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1

Adenine adsorption in different pH acetate buffer

Gugała-Fekner Dorota

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 2

art. no. 144446

EN

The research results facilitate the description of adenine adsorption on the mercury electrode with reference to the pH of the supporting electrolyte which was the acetate buffer with pH of 3, 4, 5 and 6. The thermodynamic analysis indicates that the curves of the differential capacity of the studied systems with adenine do not overlap with the curves for the supporting electrolyte – the acetate buffer. This indicates the occurrence of adsorption of the studied compound on the mercury electrode within the whole range of applied concentrations in the case of every tested pH value of the acetate buffer. Adsorption energy and interaction constants were determined using the Frumkin isotherm and the viral isotherm. It was demonstrated that a adenine molecule is adsorbed on the mercury electrode in a buffer with pH 4, 5 and 6 through the negative pole, whereas in a buffer with pH 3 through the positive pole. Physical adsorption was observed in the studied systems. This is indicated by the occurrence of a typical maximum on the curve of the relation the relative surface excess amounts and the potential of the electrode; crossed curves of the following relation surface charge of the electrode from its potential (surface charge of the electrode from its potential σ = f(E)) at one point and, thus, the possibility of determining electrical parameters characterizing maximum adsorption as well as the absence of linearity of the function free energy of adsorption as a function of electrode potential ∆G0 = f(E).

2

Elektroutlenianie i elektroredukcja barwnika reaktywnego Reactive Yellow 3

Chrześcijańska E., Kuśmierek E.

Przemysł Chemiczny

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2010

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T. 89, nr 9

1200-1204

3

The effect of cathode materials on the electrochemical reduction of nitric acid

Vasudevan D.

Polish Journal of Chemical Technology

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2010

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Vol. 12, nr 1

35-37

EN

Electrochemical or chemical reduction of nitric acid is a well studied area in literature due to the importance of the products formed. The present work focuses on the effect of conventional cathode materials including PbO2, amalgamated Cu, graphite, Pb, Pt and a modified electrode material Ti/TiO2 on the reduction of nitric acid. Ammonia and hydroxylamine are the main products which are estimated by conventional titration methods. Other conditions being similar, the product distribution varies quite drastically as a function of the electrode material and Ti/TiO2 is found to favor a higher ratio of hydroxylamine to ammonia formation compared to other electrodes. The conditions have also been optimized based on the maximum yield of the product.

4

Voltammetric study of the Reduction of Triptindanones in N,N-Dimethylformamide

Jaworski J., Kuck D.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 9

1597-1604

EN

The mechanism of electroreduction of 9-triptindanone (1), 9,10-triptindanedione (2), and 9,10,11-triptindanetrione (3) was studied by use of the cyclic voltammetric method. All carbonyl groups were reduced giving one, two, and three one-electron cathodic peaks for 1, 2, and 3, respectively and the corresponding oxidation peaks. The first electron transfer is reversible and the radical anions formed are stable. Additional small peaks for 2 and 3 were discussed in terms of an adsorption of reactants and intermediates and their reactions with the participation of supporting electrolyte cations as well as the residual water.

5

Elektrochemiczne właściwości platyny i palladu osadzonych na polianilinie w redukcji związków chloroorganicznych

Wzorek B., Kurek S. S., Stokłosa A.

Czasopismo Techniczne. Chemia

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2004

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R. 101, z. 1-Ch

155-168

PL

Celem prezentowanej pracy bylo zbadanie elektrokatalicznych właściwości elektrod platynowych i palladowych osadzonych na polianilinie. Elektrody polimerowe modyfikowane metalem były zastosowane w procesach elektrochemicznej redukcji chlorowcopochodnych organicznych. We wszystkich procesach stosowano woltamperometrię cykliczna. Na woltamogramach redukcji heksachlorobenzenu, tetrachlorometanu, chloroformu widoczne są nieodwracalne fale. Kale katodowe uzyskane na elektrodach modyfikowanych w stosunku do elektrod z litego metalu są przesunięte w stronę bardziej dodatnich potencjałów. W pracy pokazano, że elektrody polimerowe modyfikowane metalem mają wyższą aktywność elektrokatalityczną niż elektrody z litego metalu.

EN

The aim of the present work was to investigate the electrocatalytic properties of polyaniline modified by platinum and palladinum. The metal-modified polymer electrodes were applied as cathodes for electrochemical reduction of chloroorganic compounds in DMF. All electrochemical processes were studied using cyclic voltammetry. Cyclic voltammograms for the reduction of hexachlorobenzene, tetrachloromethane, chloroform show irreversible waves. The first and second waves of the reduction of hexachlorobenzene and tetrachloromethane on modified electrodes are shifted to more positive potentials with metal microcrystals demonstrate higher electrocatalytic activity than bulk metal electrodes.

6

Substituent effects on reduction of some 3,6-disubstituted-4-amino- l,2,4-triazin-5-(4H)-ones

Ludvík J., Riedl F., Urban J., Zuman P.

Chemia Analityczna

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2004

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Vol. 49, No. 6

777-792

EN

In all studied 4-amino-1,2,4-triazin-5-ones the 1,6-C=N bond is electrochemically reduced at potentials by about 0.5 V more positive than the bond 2,3-N=C in these compounds. The reduction of the protonated form of the 1,6-C=N bond occurs in 3-methyl-6-phenyl (I), 3-methylmercapto-6-tert.-butyl (II) and 3-methyl-6-tert.-butyl (V) derivatives in a single twoelectron step, whereas in the 3-phenyl-6-methyl (III) and 3,6-diphenyl (IV) derivatives the 1,6-C=N double bond can be reduced in two one-electron steps. The reduction of the unprotonated form of these compounds occurs at potentials by 0.15V to 0.30V more negative in a pH-independent wave corresponding to a one-electron transfer to the 1,6-C=N bond. The reduction of the protonated form of 2,3-N=C bond occurs in all studied compounds in a single two-electron step. The reduction of the 1,6-C=N bond in compounds I, II and IV is considerably affected by covalent hydration. Dehydration of the resulting species is acid catalyzed. The negligible effect of replacement of the 3-methyl group in I by the 3-phenyl group in IV on the reduction potential confirms our earlier [3,10] observation that the delocalization of electrons in the grouping C=N-N=C is minimized. This conclusion is further supported by spectrophotometric and crystallographic data.

PL

We wszystkich badanych 4-amino-l,2,4-triazyno-5-on wiązanie 1,6-C=N jest elekrochemicznie redukowane przy potencjałach o ok. 0,5 V bardziej dodatnich niż wiązanie 2,3-N=C. Redukcja protonowanej formy wiązania 1,6-C=N zachodzi w pochodnych: 3-metylo-6-fenylo (I), 3-metylomerkapto-6-tert-butylo( II) i 3-metylo-6-tert-butylo (V), w pojedynczym 2-elektronowym etapie, podczas gdy wiązanie to w pochodnych: 3-metylo-6-fetylo (l) i 3,6-difenylo (IV) może być zredukowane w dwóch 1-elektronowych etapach. Redukcja nieuprotonowanej formy tych związków przebiega przy potencjałach od 0,15 do 0,30 V bardziej ujemnych i prowadzi do utworzenia fali l-elektronowej, niezależnej od pH. Redukcja uprotonowanej formy wiązania 2,3-N=C zachodzi we wszystkich związkach w pojedynczym 2-elektronowym etapie. Redukcja wiązania 1 ,6-C=N w związkach I, II i IV jest znacznie zmieniona przez kowalencyjne uwodnienie. Odwodnienie odpowiednich form badanych związków jest katalizowane kwasami. Stwierdzono nieistotny wpływ zastąpienia grupy 3-metylo przez grupę. 3-fenylo ( w związkach I, i IV) na potencjał redukcji, co potwierdza nasze wcześniejsze obserwacje [3,10], że delokalizacja elektronów w ugrupowaniu C=N-N=C jest zminimalizowana. Ten wniosek jest dodatkowo potwierdzony przez spekrro-fotometryczne i krystalograficzne dane.

7

Influence of Chemisorption o Sulfite Ions on Electroreduction of Gold(I)-Sulfite Complexes

Baltrunas G., Valiuniene A., Valiunas R.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 12

1819-1831

EN

Analysis of voltammograms, chronoamperograms and electrochemical impedance spectra (0.05÷4000 Hz) indicate a slow stage of chemisorption of sulfite ions that reduces an active surface of gold electrode, and significantly influences a parallel stage of charge transfer of gold(I)-sulfite complexes. The proposed equivalent circuit representing electrochemical process well fits to experimental dependencies of real and imaginary parts of impedance on frequency. Values of elements of equivalent circuit at different potentials of gold electrode (0.1÷-0.5 V) were calculated. Cathodic voltammogram simulated by using the dependencies of elements of equivalent circuit on electrode potential rather well represents experimentally obtained voltammograms.

8

Electroreduction of Dioxygen Catalyzed by Ferric Carboxymethylene-Cyclam Complex

Szulbiński W.

Polish Journal of Chemistry

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2000

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Vol. 74, nr 8

1163-1175

EN

On the basis of the electrochemical and spectroscopic data, mechanistic studies on the subject complex reactivity towards O2 are reported.

9

Electrochemical reduction of 1-Aryl-4-nitroazoles

Tallec A., Hazard R., Suwiński J., Wagner P.

Polish Journal of Chemistry

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2000

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Vol. 74, nr 8

1177-1183

EN

Electrochemical reduction of the nitro group in 1-aryl-4-nitroazoles occurs in slightly acidic medium as a typical four-electron process leading to hydroxylamine group formation. The forming 1-aryl-4-hydroxylaminoazoles undergo further reactions. Some products of this transformations, following the electrochemical reduction, were isolated and their structure were fully characterized by standard methods.

10

Electrochemical reduction of p-chloronitrobenzene in dipolar aprotic solvents containing carboxylic acids

Wagner-Czauderna E., Orłowska E., Kalinowski M.K.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 9

2127-2133

EN

The effect of carboxylic acids of different strenght on polarographic behaviour of p-chloronitrobenzene in N, N-dimethylformamide has been investigated. In the presence of each acid a pre-wave appeared at a more positive potential than the original one, which was associated with the cathodic reduction of a hydrogen-bonded adduct, formed between the nitrocompound and the acid molecules in the double layer of the electrode. A linear correlation has been found between delta E-1/2 and pK(DMF/HA) (pK(DMF/HA) refers to the value of the pK-a measured in N, N-dimethylformamide, whereas delta E-1/2=E(pre-wave/1/2) - E(original wave/1/2)). Measurements in a solvent series in the presence of benzoic acid (BA) led to the correlation between delta E-1/2 and pK-BA (the symbol pK-BA denotes the value measured in a given solvent). The slopes of regression lines are discussed in terms of the double layer effect on the basicity of the -NO2 group.

11

Electrochemical reactions of 1,8-anthraquinonedisulphonate potassium salt

Socha A.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 4

766-776

EN

Electrochemical reduction of 1,8-anthraquinonedisulphonate potassium salt forms anion radicals (EPR) and anthraquinone after oxidation of reduction products. Linear dependence of E(1/2) of equinone moiety reduction on LUMO energy was used for estimation of reduction potential of probable reaction products. Reduction of quinone moiety is quasireversible and two electrons are exchanged. Desulphonation proceeds in consecutive electrode steps of reduction.