Autocatalysis-driven clock reaction II: Kinetics of the pentathionate-periodate reaction

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Abstract

The pentathionate-periodate reaction has been investigated by spectrophotometrically monitoring the total amount of iodine evolved in the presence of phosphoric acid/dihydrogen phosphate buffer at 468 nm. The majority of the main characteristics of the title system is very reminiscent of that found recently in the pentathionate-iodate reaction, a system that led us to classify generally the clock reactions. Along with the pentathionate-iodate reaction the title system is proposed to belong to the autocatalysis-driven clock reactions as well. The kinetic model of the pentathionate-iodate system published recently was implemented by the necessary reactions of periodate to compose a 24-step kinetic model in which the mechanisms of the pentathionate-iodine, pentathionate-iodate, bisulfite-periodate, bisulfite-iodate, iodide-periodate, and the well-known Dushman reactions are combined. A thorough analysis revealed that the direct pentathionate-periodate reaction plays a role only to produce iodide ion via a finite sequence of reactions, and once its concentration reaches a certain level, the reaction is almost exclusively governed by the pentathionate-iodine, the iodide-periodate, and the Dushman reactions. As expected strong catalytic effect of the buffer composition is also found that can readily be explained by its well-known catalytic influence on the Dushman reaction.

Original languageEnglish
Pages (from-to)9811-9819
Number of pages9
JournalJournal of Physical Chemistry A
Volume118
Issue number42
DOIs
Publication statusPublished - Oct 23 2014

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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