POLYHYDROXY BENZENES

Polyhydric phenols with more than two hydroxy groups (ie, the three positional isomers of benzenetriol, the three isomeric benzenetetrols, benzenepentol [4270-96-6] and benzenehexol [608-80-0]) are discussed in this article. The benzenediols are catechol, resorcinol, and hydroquinone (see Hydroquinone, RESORCINOL, AND CATECHOL). 

The following names of the benzenetriols have been used. 

The benzenetetrols, -pentol, and -hexol do not have trivial names, except for 1,2,3,4-benzenetetrol [642-96-6] which was named apionol in some of the older hterature. The other two benzenetetrol isomers are 1,2,3,5- [634-94-6] and 1,2,4,5-benzenetetrol [636-32-8]. 

Identification, isolation, and removal of (polyhydroxy)benzenes from the environment have received increased attention throughout the 1980s and 1990s. The biochemical activity of the benzenepolyols is at least in part based on thek oxidation—reduction potential. Many biochemical studies of these compounds have been made, eg, of enzymic glycoside formation, enzymic hydroxylation and oxidation, biological interactions with biochemically important compounds such as the catecholamines, and humic acid formation. The range of biochemical function of these compounds and thek derivatives is not yet fully understood. 

PyrogaHol (1) was first observed by Scheele in 1786 as a product of the dry distillation of gaUic acid [149-91-7] (3,4,5-ttihydroxybenzoic acid). PyrogaHol, which is of widespread occurrence in nature, is incorporated in tannins, anthocyanins, flavones, and alkaloids (1). 

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