Hydroxynaphthoquinone Explained

A hydroxynaphthoquinone (formula:) 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In general, the term may mean any naphthoquinone derivative where any number n of hydrogens have been replaced by n hydroxyls, so that the formula is . 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.^{[1] [2] [3]}

(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.^[4] Also active antimicrobial principle in Caesalpinia sappan heartwood.^[5]
• 6-Hydroxy-1,4-naphthoquinone, can be prepared from 1,7-dihydroxynaphthalene.^[6] One of the main products of photochemical oxidation of 1-naphthol.^[7]

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^{[8] [9]}
• 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

See also

• Hydroxybenzoquinone
• Hydroxyanthraquinone

Notes and References

1. Khalafy, J. . Bruce, J. M. . 2002 . Oxidative Dehydrogenation of 1-Tetralones: Synthesis of Juglone, Naphthazarin, and α-Hydroxyanthraquinones . Journal of Sciences, Islamic Republic of Iran . 13 . 2 . 131–139 . pdf .
2. Book: Thomson, R. H. . Naturally Occurring Quinones . registration . Academic Press . London . 1971 . Quoted by Khalafy and Bruce.
3. Book: Thomson, R. H. . Naturally Occurring Quinones III . Chapman and Hall . London . 1987 . Quoted by Khalafy and Bruce.
4. Taylor, R. T. . Flood, L. A. . Polystyrene-Bound Phenylseleninic Acid: Catalytic Oxidations of Olefins, Ketones, and Aromatic Systems . The Journal of Organic Chemistry . 1983 . 48 . 26 . 5160–5164 . 10.1021/jo00174a003 .
5. Lim, M.-Y. . Jeon, J.-H. . Jeong, E. Y. . Lee, C. H. . Lee, H.-S. . Antimicrobial Activity of 5-Hydroxy-1,4-Naphthoquinone Isolated from Caesalpinia sappan toward Intestinal Bacteria . Food Chemistry . 2007 . 100 . 3 . 1254–1258 . 10.1016/j.foodchem.2005.12.009 .
6. Teuber, H.-J. . Götz, N. . Reaktionen mit Nitrosodisulfonat, V. Mitteilung: Über die Bildung von Naphtochinonen . Chemische Berichte . 1954 . 87 . 9 . 1236–1251 . 10.1002/cber.19540870908 .
7. Brahmia, O. . Richard, C. . Photochemical Transformation of 1-Naphthol in Aerated Aqueous Solution . Photochemical & Photobiological Sciences . 2005 . 4 . 6 . 454–458 . 10.1039/B504309C . 15920628 . free .
8. Garge, P. . Padhye, S. . Tuchagues, J.-P. . Iron(II) Complexes of ortho-Functionalized para-Naphthoquinones 1. Synthesis, Characterization, Electronic Structure and Magnetic Properties . Inorganica Chimica Acta . 1989 . 157 . 2 . 239–249 . 10.1016/S0020-1693(00)80548-4 .
9. Rane, S. Y. . Ahmed, K. . Salunke-Gawali, S. . Temperature Effect on Ancillary μ-Carbonato Ligand Modes in Hydroxy Naphthoquinonato Copper(II) Complex: An EPR Spectroscopic and Magnetic Coupling Evidences . Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry . 2006 . 36 . 5 . 391–398 . 10.1080/15533170600729037 .