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 SM ISO690:2012KIRIYAK, Ludmila, CIOCOI, N, REVENKO, M.. Chlorate catalytic waves in the presence of molybdenum(VI) complex with 2,3-dihidroxybenzaldehyde. In: Physical Methods in Coordination and Supramolecular Chemistry, 27 septembrie - 1 octombrie 2006, Chişinău. Chisinau, Republic of Moldova: 2006, XVII, p. 141. ISBN 978-9975-62-066-6. |
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| Physical Methods in Coordination and Supramolecular Chemistry XVII, 2006 |
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Conferința "The XV-th International Conference Physical Methods in Coordination and Supramolecular Chemistry : The XVII-th Reading in memory of Acad. A.Ablov" Chişinău, Moldova, 27 septembrie - 1 octombrie 2006 | ||||||
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It has been shown earlier that the presence of hidroxyacids or pyrocatechin increases the catalytic activity of the molybdenum if chlorate ion is used as oxidant. The results of the investigation of the effects caused by the presence of 2,3-dihydroxybenzaldehyde (DHBA) will be discussed in this presentation. The presence of the DHBA in the system Мо(VI) - KClO3 gives rise to the appearance on the direct current polarograms, recorded with a dropping mercury electrode, of an intensive wave with a well defined maximum. To establish the nature of this wave a detailed investigation has been undertaken. The optimal pH range, where the analytical signal has a maximal intensity is in the range 2,0-2,3. Variation of the mercury column height (h), temperature(t), and concentration of the reagents (Мо(VI), DНВА, and KClO3) on the current values, suggest an electrocatalytic character of this reaction. The unusual form of the wave should be caused by the adsorption of the reagents on the mercury electrode, as well as by the high rate of the chemical reaction occurring at the mercurysolution interface. The rate of this reaction is responsible for the electrocatalytic process on the whole. The analysis of the experimental data suggests that the electrochemical signals recorded in this system could be governed by the reactions described by the schemes: Мо(VI) + DНВА ↔ [Мо(VI)(DНВА)] + Н+ (1) [Мо(VI)(НВА)] + e → [Мо(V) (DНВА)] (2) [Мо(V)(DНВА)] + ClO3 - ↔ [Мо(V)(DНВА(ClO3 -)] (3) [Мо(V)(DНВА(ClO3 -)] ⎯⎯⎯→ 2H + [Мо(VI) (DНВА] +ClO2 + H2O (4) The limiting step of the process, which one determines the current value, is the reaction (3). The regeneration of the catalyst [Мо(VI)(DНВА] is the result of an inner sphere electron transfer from Mo(V) to ClO3 - (reaction 4). The current is proportional to the concentration of the molybdenum in the range 5⋅10-8 - 1⋅10-6 mol/l and may be used for determination of this metal at the trace level (up to 5 ppb), being a very sensitive electrochemical method using the direct current polarography. The interferences of a number of cationic and anionic species have been investigated. |
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