Quinones are organic compounds that are formally derived from aromatic
compounds such as benzene or naphthalene. During the conversion, an even
number of (CH) groups are oxidised into (C=O) groups and necessary double
bonds are rearranged to get fully conjugated cyclic dione structure1. Apart from
this, organic molecules such as phenols and catechols having electron donating
substituents are easily oxidized to quinones. The electron donating substituents
increase the nucleophilicity of the ring and contributes to the large redox
potential needed to break the aromaticity (quinones are conjugated but not
aromatic).
Many natural and artificial colouring substances (dyes and pigments) are quinone
derivatives. They are next to azo dyes in importance as dyestuffs with particular
emphasis on blue colours. Alizarin {1,2-dihydroxy-9,10-anthraquinone} (8),
extracted from the madder plant, was the first natural dye to be synthesized from
anthracene. This was used as the prominent red dye for dyeing textile fabrics.
