Kinetic study of the fast step of the alkaline hydrolysis of p-chloranil using stopped flow technique (Journal article)

Lafis, S./ Konidari, C. N./ Veltsistas, P. G./ Tzerpos, N./ Karayannis, M. I.

The alkaline hydrolysis of p-chloranil or 2,3,5,6-tetrachloro-1,4-benzoquinone (C6Cl4O2, O) was studied, using stopped flow spectrophotometry and Electron Spin Resonance techniques (E.S.R.). In the present study it was shown for the first time, that a free radical is produced chemically and that it can account for the propagation of the reaction. It was found that in alkaline conditions chloranil in a ''Michael'' fashion undergoes 1,2 addition being hydrolyzed and in turn produces a chloranil free radical (Q.). The hydrolysis then proceeds via a number of intermediates yielded by this radical and a number of different products is formed. The formation of these products, both quantitatively and qualitatively has a strong dependence on the concentration of the OH- species and chloranil. The various possible routes of the hydrolysis are studied either spectrophotometrically or by E.S.R. Two different intermediates are observed absorbing at 426 nm and at 540 nm, respectively. Each species was formed and destroyed within 10 s to 30 min depending on the exact conditions. The reaction rate constants for the formation and the decay of the intermediates was estimated using the Guggenheim method. At both wavelengths the rate constants seem to have a complex relation to the concentration of the anion. (C) 1997 John Wiley & Sons, Inc.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
Keywords: proton-transfer,radical cation
ISSN: 0538-8066
Link: <Go to ISI>://A1997WU98500009<385::AID-KIN9>3.0.CO;2-Q/asset/9_ftp.pdf?v=1&t=h0dvzsno&s=83fb56a9d46437380f9d4c71d19b346044695114
Publisher: Wiley-Blackwell
Appears in Collections:Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

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