheptanoate as the fluorocarbon surfactant while the hydrocarbon surfactants were sodium decylsulfate, sodium nonanesulfonate, and sodium octanesulfonate. The kinetic results were consistent with unimicellar composition in all three systems which was not the behaviour previously found with the sodium octane sulfonate/sodium perfluoroctanoate system. The difference was attributed to closer similarity in the surfactant pair hydrophobicities as revealed through their critical micelle concentrations. Another finding was that mixed micelles synergistically can lead to a much greater solubilization of PADA than is possible through either of the pure surfactants.

Rate enhancement of the nickel(II)-pada complex formation in sodium alkanesulfonate micellar solutions

1982 ◽  
Vol 35 (1) ◽  
pp. 15 ◽  
Author(s):  
JR Hicks ◽  
VC Reinsborough
Keyword(s):  
Complex Formation ◽  
Chain Length ◽  
Micellar Solution ◽  
Binding Constants ◽  
Bidentate Ligand ◽  
Kinetic Constants ◽  
Micellar Solutions ◽  
Reaction Volume ◽  
Rate Of Reaction ◽  
Alkyl Sulfates

Sodium alkanesulfonates (C9, C8, C7, and C6) in micellar solution have been used to enhance the rate of reaction between Niaq2+ and the bidentate ligand pyridine-2-azo-p-dimethylaniline (pada) at 298.2 K. A Berezin-like model has been used to account for the observed kinetic constants in terms of the binding constants of each of the reagents to the micelles and the reaction volume and the concentration of the micellar surfactant. For a given chain length, the alkanesulfonates are about 25 % less effective than alkyl sulfates in promoting the rate of reaction and the model accounts for this successfully.

scholarly journals Binding of cadmium to soil humic acid as a function of carboxyl group content

2010 ◽  
Vol 29 (2) ◽  
pp. 215 ◽  
Author(s):  
Tatjana Anđelković ◽  
Ružica Nikolić ◽  
Aleksandar Bojić ◽  
Darko Anđelković ◽  
Goran Nikolić
Keyword(s):  
Humic Acid ◽  
Binding Constants ◽  
Formation Constants ◽  
Carboxyl Groups ◽  
Complexation Reaction ◽  
Infrared Spectroscopic Analysis ◽  
Soil Humic Acid ◽  
Carboxyl Group Content ◽  
The Stability ◽  
Scatchard Plots

The binding of Cd(II) to soil humic acid (HA) at pH 6.5 and in 0.1 mol/L KNO3 ionic medium, was studied by potentiometric titration with a cadmium ion selective electrode. The influence of carboxyl groups in cation-humic interactions was investigated by selective blocking of humic acid carboxyl groups with thionyl chloride and methanol. Infrared spectroscopic analysis confirmed that esterification took place. Differences between underivatized and derivatized HA complexation properties are ascribed to carboxyl groups. The Scatchard plots and incremental formation constants were used to obtain values for Cd-binding constants, for both HAs. The derivatization decreased the number of HA complexing sites by approximately 60 %, which correlates with acid-base properties of both HAs, studied by barium hydroxide and calcium acetate exchange methods. The stability constants for binding at the strongest sites (logKINT) was larger for underivatized HA (5.40) than for derivatized HA (4.92), indicating greater stability in the case when carboxyl groups are involved in complexation reaction.

Hydrolysis of aryl hydrogen maleate esters mediated by cyclodextrins — Effect on the intramolecular catalysis

2005 ◽  
Vol 83 (9) ◽  
pp. 1281-1286 ◽  
Author(s):  
Gabriel O Andrés ◽  
O Fernando Silva ◽  
Rita H de Rossi
Keyword(s):  
Maleic Anhydride ◽  
Transition State ◽  
Rate Constant ◽  
Association Constant ◽  
Kinetic Studies ◽  
Association Constants ◽  
Bulk Solution ◽  
Intramolecular Catalysis ◽  
Hydrolysis Of ◽  
Nonlinear Fashion

Kinetic studies of the hydrolysis of Z-aryl hydrogen maleates (Z = H, p-CH3, m-CH3, p-Cl, m-Cl) were carried out in the presence and absence of hydroxypropyl-β-cyclodextrin (HPCD) at variable pH from 1.00 to 3.00. The reaction involves the formation of maleic anhydride as an intermediate and the rate of its formation is strongly dependent on the pH. This is because the neighboring carboxylate group is a better catalyst than the carboxylic group. The rate constant for the formation of maleic anhydride decreases as the HPCD concentration increases in a nonlinear fashion. The results were interpreted in terms of the formation of a 1:1 inclusion complex of the esters with HPCD. The neutral (HA) and anionic (A) species of the substrate have different association constants (K[Formula: see text] and K[Formula: see text]). In all cases studied, K[Formula: see text] is higher than K[Formula: see text] for the same substrate. This difference is responsible for a decrease in the amount of the anionic substrate (reactive species) in the presence of HPCD, which results in a diminution of the observed rate constant. Besides, the rate constant for the reaction of the complexed substrate is smaller than that in the bulk solution indicating that the transition state of the cyclodextrin mediated reaction is less stabilized than the anionic substrate. The values of ΔΔG‡ are almost independent of the substituent on the aryl ring and range within 0.48 and 1.05 kcal mol–1 (1 cal = 4.184 J). There is no correlation between KTS and the association constant of the substrate indicating that the factors stabilizing the transition state are different from those that stabilize the substrate. Key words: cyclodextrins, intramolecular catalysis, hydrolysis, inhibition.

UV-vis and Binding Studies of Cobalt Tetrasulfophthalocyanine–Thiolate Complexes as Intermediates of the Merox Process

1999 ◽  
Vol 03 (07) ◽  
pp. 654-666 ◽  
Author(s):  
ALI NAVID ◽  
EDUARD M. TYAPOCHKIN ◽  
CHARLES J. ARCHER ◽  
EVGUENII I. KOZLIAK
Keyword(s):  
Charge Transfer ◽  
Charge Transfer Band ◽  
Broad Band ◽  
Spectral Feature ◽  
Binding Constants ◽  
Kinetic Studies ◽  
Binding Studies ◽  
Π Stacking ◽  
Vis Spectroscopy ◽  
Major Factors

Intermediates of the cobalt tetrasulfophthalocyanine ( CoTSPc )-catalyzed thiol autoxidation were studied by UV-vis spectroscopy. All thiolates react with CoTSPc resulting in the formation of 1:1 complexes. Three major factors control both the stability and aggregation of the complexes: thiolate basicity, metal-to-ligand charge transfer (MLCT) and π stacking. Basic thiolates partially reduce C oII TSPc , whereas CoTSPc complexes with low-basicity aliphatic thiolates ( p K a < 4) do not exhibit Co (II) reduction, based on the absence of the characteristic Co (I) charge transfer band at 450 nm. CoTSPc complexes with aliphatic and bulky aromatic thiolates appear to be aggregated in aqueous solutions and are characterized by a broad band at 650 nm. Non-bulky aromatic thiolates of low basicity ( p K a < 6) form unique stable monomeric Co II TSPc complexes. This unique spectral feature can be attributed to π stacking between the phthalocyanine ring and thiolate. Comparison of binding constants shows that the partial reduction of Co (II) significantly contributes to the thiolate binding. A combination of aromatic π stacking and MLCT appears to be responsible for the observed 1000-fold stronger binding of non-basic aromatic thiolates as compared with aliphatic ligands of similar basicity. Kinetic studies confirm the importance of the thiolate binding type for catalysis.

Kinetic Studies of CdS Formation for a Better Understanding of Chemical Buffer Layer Deposition

2009 ◽  
Vol 1165 ◽  
Author(s):  
Krzysztof Wilchelmi ◽  
Diana Förster ◽  
Axel Neisser ◽  
Reinhard Schomäcker
Keyword(s):  
Buffer Layer ◽  
Kinetic Studies ◽  
Reynold Number ◽  
Window Layer ◽  
Bulk Solution ◽  
Phase Reaction ◽  
Solution Deposition ◽  
Layer Deposition ◽  
Kinetics Of

AbstractCdS is an important part of CIGS-based photovoltaics as a buffer layer between the absorber and the window layer. Chemical Bath Deposition (CBD) is the most common way of depositing CdS. Due to the nature of the CBD process CdS forms not only on the absorber layer surface but also in the bulk solution. In order to control the deposition of CdS at the surface and to avoidCdS formation in the bulk solution the kinetics of these reactions must be understood. In this work we study the formation of CdS in the chemical bath by using in situ spectroscopic extinction measurements. By monitoring the absorbance of the solution we are able to observe the bulk phase reaction (chemical formation of CdS in solution). Deposition of CdS (growth of the CdS layer at the surface) is investigated by measuring the CdS layer thickness after the reaction. The kinetics of both reactions were investigated by a systematic variation of temperature, initial reactant concentration, Reynold number as well as time. Finally the results of our study suggest a model of growth behaviour based on molecule-by-molecule deposition, which explains especially the dependency on temperature and hydrodynamics.

Stopped-Flow Kinetic Studies of the Interaction of Bovine Folate Binding Protein (FBP) and Folate

2006 ◽  
Vol 26 (4) ◽  
pp. 291-299 ◽  
Author(s):  
Ulla Christensen ◽  
Jan Holm ◽  
Steen Ingemann Hansen
Keyword(s):  
Binding Protein ◽  
Binding Constants ◽  
Kinetic Studies ◽  
Human Albumin ◽  
Time Range ◽  
Stopped Flow ◽  
Protein Fluorescence ◽  
Folate Binding Protein ◽  
Binding Model ◽  
One Step

The kinetics of the interaction of bovine folate binding protein and folate at pH 7.4 and 5.0 were followed by measuring the changes of the intrinsic protein fluorescence intensity using the stopped-flow technique, which enables the study of reactions from the millisecond time-range. Our results immediately reject a simple one-step binding model, which requires a linear dependence of the observed rate constant on the concentration of the ligand. Thus, we are able to conclude that at pH 5.0 the interaction occurs in two steps and at pH 7.4 in three steps. Changes of fluorescence spectra at equilibrium were used to estimate the overall binding constants. Comparative studies on the binding of folate to human albumin are also reported.

Micellar catalysis in mixed anionic/cationic surfactant systems

1994 ◽  
Vol 72 (12) ◽  
pp. 2443-2446 ◽  
Author(s):  
Yvette L. Favaro ◽  
Vincent C. Reinsborough
Keyword(s):  
Cationic Surfactant ◽  
Sodium Dodecylsulfate ◽  
Kinetic Studies ◽  
Micellar Catalysis ◽  
Stopped Flow ◽  
Complexation Reaction ◽  
Dodecyltrimethylammonium Bromide ◽  
Micellar Solutions ◽  
Decyltrimethylammonium Bromide ◽  
Anionic Micelles

Dye solubility and stopped-flow kinetic studies were conducted in sodium dodecylsulfate/dodecyltrimethylammonium bromide and sodium dodecylsulfate/decyltrimethylammonium bromide micellar solutions with excess anionic surfactant. The enhanced rate in the presence of anionic micelles of the Ni2+(aq)/pyridine-2-azo-p-dimethylaniline (PADA) complexation reaction was used as a probe of the mixed micellar situation. PADA solubilities and the kinetic parameters derived through the Robinson model for micellar catalysis were consistent with a complete incorporation of the cationic surfactant into the sodium dodecylsulfate micelles.

Effect of short-chained sodium alkylsulfate micelles on the kinetics of metal complex formation

1981 ◽  
Vol 59 (9) ◽  
pp. 1361-1367 ◽  
Author(s):  
Paul D. I. Fletcher ◽  
Vincent C. Reinsborough
Keyword(s):  
Alkyl Chain ◽  
Binding Constants ◽  
Micelle Formation ◽  
Reaction Rates ◽  
Bidentate Ligand ◽  
Alkyl Chain Length ◽  
Stopped Flow ◽  
Micellar Solutions ◽  
Kinetics Of ◽  
Micelle Surface

The kinetics of the reaction between Niaq2+ and the bidentate ligand pyridine-2-azo-p-dimethylaniline (PADA) have been investigated in micellar solutions of sodium decyl-, octyl-, and hexylsulfates using the stopped-flow technique. The rate of enhancement decreased with decreasing alkyl-chain length and from the Berezin or Robinson model could be quantitatively related to the independently measured binding constants of Ni2+ ion and PADA to the micelle surface. The dramatic effect of micelles upon the reaction rates in different directions of the Ni2+/PADA and the Ni2+/murexide reactions served as sensitive indicators of the cmc even at the very limit of micelle formation which relatively concentrated sodium hexylsulfate solutions represent.

Sign in / Sign up

Export Citation Format

Share Document