scholarly journals Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes

2007 ◽  
Vol 5 (3) ◽  
pp. 898-911 ◽  
Author(s):  
M. Ghoneim ◽  
E. Mabrouk ◽  
A. Hassanein ◽  
M. El-Attar ◽  
E. Hesham
Keyword(s):  
Schiff Bases ◽  
Reaction Pathway ◽  
Mercury Electrode ◽  
Transition Metal Ions ◽  
Electrode Reaction ◽  
Cyclic Voltammograms ◽  
Azomethine Group ◽  
Sulpha Drug ◽  
Controlled Potential ◽  
The Stability

AbstractThe electrochemical behavior of some sulpha drug-Schiff bases at a mercury electrode was examined in the Britton-Robinson universal buffer of various pH values (2.5–11.7) containing 20% v/v) of ethanol using DC-polarography, cyclic voltammetry and controlled-potential electrolysis. The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single, 2-electron, irreversible, diffusion-controlled cathodic step within the entire pH range which is attributed to the reduction of the azomethine group-CH=N- to -CH2-NH-. The symmetry transfer coefficient (α) of the electrode reaction and the diffusion coefficient (D 0) of the reactant species were determined. The electrode reaction pathway of the compounds at the mercury electrode was suggested to follow the sequence: H+, e−, e−, H+. The dissociation constant of the sulpha drug-Schiff bases, the stability constant and stoichiometry of their complexes with various divalent transition metal ions (Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) were determined potentiometrically at room temperature.

Synthesis and electroreduction of 2-[(8-hydroxyquinoline-5-yl)azo]benzo[c]cinnoline in DMSO–H2O (1:1) medium

2010 ◽  
Vol 75 (11) ◽  
pp. 1201-1216
Author(s):  
Funda Öztürk ◽  
Zehra Durmuş ◽  
Öznur Ölmez Uçkan ◽  
Emine Kiliç ◽  
Esma Kiliç
Keyword(s):  
Reaction Diffusion ◽  
Electrode Reaction ◽  
Basic Medium ◽  
Cyclic Voltammograms ◽  
H Nmr ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Constant Potential ◽  
Ph Range ◽  
Tlc Analysis

2-[(8-Hydroxyquinoline-5-yl)azo]benzo[c]cinnoline (HQAB) was prepared and characterized by elemental analysis, MS, FTIR and 1H NMR techniques. The electrochemical reduction of HQAB has been investigated by cyclic voltammetry, chronoamperometry and controlled potential electrolysis at mercury pool electrode in the pH range 3.5–9.4. The number of electrons transferred in the electrode reaction, diffusion coefficients and standart rate constants were calculated. In acidic medium, cyclic voltammograms display four cathodic peaks, with the total exchange of 6 e– and 6 H+. By contrast, the reverse scan displays two anodic peaks. Constant potential electrolysis at –1.0 V and TLC analysis of the product reveals that the reduction of azo group (in the bridge) in HQAB does not stop at the hydrazo stage but goes further through the cleavage of –NH–NH– linkage to give amino compounds as the final products. The voltammograms recorded in basic medium exhibit two cathodic peaks corresponding to 4 e–, 4 H+ and two reverse anodic peaks, and thus the reduction stopped at hydrazo stage. A tentative mechanism for the reduction has been suggested.

Electrochemical reduction of the nickel(II) dithiocarbamates at the mercury electrode

1976 ◽  
Vol 29 (6) ◽  
pp. 1191 ◽  
Author(s):  
TH Randle ◽  
TJ Cardwell ◽  
RJ Magee
Keyword(s):  
Electron Transfer ◽  
Chemical Reaction ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Reduction Mechanism ◽  
Ece Mechanism ◽  
Controlled Potential ◽  
Nickel Species ◽  
Electron Transfers ◽  
Potential Conditions

The reduction mechanism of a series of nickel(11) dithiocarbamates has been investigated in dimethyl sulphoxide at the mercury electrode. Under controlled-potential conditions, the reduction proceeds initially by an ECE mechanism (electron transfer-chemical reaction-electron transfer) with n = 1 for both electron transfers. The chemical reaction involves a dissociation to produce a nickel species more easily reduced than the nickel(11) dithiocarbamate. However, for some derivatives, rate constants for the chemical step show a time dependence, at electrolysis times above 5 s, consistent with an ECCE mechanism of the type where the product of the first chemical reaction reacts further to produce a nickel species more difficult to reduce than nickel(11) dithiocarbamate. Exhaustive reduction of nickel(11) diethyldithiocarbamate at the mercury-pool electrode gave non-integral n-values (2 > n > 1) consistent with the ECCE mechanism, and demonstrated that the product of the second chemical reaction is reoxidized to nickel(11) diethyldithiocarbamate by oxygen. The nature of the complete electrode reaction suggests a metal-centred reduction.

Electrochemical reduction of nickel(II) dithiocarboxylates at the mercury electrode

1997 ◽  
Vol 75 (7) ◽  
pp. 1023-1029 ◽  
Author(s):  
A. Safavi ◽  
L. Fotouhi
Keyword(s):  
Electron Transfer ◽  
Electrochemical Techniques ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Ece Mechanism ◽  
Reduction Mechanisms ◽  
Ec Mechanism ◽  
Controlled Potential ◽  
Electron Reduction ◽  
Derivatives Of

The reduction mechanisms of a series of nickel(II) dithiocarboxylate complexes have been investigated in dimethyl sulphoxide at the mercury electrode. Various electrochemical techniques, including polarography, cyclic voltammetry, chronoamperometry, and controlled potential coulometry, were employed. The reduction of the complexes of the acid derivatives of 2-aminocyclopentene-1-dithiocarboxylate (ACD) proceeds initially by an ECE mechanism (electron transfer – chemical reaction – electron transfer) followed by a one-electron irreversible process. The nature of the complete electrode reaction suggests a metal-centered reduction. The nickel complexes of the ester derivatives of ACD underwent a one-electron reduction that was subject to a follow-up catalytic reaction (EC′ mechanism) and the original complex is regenerated through this regeneration reaction. Keywords: reduction, nickel(II) dithiocarboxylate, mercury electrode.

scholarly journals Voltammetric studies of some azo compounds derived from 4-methyl-6,7-dihydroxy coumarin in microemulsion and aqueous media

2011 ◽  
Vol 7 (1) ◽  
pp. 1271-1279
Author(s):  
Omar A. Hazazi ◽  
Refat El-Sayed ◽  
El-Sayed. M. Mabrouk
Keyword(s):  
Reaction Pathway ◽  
Aqueous Media ◽  
Reduction Process ◽  
Electrode Reaction ◽  
Azo Compounds ◽  
Controlled Potential ◽  
Voltammetric Studies ◽  
Electron Reduction ◽  
Amine Compounds ◽  
Controlled Potential Coulometry

The cyclic voltammetric(CV) behavior of some azo compounds based on coumarin derivatives  was investigated in microemulsion systems and in aqueous solutions. The obtained results indicated that these compounds undergo an irreversible 4-electron reduction step leading to cleavage of the N=N center with the formation of amine compounds in all media. The effect of medium on the CV parameters was discussed. The total number of electrons involved in the reduction process was determined by controlled potential coulometry. Also, The effect of substituents on the electrode reaction pathway and the kinetic parameters of the electrode process were calculated and discussed. Based on the data obtained the electroreduction mechanism was suggested and discussed.

scholarly journals Electrochemical Investigation of Some Pharmaceutical Compounds at Mercury Electrode

2018 ◽  
Vol 34 (6) ◽  
pp. 2851-2858
Author(s):  
A. A. Al-Owais ◽  
I. S. El-Hallag
Keyword(s):  
Rate Constant ◽  
Digital Simulation ◽  
Supporting Electrolyte ◽  
Mercury Electrode ◽  
Simulation Method ◽  
Electrode Reaction ◽  
Cyclic Voltammograms ◽  
Triazole Derivatives ◽  
Aqueous Buffer ◽  
Electrochemical Parameters

The present work aims to report the investigation of the electrochemical behavior of 3- arylazomethine-1,2,4-triazole derivatives in universal aqueous buffer series at mercury electrode. The electrode behavior of the studied compounds was performed via voltammetric studies, chronoamperometry, convoluted transforms, and dp polarography techniques. The relevant chemical and electrochemical parameters of 3- aryl azomethine -1,2,4- triazole derivatives were determined experimentally in universal aqueous buffer series as supporting electrolyte at mercury electrode. CPC was used for determination of the number of electrons to elucidate the mechanistic pathway of electrode reaction of aryl azomethine triazole compounds. Digital simulation method was used to confirm the accuracy of the experimental chemical parameters (homogeneous chemical rate constant) and electrochemical parameters (heterogeneous rate constant, symmetry coefficient and redox potential) via matching between the experimental and theoretical cyclic voltammograms.

Electrochemical Dissolution of Goethite by Abrasive Stripping Voltammetry

1995 ◽  
Vol 60 (6) ◽  
pp. 950-959 ◽  
Author(s):  
Tomáš Grygar ◽  
Jan Šubrt ◽  
Jaroslav Boháček
Keyword(s):  
Solid Phase ◽  
Reaction Pathway ◽  
Stripping Voltammetry ◽  
Electrode Reaction ◽  
Reductive Dissolution ◽  
Quantitative Characterization ◽  
Acid Media ◽  
Qualitative And Quantitative ◽  
Spectroscopic Examination

Abrasive stripping voltammetry was applied to the investigation of the reductive dissolution of some iron(III) oxides and hydroxy-oxides, particularly goethite (α-FeOOH), in acid media. The electrode reaction directly involves the solid phase, and the reaction pathway depends on the phase composition and particle shape. This can be used for a qualitative and quantitative characterization of goethite. The results of a quantitative analysis of a mixture of goethite (α-FeOOH) and lepidocrocite (γ-FeOOH) are compared with those of IR and Moessbauer spectroscopic examination. The effects of the particle appearance (shape, crystal intergrowth) on the results of the voltammetric and chronoamperometric measurements are discussed.

Electrochemical studies of Schiff base compounds derived from antipyrine nucleus in ethanolic buffer solutions

2000 ◽  
Vol 78 (9) ◽  
pp. 1170-1177 ◽  
Author(s):  
Ibrahim S El-Hallag ◽  
Gad B El-Hefnawy ◽  
Youssef I Moharram ◽  
Enass M Ghoneim
Keyword(s):  
Schiff Base ◽  
Electrochemical Behaviour ◽  
Electrochemical Techniques ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Limiting Current ◽  
Electron Transfer Process ◽  
Buffer Solutions ◽  
Mechanistic Pathway ◽  
Electrochemical Parameters

The electrochemical behaviour of Schiff base compounds derived from an antipyrine nucleus was investigated in 30% (v/v) ethanolic buffer solutions (pH 3-11) using various electrochemical techniques at mercury electrode. The results showed that, the total limiting current of each of the studied compounds corresponds to 2-electron transfer process. The mechanistic pathway of the electrode reaction of the investigated compounds at mercury electrode, the effect of the medium, and the evaluation of the electrode reaction parameters were illustrated and discussed.Key words: Schiff base, antipyrine nucleus, electrode reaction, electrochemical parameters, cyclic voltammetry.

Chelating Tendencies of Some N-(2-Acetyl-1,3-Indandione) Trialkyl Ammonium Iodides with Transition Metal Ions

1973 ◽  
Vol 28 (5-6) ◽  
pp. 317-318 ◽  
Author(s):  
M. K. Bachlaus ◽  
K. L. Menaria ◽  
P. Nath
Keyword(s):  
Free Energy ◽  
Complex Formation ◽  
Transition Metal ◽  
Copper Complex ◽  
Dissociation Constants ◽  
Transition Metal Ions ◽  
Iron Complex ◽  
Potentiometric Studies ◽  
Kcal Mole ◽  
The Stability

The ligands T.P.A.I.* and T.B.A.I.** have been synthesised and their dissociation constants are 1.738 · 10-10 and 1.412 · 10-8 respectively. The potentiometric studies show that these reagents form 1 : 1 complex with copper(II) and iron(II). The stability constants of copper complex and iron complex with T.P.A.I. are 6.43 and 6.51 respectively and for T.B.A.I. 4.36 and 4.24 respectively. The free energy of complex formation at 25°C are 8.76 Kcal/mole and 8.87 Kcal/mole for Cu (II)-T.P.A.I. and Fe (II)-T.P.A.I. respectively, whereas the free energy of the Cu (II)-T.B.A.I. and Fe(II)-T.B.A.I. are 5.94 Kcal/mole and 5.78 Kcal/mole respectively.

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