title: Hydroxynaphthoquinone
text: # Hydroxynaphthoquinone
  
  A hydroxynaphthoquinone (formula: C $_{10}H$ $_6O$ $_3)$ is any of several organic compounds that can be viewed as derivatives of a naphthoquinone through replacement of one hydrogen atom (H) by a hydroxyl group (-OH).
  
  In general, the term may mean any naphthoquinone derivative where any number n of hydrogens have been replaced by n hydroxyls, so that the formula is C $_{10}H$ $_6O$ $_{2+n}.$ In this case the number n (which is between 1 and 6) is indicated by a multiplier prefix (mono-,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 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.
  
  ## (Mono)hydroxynaphtoquinones
  
  ### From 1,4-naphthoquinone
  
  Due to its symmetry there are only three isomers:
  
  * 2-Hydroxy-1,4-naphthoquinone (lawsone), coloring principle of henna.
  * 5-Hydroxy-1,4-naphthoquinone (juglone), coloring principle of black walnut. 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.
  
  ### From 1,2-naphthoquinone
  
  From 1,2-naphthoquinone (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
  * Trihydroxynaphthoquinone
  * Tetrahydroxynaphthoquinone
  * Pentahydroxynaphthoquinone
  * Hexahydroxynaphthoquinone
  