Reduction of hexachloroiridate (IV) by benzene‐1,2‐diol in aqueous perchloric acid

Abstract

The kinetics of the reaction between benzene-1,2-diol(catechol) and hexachloroiridate (IV) have been measured in aqueous acidic perchlorate solutions by the stopped-flow method. The reaction is second order overall, and first order in each reactant. A reverse reaction also occurs, but it is much slower than the forward process. Observed rate constants are dependent on acidity, but the variation can be attributed to activity rather than mechanistic effects. The reaction appears to proceed predominantly by an outer sphere electron transfer mechanism. yielding o-benzoquinone and hexachloroiridate (III), although rnonoaquopentachloroiridate (111) is formed also a t the higher (catechol]/[IrC~~-] ratios.

Kinetics of the reduction of tetrakis (2,2′-bipyridine)-μ-oxo-di-iron(III) by 1,3-benzenediol in aqueous acidic medium

“…by 1,2-, 1,3-and 1,4-benzenediols but different from the reduction of IrCl 6 2-by these reductants [36]. Therefore, outer-sphere mechanism, via ion-pair formation is proposed for this reaction.…”

Absorption Spectrum, Mass Spectrometric Properties, and Electronic Structure of 1,2-Benzoquinone

“…Tunneling between these states is clearly of considerable importance. We estimate the tunneling frequency to be ∼10 6 Hz by assuming a WKB approximation on a cosine-shaped potential.…”

“…Mason isolated ortho -quinone produced by the enzymatic oxidization of catechol and found that it has a broad absorption band at ∼390 nm with an extinction coefficient in the range of 1300−1800 M −1 cm −1 . A number of investigators have examined the kinetics of the oxidation of catechol by a variety of inorganic oxidants. – Of particular relevance to the present study is the report by Mentasi and co-workers that catechol is rapidly oxidized by hexachloroiridate(IV) to produce ortho -quinone. Morrison and Ritter studied the kinetics of the reduction of hexachloroiridate(IV) by catechol and found the reaction rate to be dependent on acidity.…”

“…A number of investigators have examined the kinetics of the oxidation of catechol by a variety of inorganic oxidants. – Of particular relevance to the present study is the report by Mentasi and co-workers that catechol is rapidly oxidized by hexachloroiridate(IV) to produce ortho -quinone. Morrison and Ritter studied the kinetics of the reduction of hexachloroiridate(IV) by catechol and found the reaction rate to be dependent on acidity. In a very important study, Nagakura and Kuboyama found that in benzene solution ortho -quinone exhibits a very strong dipole having a moment of 5.1 D.…”