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Overoxidation of phenol by hexachloroiridate(IV)
1Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA.
Inorganic Chemistry
|November 18, 2011
Summary
The aqueous oxidation of phenol by iridium hexachloride involves phenoxyl radical coupling and overoxidation. The extent of overoxidation is pH-dependent, influencing the overall reaction rate and mechanism.
Area of Science:
- * Inorganic Chemistry
- * Reaction Kinetics
Background:
- * Aqueous oxidation of phenol by hexachloroiridate(IV) ([IrCl6]2-) produces phenoxyl radicals.
- * Phenoxyl radical coupling yields biphenols and phenoxyphenols, which can undergo further oxidation (overoxidation).
Purpose of the Study:
- * To investigate the kinetics and mechanisms of overoxidation products of phenol.
- * To elucidate the pH-dependent behavior of the phenol oxidation reaction.
Main Methods:
- * Determination of rate constants for the oxidation of four coupling products by [IrCl6]2-.
- * Kinetic simulations of a combined reaction mechanism.
Main Results:
- * Rate laws for the oxidation of coupling products match the form for phenol oxidation.
- * Kinetic simulations reveal pH-dependent overoxidation, limited at high pH and extensive at low pH.
- * Overoxidation introduces minor deviations in the phenol oxidation rate law, explainable by pH-dependent effects.
Conclusions:
- * Overoxidation of phenol coupling products is a significant factor in the overall reaction.
- * The observed pH dependence of the reaction rate law originates from pH-dependent overoxidation.
- * Understanding these overoxidation pathways is crucial for accurately describing the phenol-iridium hexachloride reaction mechanism.
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