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.

scholarly journals Electrochemical Behaviour of N′-(p-toluenesulphonyl)-3-methyl-4-(4′-substituted arylhydrazono) pyrazolin-5-ones

2012 ◽  
Vol 9 (4) ◽  
pp. 1864-1874
Author(s):  
V. Nagaraju ◽  
R. Sreenivasulu ◽  
P. Venkata Ramana
Keyword(s):  
Electrochemical Behaviour ◽  
Reduction Process ◽  
Effect Of Solvent ◽  
Buffer Solutions ◽  
Diffusion Controlled ◽  
Controlled Potential Electrolysis ◽  
Dc Polarography ◽  
Controlled Potential ◽  
Ph Range ◽  
And Diffusion

The electrochemical behaviour of N′-(p-toluenesulphonyl)-3-methyl-4-(4′-substituted arylhydrazono) pyrazolin-5-ones has been investigated at dme and gc electrodes in buffer solutions of pH 2.0, 4.0, 6.0, 8.0 and 10.0 using dc polarography and cyclic voltammetry and coulometry. The compounds exhibit one well defined wave in the entire pH range of study. The process is irreversible and diffusion controlled. Controlled potential electrolysis indicates the involvement of four electrons in the reduction process. The effect of solvent, cations and anions, temperature and substitutents on the mechanism of reduction has been studied. Based on the results obtained the mechanism of reduction has been suggested.

scholarly journals Differential Pulse Polarographic Determination of Procymidone in Formulations and Wine

2002 ◽  
Vol 85 (3) ◽  
pp. 731-735 ◽  
Author(s):  
Neelam Y Sreedhar ◽  
Thommandru R Babu ◽  
Kethamreddy Samatha ◽  
Devarapalli Sujatha ◽  
Thenepalli Thriveni
Keyword(s):  
Reduction Process ◽  
Differential Pulse ◽  
Differential Pulse Polarography ◽  
Experimental Conditions ◽  
Controlled Potential Electrolysis ◽  
Pulse Polarography ◽  
Half Wave ◽  
Single Well ◽  
Controlled Potential ◽  
Ph Range

Abstract The dicarboximide fungicide procymidone was studied systematically by using direct current polarography, cyclic voltammetry, differential pulse polarography (DPP), controlled potential electrolysis, and millicoulometry in the universal buffer medium with dimethylformamide as the solvent. Procymidone exhibited a single well-defined polarographic wave in the pH range 2.0–6.0, leading to the formation of the hydroxy compound. The overall reduction process was diffusion-controlled and adsorption-free. The variation of half-wave potential with pH, the concentration of the analyte, and other experimental conditions are described. The reduction mechanism proposed is an overall 4-electron process, in which the dicarboximide group is reduced. DPP was used to determine procymidone in agricultural formulations and wine at the optimum conditions found; a detection limit of 2.4 × 10−9M was estimated. The results obtained by the proposed method were also compared with those obtained by other methods.

The electrochemical oxidation of 2,5-dihydroxybenzoic acid on a mercury electrode in aqueous solutions

1986 ◽  
Vol 64 (1) ◽  
pp. 11-14 ◽  
Author(s):  
D. Sazou ◽  
N. Papadopoulos
Keyword(s):  
Oxidation Process ◽  
Electrochemical Behaviour ◽  
Mercury Electrode ◽  
The Other ◽  
Hanging Mercury Drop Electrode ◽  
Dihydroxybenzoic Acid ◽  
Current Function ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Ph Range

The electrochemical behaviour of 2,5-dihydroxybenzoic acid (2,5-DHBA) has been studied in the pH range 5.5–12.7 at a hanging mercury drop electrode (HMDE). Voltammograms show the existence of one reversible wave of 2,5-DHBA governed by diffusion conditions. In the oxidation process a two-electron transfer takes place, as shown by the controlled potential electrolysis. From the calculation of the voltammetric parameters (peak width Ep − Ep/2, peak current function [Formula: see text]and from the other experimental data, a mechanism for the overall reaction in two different pH ranges, 5.5–9.5 and 9.5–12, is proposed.

Derivatization of polyoxotungstates in aqueous solution. Exploration of the kinetic stability of cobalt(II)- and cobalt(III) derivatives of lacunary anions with pyridine and pyridine-type ligands

2001 ◽  
Vol 79 (5-6) ◽  
pp. 802-808 ◽  
Author(s):  
Joseph L Samonte ◽  
Michael T Pope
Keyword(s):  
Aqueous Solution ◽  
Isonicotinic Acid ◽  
Ligand Substitution ◽  
Water Ligand ◽  
H Nmr ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Cesium Salts ◽  
Line Widths ◽  
Derivatives Of

Four complexes of cobalt(II) with lacunary polyoxotungstate ligands, α-[PW11O39Co(H2O)]5-, α-[SiW11O39Co(H2O)]6-, α1-, and α2-[P2W17O61Co(H2O)]8- have been examined as potential precursors to substitutionally inert derivatized polytungstates that are stable in aqueous solution at near neutral pH. Replacement of the terminal water ligand by pyridine is readily achieved and the rates of exchange between bound and free pyridine were determined from NMR line widths at temperatures between 24 and 48°C. Oxidation to the aquacobalt(III) and pyridinecobalt(III) polytungstates occurs at potentials between +0.64 V (for α1-P2W17O61Co(py)]8-) and +1.00 V (for α2-[P2W17O61Co(H2O)]8-). The cobalt(III) complexes (with the exception of α-[PW11O39Co(H2O)]4- which undergoes slow reduction by the solvent) were prepared by controlled potential electrolysis and by oxidation with potassium perdisulfate. The rates of pyridine substitution on the aquacobalt(III) complexes were determined and follow the sequence α1-[P2W17O61Co(H2O)]7- (~0.5 M-1 s-1) » α2-[P2W17O61Co(H2O)]7- ~ α-[SiW11O39Co(H2O)]5-. Cesium salts of α1-[P2W17O61CoIII(L)]7- (L = pyrazine, 4,4′-bipyridine, isonicotinic acid, and the ethyl ester of isonicotinoylglycylglycine) and the "dumbbell" 2:1 complex with bridging 4,4′-bipyridine were isolated and characterized by cyclic voltammetry and 1H NMR spectroscopy.Key words: lacunary polyoxotungstates, cobalt, ligand substitution, kinetics, redox.

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.

VOLTAMMETRIC DETERMINATION OF ACETOPHOS IN WATER SAMPLES AT CNTPE

2013 ◽  
Vol 12 (03) ◽  
pp. 1350018
Author(s):  
SARVAREDDY RAJASEKHAR REDDY ◽  
T. RAVEENDRANATH BABU
Keyword(s):  
Water Samples ◽  
Supporting Electrolyte ◽  
Reduction Process ◽  
Standard Addition ◽  
Differential Pulse ◽  
Experimental Conditions ◽  
Controlled Potential Electrolysis ◽  
Universal Buffer ◽  
Controlled Potential ◽  
Ph Range

In this paper, a sensitive differential pulse voltammetric method to determine the residues of acetophos in water samples at CNTPE were reported. The significance of CNTPE is to result in low detection limits, high sensitivities, reduction of over-potentials, high mechanical strength and high conductivity and resistance to surface fouling. The universal buffer with pH range 2.0–6.0 is used as supporting electrolyte. Cyclic voltammetry employed to evaluate electrode mechanism and number of electrons involved in reduction process were found out by using Millicoulometry and the product collected by applying Controlled potential electrolysis. Experimental conditions such as accumulation potential, accumulation time and scan rate were optimized. Calculations were made by standard addition method.

AFM and SEM Characterization of Chemically Modified Electrodes Based on 5-[(azulen-1-yl) methylene]-2-thioxothiazolidin-4-one

2018 ◽  
Vol 68 (12) ◽  
pp. 2799-2803
Author(s):  
Maria Daniela Pop ◽  
Oana Brincoveanu ◽  
Mihaela Cristea ◽  
George Octavian Buica ◽  
Marius Enachescu ◽  
...  
Keyword(s):  
Glassy Carbon ◽  
Roughness Parameter ◽  
Modified Electrodes ◽  
Chemically Modified Electrodes ◽  
Adhesion Properties ◽  
Chemically Modified ◽  
Controlled Potential ◽  
Constant Potential ◽  
Metal Ions Detection

Preparation and microscopy characterization of polymer modified glassy carbon electrodes based on (5-[(azulen-1-yl) methylene]-2-thioxothiazolidin-4-one (L) were reported. Atomic Force Microscopy was used to investigate the morphological and mechanical properties of the deposited polyL films onto glassy carbon. The topography images of the analyzed samples exhibited the presence of some columnar shape features onto the layer surfaces. The surface roughness of the layers deposited at constant charge calculated from topography images, increased with the more positive applied potential for controlled potential electrolysis. At different charges, the roughness parameter showed the same behavior for the layers obtained applying a constant potential without having a noticeable influence on the adhesion properties on the substrate. Analysis using scanning electron microscopy shows a relatively uniform surface arrangement of the polymer and the presence of some clusters which are disturbing the planarity. PolyL chemically modified electrodes have been used for heavy metal ions detection with best results for lead.

Adsorption of Benzene from Aqueous Solution Using Base Modified Expanded Perlite

2012 ◽  
Vol 622-623 ◽  
pp. 1779-1783
Author(s):  
Richard Appiah-Ntiamoah ◽  
Xuan Thang Mai ◽  
Francis W.Y. Momade ◽  
Hern Kim
Keyword(s):  
Zeta Potential ◽  
Adsorption Capacity ◽  
Linear Regression Analysis ◽  
Basic Medium ◽  
Maximum Adsorption Capacity ◽  
Hydroxyl Groups ◽  
Expanded Perlite ◽  
Oh Groups ◽  
Base Solution ◽  
Ph Range

In this study, the adsorption capacity of expanded perlite (EP) for benzene at low concentrations in water was investigated after EP was treated with sodium hydroxide (NaOH). IR spectra used to characterize the modified EP showed that there was no bonding between NaOH and the hydroxyl groups on the surface of EP. However, the NaOH provided a basic medium for negatively charged surface oxide ions (-SO-) to form on EP. This fact was corroborated by pH readings of the modification solution. This reduced in pH from 10 to 9 at the end of the reaction which indicated that the hydroxyl OH- groups on the EP underwent deprotonation and hence releases H+ into the solution, and also positive sites on EP adsorbed OH- ions from the base solution. Mahir et al. in their paper Zeta potential of unexpanded and expanded perlite samples in various electrolyte media confirmed that EP has no isoelectric point and exhibits negative zeta potential in the pH range of 2-11. The surface oxides (-SO-) were believed to have given EP it adsorptive potential. Adsorption isotherm values correlated reasonably well with the Langmuir isotherm model and it parameters (qo and K) were obtained using linear regression analysis. A maximum adsorption capacity (qo) value of 19.42 mg/g was achieved.

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