In 1826, the French chemist
Pierre Jean Robiquet had isolated from the root of a plant,
madder, and defined the structure of, alizarin, a remarkable red dye. Liebermann's 1868 discovery that alizarin can be reduced to form
anthracene, which is an abundant component in coal tar, opened the road for synthetic alizarin. The patent of Liebermann and
Carl Gräbe for the synthesis of alizarin from anthracene was filed one day before the patent of
William Henry Perkin. The synthesis is a chlorination or bromination of anthracene with a subsequent oxidation forming the alizarin. ==See also==