2,3,5,6,8-Pentahydroxy-1,4-naphthalenedione, also called 2,3,5,6,8-pentahydroxy-1,4-naphthoquinone or spinochrome D, is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

with formula , formally derived from 1,4-naphthoquinone through the replacement of five

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

atoms by

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

(OH) groups. Spinochrome D occurs naturally as a brownish red

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...

in the

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard ou ...

and spines of sea urchins such as the Japanese ''aka-uni'' ('' Pseudocentrotus depressus''). Chika KURODA and Masae OKAJIMA (1967), ''Studies on the Derivatives of Naphthoquinones, XVIII. The pigments of sea urchins, XIII''. Proc. Japan Acad., volume 43, pages 41--44
Online version
accessed on 2010-02-01. It is soluble in

diethyl ether Diethyl ether, or simply ether, is an organic compound in the ether class with the formula , sometimes abbreviated as (see Pseudoelement symbols). It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable liq ...

and crystallizes as brownish red needles that sublime at 285−295 °C. The compound gives a yellowish brown solution when treated with

sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkali ...

, a bluish green solution with

ferric chloride Iron(III) chloride is the inorganic compound with the formula . Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The colo ...

, and a violet precipitate with

lead acetate Lead acetate can refer to: * Lead subacetate (Basic lead acetate), Pb3(OH)4(CH3COO)2 * Lead(IV) acetate (plumbic acetate), Pb(CH3COO)4 * Lead(II) acetate Lead(II) acetate (Pb(CH3COO)2), also known as lead acetate, lead diacetate, plumbous acetat ...

. It forms a five-fold

acetate An acetate is a salt (chemistry), salt formed by the combination of acetic acid with a base (e.g. Alkali metal, alkaline, Alkaline earth metal, earthy, Transition metal, metallic, nonmetallic or radical Radical (chemistry), base). "Acetate" als ...

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

, ()₅, that crystallizes from

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

as yellow needles that melt at 185−186 °C.

References

{{DEFAULTSORT:Pentahydroxy-1,4-naphthalenedione, 2,3,5,6,8- 1,4-Naphthoquinones Catechols Hydroxyquinols Polyols Hydroxynaphthoquinones

See also

References