Electron transfer oxidations of organic compounds. Part IV. The kinetics of oxidations of some difunctional ketonic substrates by the hexachloroiridate(IV) anion, the oxidation of 2-chlorocyclohexanone by hexachloro- and hexabromo-iridate(IV), and a survey of the reactivity of hexachloroiridate(IV) towards organic compounds

Abstract

The reactions between hexachlororidiate(IV) in dilute mineral acid and the substrates 2-chloro- and 2-hydroxycyclohexanone have been studied kinetically in acid solution and found to be dependent on the rate of enolisation of the substrate. Hexabromoiridate(IV) behaved similarly with the former compound. The substrates 2-oxocyclohexanone and acetylacetone, which have a high enol content, are however not found to react exceptionally rapidly, since their enols are relatively inert and the reactions proceed mainly by oxidation of the enol anions. These reactions all appear to proceed by outer-sphere electron-transfer mechanisms. Oxalic acid, pyruvic acid, and mandelic acid are only attacked slowly by hexachloroiridate(IV), while cyclohexanol, 2,3-dimethylbutane-2,3-diol, and acetaldehyde do not react detectably. The last compounds, though normally readily oxidised by one-equivalent oxidants with which they can complex, are not susceptible to electron-transfer oxidation by hexachloroiridate(IV).