These molecules can be further oxidized to form a class of molecules called hydroxyquinones.
Hydroxyquinones share the same ring and carbonyl backbone as quinones, but differ by the
addition of one or more hydroxyl groups. Many hydroxyquinones have biological activity, and some
are used in the synthesis of medications. One classic example is shown in Figure 5.14.
Figure 5.14. 2-Hydroxy-1,4-benzoquinone, a HydroxyquinoneMCAT EXPERTISE
Note the subtle difference in terminology between Figure 5.12 and Figure 5.14.
A hydroquinone is a benzene ring with two hydroxyl groups. A hydroxyquinone contains two
carbonyls and a variable number of hydroxyl groups.Because of resonance, hydroxyquinones behave like quinones with electron-donating groups,
making these slightly less electrophilic (although still quite reactive). When naming these
compounds, the position of the hydroxyl groups is indicated by a number, and the total number of
hydroxyl groups (if there is more than one) is indicated by a prefix (such as di–, or tri–) with the
substituent name hydroxy–. Several examples are shown in Figure 5.15.
Figure 5.15. Three Examples of Hydroxyquinones
(a) Tetrahydroxybenzoquinone; (b) 5-hydroxynaphthoquinone; (c) 1,2-dihydroxyanthraquinone.