Dihydroxy Benzenoid Compounds

The reactions reviewed in this group consist of oxidation and substitution in the ring for the benzenoid series and a number of sequences involving polycyclic compounds which contain 1,4-dihydroxy systems. 

Hydroquinone in isopropanol containing a small proportion of iodine by gradual addition of 35% hydrogen peroxide over 3 hours and subsequent reaction for the same period, furnished an 86% yield of 1,4-benzoquinone (ref.156). 

A quantitative yield of 2,3,6-trimethylbenzo-1,4-quinone was obtained from 

6-trimethylhydroquinone and phenyl iodosodiacetate (1 mole) in methanol at ambient temperature. The reagent also has applicability to 4-alkylphenols and 

Reactions involving substitution in the ring are of two types, those consisting of attachment of a group to the ring and those where an alkoxyl group is formed and ring closure leads to a polycyclic compound. 

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