Nucleophilic addition of thiaproline to electrochemically derived o-quinone, application to the sensitive voltammetric detection of thiaproline

Shahrokhian, S ; Sharif University of Technology | 2006

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  1. Type of Document: Article
  2. DOI: 10.1002/elan.200603616
  3. Publisher: 2006
  4. Abstract:
  5. The mechanism of electrochemical behavior of catechol in the presence of thiaproline is investigated by cyclic voltammetry, controlled-potential coulometry and spectrophotometric tracing of the reaction coordinate. The results indicate that thiaproline participate in with an ECEC mechanism in a nucleophilic (Michael) addition to o-quinone. Effect of pH of buffer solution on reaction pathway is studied and showed that addition of thiaproline to the o-quinone is performed only in solutions with pHs higher than 5. These results indicate that the addition of thiaproline is occurred first from amine functional group. In the second step, the addition of carboxylate group of thiaproline to C-5 of catechol results the final product with a lactone ring in its structure. Observation of two isosbestic point in absorption spectrum during the progress of the electrolysis together with the FT-IR results for final product can be presented as evidence for two step addition of thiaproline to catechol. Final product, due to the electron donor property of thiaproline, more easily oxidized respect to the former catechol and as a result, a new redox couple is obtained for this compound in lower potentials. The easier anodic oxidation of addition product (relative to catechol) caused to an increase in anodic current for catechol, which is proportional to the thiaproline concentration. The differential pulse voltammetry (DPV) is applied as a sensitive voltammetric method for the detection of thiaproline. A linear range from 5 × 10-8 to 5 × 10-6 M with a detection limit of 1 × 10-8 M is resulted for thiaproline. With respect to the reversibility of the electrochemical reactions in the mechanism, and also more facile oxidation of the addition products, the square-wave voltammetry is presented as a method with considerably more sensitivity for the detection of sub-micromolar amounts of thiaproline. The advantageous properties of the voltammetric method for thiaproline detection lie in its excellent catalytic activity, sensitivity and simplicity. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA
  6. Keywords:
  7. Catechol ; Controlled-potential coulometry ; Cyclic voltammetry ; Differential pulse voltammetry ; Michael addition ; Square-wave voltammetry ; Thiaproline
  8. Source: Electroanalysis ; Volume 18, Issue 22 , 2006 , Pages 2225-2231 ; 10400397 (ISSN)
  9. URL: https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/elan.200603616