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Kinetics and mechanism of electron transfer from phenolate anion to hexacyanoferrate (III) in aqueous alkaline media
Author(s) -
Panda Pradeepta K.,
Panda Rama Krushna,
Murti P. S. Radhakrishna
Publication year - 1987
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/kin.550190207
Subject(s) - chemistry , electron transfer , reaction rate constant , ionic strength , aqueous solution , kinetics , ion , ionic bonding , phenol , inorganic chemistry , redox , aqueous medium , reaction mechanism , photochemistry , organic chemistry , catalysis , physics , quantum mechanics
A kinetic reinvestigation of the title redox system in aqueous alkaline media at 35°C and an ionic strength of 0.5 mol dm −3 shows that the reaction follows a pseudosecond‐order Fe(CN) 6 3−disappearance. While varying [phenol] 0 and [OH − ] exhibit a linear influence on the pseudo‐second‐order rate constant, varying[Fe(CN) 6 3− ] 0 and [Fe(CN) 6 4− ] 0 , initially taken, have a complicated inhibitory effect on the same. The major phenoloxidation products isolated under a chosen condition are 2,2′‐ and 4,4′‐ dihydroxydiphenyl. Results are interpreted in terms of a probable mechanism which envisages a reversible formation, by the first one‐electron transfer, of a reactive phenoxy radical (PhO ˙ ) which on the second one‐electron transfer forms a less reactive ion‐pair intermediate (stabilized by the Fe(CN) 6 4−produced) to decompose rate‐determiningly to phenoxonium cation (PhO + ) and Fe(CN) 6 4− , the product‐formation steps being very rapid and kinetically indistinguishable.