2.6- Dimethoxy-5,8-dihydroxy-naphthoquinone

Naphthazarin (5,8-dihydroxy-1,4-naphthoquinone) [475-38-7] M 190.2, m 220-230°(dec), m 225-230°, pKEst(i) 9.5, pKEst(2) ll-l Red-brown needles with a green shine from EtOH. Also recrystd from hexane and purified by vacuum sublimation. [Huppert et al. J Phys Chem 89 5811 1985.] It is sparingly soluble in H2O but soluble in alkalis. It sublimes at 2-10mm. The diacetate forms golden yellow prisms from CHCI3, m 192-193° and the 5,8-dimethoxy derivative has m 157° (155°) (from pet ether) [Bruce and Thompson J Chem Soc 1089 7955 IR Schmand and Boldt J Am Chem Soc 97 447 1975 NMR Brockmann and Zeeck Chem Ber 101 4221 1968]. The monothiosemicarbazone has m 168°(dec) from EtOH [Gardner et al. J Am Chem Soc 74 2106 7952]. 

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