• Title/Summary/Keyword: Polarography

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Enhanced Electrochemifluorescence and Reduction Mechanism of Acetoxy Coumarin Derivatives in Acetonitrile Solution

  • Kim, Sung-Hyun;Jung, Eun-Joo;So, Eun-Mi;Shen, Chang-Zhe;Chun, Hyun-Ja;Kim, Young-Man;Kim, Il-Kwang
    • Bulletin of the Korean Chemical Society
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    • v.27 no.9
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    • pp.1329-1334
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    • 2006
  • The electrochemical reduction of coumarin, 7-acetoxy-4-methyl coumarin (AMC), and 7-acetoxy-4-bromomethyl coumarin (ABMC), in 0.1 M tetraethyl ammonium perchlorate/acetonitrile solution was carried out by direct current, differential pulse polarography, cyclic voltammetry, and controlled potential coulometry. The electrochemical reduction of ABMC was proceeded through three steps of electron transfer coupled with the chemical reactions. The color of solution was changed to yellow when the carbonyl group was reduced during 2nd step (-1.8 volts) and independented with cleavage of bromo group. Highest fluorescence intensity showed when the electrochemical reduction of AMC was controlled at near the potential (-2.3 volts vs. Ag/AgCl).

Enhancement of Fluorescent Properties and Electrochemical Reduction of Coumarin Derivatives (Coumarin 유도체들의 전기화학적 환원과 형광성의 증강)

  • Chun, Hyun Ja;Kim, Sung Hyun;Jung, Eun Joo;Lee, Hye Suk;Kim, Il Kwang
    • Analytical Science and Technology
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    • v.18 no.1
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    • pp.89-95
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    • 2005
  • Studies on the electrochemical reduction of 7-acetoxy-4-bromomethyl-coumarin (ABMC), 7-acetoxymethyl coumarin (AMC), and coumarin in 0.1 M tetraethyl ammonium perchlorate acetonitrile solution were carried out with direct current, differential pulse polarography, cyclic voltammetry, and controlled potential coulometry. The electrochemical reduction of ABMC was proceeded through three irreversible steps coupled with the chemical reactions. The solution color was changed to yellow when the carbonyl group was reduced during second step and the color change was independent with bromo group of ABMC. Fluorescent intensity was highest when the electrochemical reduction was controlled at near the overpotential of supporting electrolyte (-2.3 volts).

Electro-Catalytic Hydrogenation and the Electrode Reaction Mechanism of the Carbon-6-Bromo groups of 6,6-Dibromopenicillanic acid 1,1-Dioxide (6,6-Dibromopenicillanic acid 1,1-Dioxide 분자내 탄소 6-위치 브롬기의 전극촉매 수소화반응과 전극반응기구)

  • Il Kwang Kim;Young Haeng Lee;Chai Ho Lee
    • Journal of the Korean Chemical Society
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    • v.35 no.2
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    • pp.165-171
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    • 1991
  • The electrochemical reduction of carbon-6-dibromo groups on 6,6-dibromo penicillanic acid 1,1-oxide(DBPA) was investigated by direct current, differential pulse polarography, cyclic voltammetry and controlled potential coulometry. The irreversible two electrons transfer on the reductive debromination of each bromo group proceeded by EC,EC mechanism at the two electrode reduction steps(-0.48, -1.62 volts). The 6-bromo-PA and 6,6-dihydro-PA was synthesized by controlled potential electrolysis. Upon the basis of results on the products analysis and interpretation of polarograms obtained at various pH, electrochemical reaction mechanism was suggested.

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Electrochemical Reduction of 0,0-Dimethyl-0-(3-Methyl-4-Nitrophenyl)-phosphorothioate(Sumithion®) in Acetonitrile Solution (Acetonitrile 용액중(溶液中)에서 0,0-Dimethyl-0-(3-Methyl-4-Nitrophenyl)-phosphorothioate(Sumithion®)의 전기화학적(電氣化學的) 환원반응(還元反應))

  • Park, Seung Heui;Sung, Nack Do
    • Korean Journal of Agricultural Science
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    • v.11 no.2
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    • pp.315-321
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    • 1984
  • The electrochemical reduction of 0,0-dimethyl-0-(3-methyl-4 -nitrophenyl)-phosphorothioate ($Sumithion^{(R)}$) in acetonitrile solution has been studied by direct current (DC), differential pulse (DP) polarography and cyclic voltammetry methods. The irreversible electron-transfer chemical reaction (EC) mechanism of Sumithion proceeds by six electron-transfer to form radical and reduction of three-step which undergoes single bond of the phosphorus atom & phenoxy group by electron-transfer and protonation cleaved to give p-hydroxyamino-m-cresol and dimethylthiophosphonate as major product.

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Electrochemical Study on the 3-Phenyl-4-Nitrosydnone (3-Phenyl-4-Nitrosydnone의 전기화학적 연구)

  • Il-Kwang Kim;Youn-Geun Kim;Soon-Jong Han
    • Journal of the Korean Chemical Society
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    • v.32 no.3
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    • pp.195-202
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    • 1988
  • An electrochemical reduction on the 3-phenyl-4-nitrosydnone in acetonitrile solution has been studied by direct current, differential pulse polarography, cyclic voltammetry and controlled potential coulometry. Before the cleavage of phenyl-N single bond a irreversible electron transfer-chemical reaction(EC) mechanism of nitro functional group proceeded to form amino (or-hydroxylamino) group by multielectron transfer which is followed to give phenyl hydrazine by single electron transfer-chemical reaction at the 2nd and 3rd irreversible reduction wave of high negative potential region. The cathodic half-wave potentials shown to be shift negative due to inhibitory effect of cetyl-trimethyl ammonium bromide micelle while reversible anodic peaks on the 2nd and 3rd reduction waves in the presence of NaLS at high negative potential region.

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Studies on the Polarographic Behavior of Elemental Sulfur (원소 유황의 Polarograph 거동에 관한 연구)

  • 김준용;장순자
    • YAKHAK HOEJI
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    • v.22 no.4
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    • pp.201-206
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    • 1978
  • The analysis of elemental sulfur by polarography has already been reported in the literature. Only a discussion of the more important factors influencing the analysis is here presented. (1) The effects of pH on the reduction of elemental sulfur are pronounced and the use of buffered solutions for the analysis of elemental sulfur is necessary. The authors found that a pH of 4-6 was found to be reproducible polarograms by use of D.C. polarograph. However, in alkali solvents the plateau of elemental sulfur has a pronounced dip if the concentration of sulfur is as much as 30ppm. (2) A.C. polarographic method shows a very high sensitivity in the case of sulfur reduction, so that the very low concentration of sulfur can easily be determined (about 1ppm). (3) The characteristics of sulfur wave can be formulated according to Stackelberg-Hauck-Hans equation. It was found that the curve of the peak potential of elemental sulfur in A.C. polarography versus logarithm of sulfur concentration was obtained to be straight line with the slope of 29.6 millivolts. This result was well agreed with theoretical consideration. (4) It was assumed that this polarographical methods were applicable to micro-analysis of elemental sulfur in crude oil and its petrochemical products, precipitated sulfur, and sulfur ointments with accuracy and rapidity.

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Determination of Rhodium by Differential Pulse Polarography (펄스차이 폴라로그래피를 이용한 로듐의 정량)

  • Kwon, Young-Soon;Hong, Mi-Jeong;Czae, Myung-Zoon
    • Analytical Science and Technology
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    • v.13 no.1
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    • pp.1-4
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    • 2000
  • Determination of trace rhodium, based on catalytic reduction of protons by the adsorbed Rhformaldehyde complexes formed in formaldehyde-hydrochloric acid medium, was demonstrated. The condition for the measurements of Rh at trace levels was 0.004%(w/v) formaldehyde-0.75M hydrochloric acid. In this medium detection limit was $7.0{\times}10^{-12}M$ and the linear dynamic range was $1.0{\times}10^{-11}{\sim}1.0{\times}10^{-8}M$ Rh. There were no interferences from other platinum group metal ions even in the presence of a 500-fold excess.

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Evaluation of the Function exp$(x^2)$ erfc(x) to Higher Precisions for Higher Order Derivative Polarography of CE-type Electrode Process

  • Kim, Myung-Hoon;Smith, Veriti P.;Hong, Tae-Kee
    • Bulletin of the Korean Chemical Society
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    • v.11 no.6
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    • pp.497-505
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    • 1990
  • The function exp$(x^2)$erfc(x), which is often encountered in studies of electrode kinetics, is evaluated to an extended precision with 32 significant decimal digits in order to find theoretical relationships used in derivative polarography/voltammetry for a chemically-coupled electrode process. Computations with a lower precision are not successful. Evaluation of the function is accomplished by using three types of expansions for the function. Best ranges of arguments are selected for each equation for particular precisions for efficiencies. The method is successfully applied to calculate higher-order derivatives of the current-potential curves in all potential ranges for a reversible electron transfer reaction coupled with a prior chemical equilibrium (i.e., a CE type process). Various parameters that characterize the peak asymmetry (such as ratios of peak-heights, ratios of half-peak-widths, and separations in peak-potentials) are analyzed to find how kinetic and thermodynamic parameters influence shapes of the derivatives. The results from the CE process is compared with those from an EC process in which a reversible electron transfer is coupled with a follow-up homogeneous chemical reaction. The two processes exibit quite contrasting differences for values of the parameters.

Stoichiometry and Stability of Complexes Formed between 18-Crown-6 as well as Digenzo-18-Crown-6 Ligands and a Few Metal Ions in Some Non-aqueous Binary Systems Using Square Wave Polarography

  • A. Nezhadali, Gh. Rounaghi;M. Chamasaz
    • Bulletin of the Korean Chemical Society
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    • v.21 no.7
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    • pp.685-689
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    • 2000
  • The complexation reaction between Pb2+,TI and Cd2+ions and macrocyclic ligands, 18-crown-6 ( 18C6) and dibenzo- 18-crown-6 (DB 18C6), was studied in dimethylsulfoxide (DMSO)-nitromethane (NM) and dimethyl-formamide (DMF)-nitromethane binary system s by square wave polarography (SWP) technique. The stoichiometry and stability of the complexes were determined by monitoring the shifts in half-waves or peak potentials of the polarographic waves of metal ions against the Iigand concentration. In most cases, the stability constants of complexes increase with increasing amounts of the nitromethane in mixed binary solvents used in this study. The complexes formed between 18C6 and DB18C6 and these metal cations in all cases had a stoichiometry of 1 : 1. The results obtained show that there is an inverse relationship between the formation constant of complexes and the donor number of solvents based on a Gatmann donocity scale and the stability constants show a high sensitivity to the composition of the mixed solvent systems. A linear behavior was observed for variation of log Kf of I8C6 complexes vs the composition of the mixed solvent systems in NM/DMSO and NM/DMF,but a non-linear behavior was observed in the case of DB 18C6 complexes in these binary systems. In most of the systems investigated, the Pb2+ cation forms a more stable complex with the 18C6 than other two cations and the order of selectivity of this Iigand for cations is: Pb2+ > TI+,Cd2+.

Electrochemical Studies on $Sm^3+$-ARS Complexes ($Sm^3+$-ARS착물의 전기화학적 연구)

  • Son, Byoung-Chan
    • The Journal of Natural Sciences
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    • v.11 no.1
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    • pp.33-39
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    • 1999
  • Electrochemical behaviors of $Sm^3+$-ARS complexes has been investigated by d.c.polarography, differential pulse polarography and cyclic voltammetry. $Sm^3+$forms 1 : 3 adsorptive complexes with ARS.The reduction potential of complex wave $(P_2)$ shifted more negatively than the ligand wave $(P_1)$. The linear calibration curves of decreasing $P_1$ and increasing $P_2$ is obtained when $Sm^3+$ concentration varies from TEX>$2{\times}10^{-6}$ M to $3.2{\times}10^{-5}$ M.

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