A hydroxynaphthoquinone is any of several organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

s with formula , which can be viewed as derivatives of a naphthoquinone

Naphthoquinone

Naphthoquinone is a class of natural phenols based on the C6-C4 skeleton.1,4-Naphthoquinone can be viewed as derivatives of naphthalene through the replacement of two hydrogen atoms by two ketone groups....

 through replacement of one hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 atom (H) by an hydroxyl

Hydroxyl

A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...

 group (-OH).

More generally, the term may mean any naphthoquinone derivative where any number n of hydrogens have been replaced by n hydroxyls, so that the formula is . In this case the number n (which is between 1 and 6) is indicated by a multiplier prefix

Prefix

A prefix is an affix which is placed before the root of a word. Particularly in the study of languages,a prefix is also called a preformative, because it alters the form of the words to which it is affixed.Examples of prefixes:...

 (mono-, di-, tri-, tetra-, penta-, or hexa-).

The unqualified term "hydroxynaphthoquinone" usually means a derivative of 1,4-naphthoquinone. Other hydroxy- compounds can be derived from other isomers of the latter, such as 1,2-naphthoquinone

1,2-Naphthoquinone

1,2-Naphthoquinone or ortho-naphthoquinone is a polycyclic aromatic organic compound with formula .This double ketone is a reactive metabolite of naphthalene and is found in diesel exhaust particles...

 and 2,6-naphthoquinone. The IUPAC nomenclature uses dihydronaphthalenedione instead of "naphthoquinone", with the necessary prefixes to indicate the positions of the carbonyl oxygens (=O) — as in 5,8-dihydroxy-1a,8a-dihydronaphthalene-1,4-dione (= 5,8-dihydroxy-1,4-naphthoquinone).

The hydroxynaphtoquinones (in the particular or the general sense) include many biologically and industrially important compounds, and are a building block of many medicinal drugs.

From 1,4-naphthoquinone

Due to the symmetry of the latter, there are only three isomers:

• 2-Hydroxy-1,4-naphthoquinone (lawsone), coloring principle of henna
  Henna
  Henna is a flowering plant used since antiquity to dye skin, hair, fingernails, leather and wool. The name is also used for dye preparations derived from the plant, and for the art of temporary tattooing based on those dyes...
  
  .
• 5-Hydroxy-1,4-naphthoquinone (juglone), coloring principle of black walnut
  Black Walnut
  Juglans nigra, the Eastern Black walnut, is a species of flowering tree in the hickory family, Juglandaceae, that is native to eastern North America. It grows mostly in riparian zones, from southern Ontario, west to southeast South Dakota, south to Georgia, northern Florida and southwest to central...
  
  . Also active antimicrobial principle in Caesalpinia sappan heartwood.
• 6-Hydroxy-1,4-naphthoquinone, can be prepared from 1,7-dihydroxynaphthalene. One of the main products of photochemical oxidation of 1-naphthol
  1-Naphthol
  1-Naphthol, or α-naphthol, is a colorless crystalline solid with the formula C10H7OH. It is an isomer of 2-naphthol differing by the location of the hydroxyl group on naphthalene. The naphthols are naphthalene homologues of phenol, with the hydroxyl group being more reactive than in the phenols....
  
  .

From 1,2-naphthoquinone

From 1,2-naphthoquinone

1,2-Naphthoquinone

1,2-Naphthoquinone or ortho-naphthoquinone is a polycyclic aromatic organic compound with formula .This double ketone is a reactive metabolite of naphthalene and is found in diesel exhaust particles...

 (ortho-naphthoquinone) there are 6 possible isomers:

• 3-Hydroxy-1,2-naphthoquinone
• 4-Hydroxy-1,2-naphthoquinone
• 5-Hydroxy-1,2-naphthoquinone
• 6-Hydroxy-1,2-naphthoquinone
• 7-Hydroxy-1,2-naphthoquinone
• 8-Hydroxy-1,2-naphthoquinone

From 2,3-naphthoquinone

From 2,3-naphthoquinone, also a symmetric molecule there are only three isomers:

• 1-Hydroxy-2,3-naphthoquinone
• 5-Hydroxy-1,2-naphthoquinone
• 6-Hydroxy-1,2-naphthoquinone

From 2,6-naphthoquinone

From the symmetrical 2,6-naphthoquinone (amphi-naphthoquinone) there are only three:

• 1-Hydroxy-2,6-naphthoquinone
• 3-Hydroxy-2,6-naphthoquinone
• 4-Hydroxy-2,6-naphthoquinone

(Poly)hydroxynaphthoquinones

• Dihydroxynaphthoquinone
  Dihydroxynaphthoquinone
  A dihydroxynaphthoquinone is any of several organic compounds with formula , which can be viewed as derivatives of naphthoquinone through replacement of two hydrogen atoms by hydroxyl groups ....
  
  
• Trihydroxynaphthoquinone
• Tetrahydroxynaphthoquinone
• Pentahydroxynaphthoquinone
• Hexahydroxynaphthoquinone
  Hexahydroxynaphthoquinone
  Hexahydroxynaphthoquinone can be any of several organic compounds, including:*Hexahydroxy-1,4-naphthalenedione *Hexahydroxy-1,2-naphthalenedione*Hexahydroxy-2,3-naphthalenedione*Hexahydroxy-2,6-naphthalenedione...