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Pulse polarography of azobenzene
Author(s) -
KomorskyLovrić ŠEbojka,
Lovrić Milivoj
Publication year - 1994
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.1140060807
Subject(s) - azobenzene , chemistry , polarography , acetonitrile , aqueous solution , adsorption , inorganic chemistry , solvent , photochemistry , organic chemistry , molecule
Pulse polarography is applied to measure adsorption of azobenzene and hydrazobenzene in a wide acidity range between 5 M HClO 4 and 0.5 M NaClO 4 buffered to pH 7. The solvent is 20% v/v aqueous acetonitrile. In 5 M HClO 4 the adsorption of azobenzene is weaker, while at pH 7 it is stronger than the adsorption of hydrazobenzene. In weakly acidic and neutral NaClO 4 solutions, the surface protonization of azobenzene is a rate‐determining step of the redox reaction. When the polarographic pulse is very short, the unprotonated azobenzene is reduced directly and at potentials which are more negative than the potentials at which the monoprotonated azobenzene is reduced if pulses are longer. The rate constants of benzidine rearrangement of adsorbed hydrazobenzene are measured in concentrated HClO 4 solutions: k = 52 s −1 , 115 s −1 , and 224 s −1 for 1, 3, and 5 M HClO 4 , respectively.