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Kinetic study of the fast step of the alkaline hydrolysis of p ‐chloranil using stopped flow technique
Author(s) -
Lafis S.,
Konidari C. N.,
Veltsistas P. G.,
Tzerpos N.,
Karayannis M. I.
Publication year - 1997
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(1997)29:5<385::aid-kin9>3.0.co;2-q
Subject(s) - chloranil , chemistry , hydrolysis , reaction rate constant , alkaline hydrolysis , photochemistry , kinetics , ion , analytical chemistry (journal) , chromatography , organic chemistry , physics , quantum mechanics
The alkaline hydrolysis of p ‐chloranil or 2,3,5,6‐tetrachloro‐1,4‐benzoquinone (C 6 Cl 4 O 2 , Q) 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. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 385–391, 1997