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Cyclic voltammetry of a unique quinone–quinol equilibrium
Author(s) -
Maali Nagwa Abo El,
Berg Hermann
Publication year - 1996
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.1140080819
Subject(s) - polarography , chemistry , quinone , cyclic voltammetry , analytical chemistry (journal) , electrochemistry , stereochemistry , electrode , organic chemistry
The thermochromic quinone‐quinol equilibrium of more than 20 derivatives was studied by classical DC‐polarography. This tautomery causes one reversible two‐electron wave and one irreversible (about 1 V) more negative wave. This double‐wave current‐voltage curve occurs only in the case of one asymmetric oxyethylamino substitution in the 2‐position for benzoquinones and for naphthoquinones. Our present investigations characterize further this unique slow equilibrium by the influence of the scan rate ν on cyclic voltammograms. The peak potentials are shifted to more negative values with increasing ν. Both the heights of the second wave and of the positive anodic step increase linearly with ν, whereas the height of the positive kinetic reduction wave behaves similarly only when ν < 25mVs −1 . However, at ν > 50mVs −1 the decyclization rate of quinol to quinone has no further influence on the first peak height and k 2 was determined directly and independently of former DC‐polarographic and spectrometric results.