5,8-Dihydroxy-1,4-naphthoquinone

Chemical properties

dark purple to brown-black powder

Definition

ChEBI: A naphthoquinone that is 1,4-naphthoquinone in which the hydrogens at positions 5 and 8 are replaced by hydroxy groups.

Preparation

1,8-Dinitronaphthalene and 1,5-Dinitronaphthalene mixture or both alone and one of sulfur 40% fuming sulfuric ACID reaction, the product (5, 8 – dihydroxy – naphthoquinone) into Sulfurous acid?hydrogen salt.

Purification Methods

It crystallises in red-brown needles with a green shine from EtOH. It also crystallises from hexane and is further purified by sublimation at 2-10mm. [Huppert et al. J Phys Chem 89 5811 1985.] It is sparingly soluble in H2O but soluble in alkalis. The diacetate forms golden yellow prisms from CHCl3, m 192-193o and the 5,8-dimethoxy derivative has m 157o (155o) (from pet ether) [Bruce & Thompson J Chem Soc 1089 1955, IR: Schmand & Boldt J Am Chem Soc 97 447 1975, NMR: Brockmann & Zeeck Chem Ber 101 4221 1968]. The monothiosemicarbazone has m 168o(dec) from EtOH [Gardner et al. J Am Chem Soc 74 2106 1952]. [Beilstein 8 H 412, 8 III 3600.]

Properties and Applications

ash red to black. Soluble in water for red light brown, soluble in ethanol for yellow brown, with green fluorescence. In concentrated sulfuric acid to dark yellow green, heating to rouge red, dilution after brown black precipitation. Dye aqueous solution to join sodium hydroxide to red, the air oxidation into blue.