Oxidation of Phenol

Phenol is oxidised by air, or by acidified K2Cr2O7 in concentrated H2SO4, to 1,4-benzoquinone -- the -OH-bearing ring carbon and the para carbon both become carbonyl (=O) carbons, breaking the ring's full aromaticity. This ready oxidisability is also WHY phenol slowly turns pink on standing in air and light (section 11.14) -- trace amounts of coloured, partially-oxidised quinonoid imp …