Half a Century of Research Using Polarography

Zuman, P.

doi:10.1006/mchj.1997.1468

Cited by 25 publications

(19 citation statements)

References 223 publications

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“…3) which is a behavior similar to that usually observed for hydrazones and Schiff bases in alkaline media [25]. This behavior was attributed to the protonation of the reactant species which occurs as a homogeneous process at the electrode surface where the limiting current is controlled by the rate of protonation [25]. An analysis of the irreversible polarographic wave of for each of the examined compounds was done by plotting E d.e versus log (i/i l − i) [24].…”

Section: Voltammetric Studiessupporting

confidence: 79%

“…The limiting current (i 1 ) of the examined Schiff bases (SDSB, SASB and SGSB) was pH independent in solutions of pH < 7.5 while at higher pH values the limiting current of all the examined compounds decreased with an increase of the pH of the medium (Fig. 3) which is a behavior similar to that usually observed for hydrazones and Schiff bases in alkaline media [25]. This behavior was attributed to the protonation of the reactant species which occurs as a homogeneous process at the electrode surface where the limiting current is controlled by the rate of protonation [25].…”

Section: Voltammetric Studiessupporting

confidence: 71%

“…The E 1/2 -pH plots of the compounds are straight lines with the slope values of S 2 , {S 2 , mV = (59/αn a )P } also reported in Table 1. The number of protons P participating in the rate-determining step of the reduction process was calculated from the following relation [24][25][26][27] and was found to be equal to one (Table 1).…”

Section: Voltammetric Studiesmentioning

confidence: 99%

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

et al. 2007

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Abstract:The 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 -CH 2 -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 (Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ ) were determined potentiometrically at room temperature.

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Section: Voltammetric Studiessupporting

confidence: 79%

Section: Voltammetric Studiessupporting

confidence: 71%

Section: Voltammetric Studiesmentioning

confidence: 99%

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

et al. 2007

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“…Theoretically, the nitro group can receive up to six electrons in the complete reduction to the amine derivative. 9,18 Under anaerobic conditions or low oxygen pressure, the reduction process is similar to that observed for nitrobenzene. 18 A total of two electrons and two protons is involved in the formation of the nitroso (R-NO) intermediate, two more electrons and protons result in the hydroxylamine (R-NHOH): 13,14,18 R-NO 2 + e -R-NO 2 • ¯(1) R-NO 2 • ¯ + 2H…”

Section: Introductionmentioning

confidence: 52%

Voltammetric behavior of nitrofurazone and its hydroxymethyl prodrug with potential anti-Chagas activity

La-Scalea¹,

Menezes²,

Julião³

et al. 2005

J. Braz. Chem. Soc.

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A doença de Chagas é um grave problema de saúde pública para a América Latina, situação agravada pela inexistência de quimioterapia eficiente. Os dois fármacos comercialmente encontrados, benznidazol e nifurtimox, são eficazes apenas na fase aguda da doença. A nitrofurazona é ativa contra Trypanosoma cruzi, entretanto, a alta toxicidade impede seu uso na parasitose. A hidroximetilnitrofurazona é um pró-fármaco da nitrofurazona, que apresenta maior atividade contra Trypanosoma cruzi, além de ser menos tóxico. Estudou-se o comportamento voltamétrico da nitrofurazona por voltametria cíclica, varredura linear e pulso diferencial, comparando-o ao do metronidazol e do cloranfenicol. Os coeficientes de difusão dos três fármacos foram estimados aplicando-se a equação de Wilke-Chang. Este artigo também apresenta o estudo do derivado hidroximetilnitrofurazona por voltametria cíclica. A redução de nitrofurazona é pH-dependente e em meio ácido o derivado hidroxilamínico, envolvendo quatro elétrons, é o principal produto formado. Em meio alcalino e com prévio tratamento do eletrodo de carbono vítreo, a redução de nitrofurazona ocorre em duas etapas: a primeira envolve um elétron para formar o nitro-radical aniônico e a segunda etapa corresponde à formação da hidroxilamina. Hidroximetilnitrofurazona possui comportamento voltamétrico semelhante e, de forma análoga, apresentou a mesma eletroatividade e capacidade de estabilização do nitro-radical, indicando que a modificação molecular de nitrofurazona não introduziu alterações no seu comportamento voltamétrico. Uma breve discussão das diferenças de atividade biológica entre os compostos também é apresentada.Chagas' disease is a serious health problem for Latin America. The situation is worsened by the lack of efficient chemotherapy. The two available commercial drugs, benznidazole and nifurtimox, are more effective in the acute phase of the disease. Nitrofurazone is active against Trypanosoma cruzi, however its high toxicity precludes its current use in parasitosis. Hydroxymethylnitrofurazone is a prodrug of nitrofurazone. It is more active against Trypanosoma cruzi than nitrofurazone, besides being less toxic. This work shows the voltammetric behavior of nitrofurazone and a comparison with those of metronidazole and chloramphenicol using cyclic, linear sweep and differential pulse voltammetries. For these drugs also the prediction of the diffusion coefficients using Wilke-Chang equation was performed. The reduction of nitrofurazone is pH-dependent and in acidic medium the hydroxylamine derivative, involving four electrons, is the principal product formed. In aqueousalkaline medium and with a glassy carbon electrode pre-treatment the reduction of nitrofurazone occurs in two steps, the first involving one electron to form the nitro-radical anion and the second corresponding to the hydroxylamine derivative formation. Hydroxymethylnitrofurazone presented the same voltammetric behavior and electroactivity, indicating that the molecular modification performed in nitrofurazone did no...

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“…T h e s y n t h e s i z e d 2 -m e t h y l -4 -( 2 -h y d r o x y -5-nitrophenylazo)-quinoline (3) was also reduced at the mercury electrode in buffered solution of pH values 2-10 in a single 8-electron step, which is attributed to reduction of either the -N=N-double bond to the amine stage and the -NO 2 group to the hydroxylamine stage, via the consumption of four electrons for each centre, 24,35 (Scheme 4, reaction 4). At pH values higher than 10, this reduction step splits into two steps.…”

Section: Electrode Reaction Of Azo-derivative (3)mentioning

confidence: 99%

Synthesis, electrochemical, spectrophotometric and potentiometric studies of two azo-compounds derived from 4-amino-2-methylquinoline in ethanolic-aqueous buffered solutions

El-Attar¹,

Ismail²,

Ghoneim³

2012

J. Braz. Chem. Soc.

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da 4-amino-2-metilquinolina foram sintetizados. Suas estruturas químicas foram caracterizadas e confirmadas através de análise elementar, espectroscopia no infravermelho (IR), ressonância magnética nuclear (RMN) de 1 H e espectrometria de massas (MS). O comportamento eletroquímico do composto de partida (4-amino-2-metilquinolina) e dos dois azo-derivativos sintetizados foi estudado com um eletrodo de mercúrio em solução tampão universal B-R em diferentes valores de pH (2-11,5) contendo etanol 40% (v/v) usando polarografia dc, voltametria cíclica e coulometria com potencial controlado. Os caminhos de reação dos compostos no eletrodo foram elucidados e são discutidos. As constantes de dissociação (pKa) dos compostos examinados, constantes de estabilidade e estequiometria dos complexos formados em soluções dos compostos com alguns íons de metais de transição (Co(II), Ni(II), Cu(II), La(III) and UO 2 2+ ) foram determinadas.Two azo-compounds, 2-methyl-4-(5-amino-2-hydroxy-phenylazo)-quinoline (2) and 2-methyl-4-(2-hydroxy-5-nitrophenylazo)-quinoline, derived from 4-amino-2-methylquinoline were synthesized. Their chemical structures were characterized and confirmed by means of elemental chemical analysis, infrared (IR) spectroscopy, 1 H nuclear magnetic resonance (NMR) and mass spectrometry (MS). The electrochemical behavior of the starting compound (4-amino-2-methylquinoline) and of the two synthesized azo-derivatives was studied at the mercury electrode in the B-R universal buffer at various pH values (2-11.5) containing 40% (v/v) ethanol using dc-polarography, cyclic voltammetry and controlled-potential coulometry. Their electrode reaction pathways were elucidated and discussed. The dissociation constants (pKa) of the examined compounds, stability constants and stoichiometry of their complexes in solution with some transition metal ions (Co(II), Ni(II), Cu(II), La(III) and UO 2 2+ ) were determined.

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Half a Century of Research Using Polarography

Cited by 25 publications

References 223 publications

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

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

Voltammetric behavior of nitrofurazone and its hydroxymethyl prodrug with potential anti-Chagas activity

Synthesis, electrochemical, spectrophotometric and potentiometric studies of two azo-compounds derived from 4-amino-2-methylquinoline in ethanolic-aqueous buffered solutions

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