Like all the groups reviewed until now does this one also consist of a large number of molecules of heterogeneous structure. Their common feature is the presence of at least one hydroxyl-substituted aromatic ring system.
Most phenolic compounds belong to the flavonoids .
Lignin , the primary substance of wood, is most frequent. The following table outlines the most important classes. The starting product of the biosynthesis of most phenolic compounds is shikimate . Phenols are acidic due to the dissociability of their -OH group. They are rather reactive compounds and as long as no steric inhibition due to additional side chains occurs do they form hydrogen bonds.