First Direct Detection of Chromium(IV) as a Long Lived Intermediate in the Oxidation of Methanol by Chromium(VI)

Reduction of chromium(VI) by excess methanol in solutions buffered by 2-ethyl-2-hydroxy butanoic acid and its sodium salt proceeds through a 2-electron path to produce pink chromium(IV). With the progress of this reaction, a slow oxidation of the product chromium(IV) by reactant chromium(VI) takes place. When all the chromium(VI) is consumed, the chromium(IV) undergoes very slow disproportionation to chromium(V) and chromium(III). The formation of chromium(IV) is accelerated by both 2-ethyl-2-hydroxy butanoate ion and hydrogen ion.