1,4-Naphthoquinone Explained

1,4-Naphthoquinone or para-naphthoquinone is a quinone derived from naphthalene. It forms volatile yellow triclinic crystals and has a sharp odor similar to benzoquinone. It is almost insoluble in cold water, slightly soluble in petroleum ether, and more soluble in polar organic solvents. In alkaline solutions it produces a reddish-brown color. Vitamin K is a derivative of 1,4-naphthoquinone. It is a planar molecule with one aromatic ring fused to a quinone subunit.^[1] It is an isomer of 1,2-naphthoquinone.

Preparation

The industrial synthesis involves aerobic oxidation of naphthalene over a vanadium oxide catalyst:

CH + 3/2 O → CHO + HOIn the laboratory, naphthoquinone can be produced by the oxidation of a variety of naphthalene compounds. An inexpensive route involves oxidation of naphthalene with chromium trioxide.

Reactions

1,4-Naphthoquinone acts as strong dienophile in Diels-Alder reaction. Its adduct with 1,3-butadiene can be prepared by two methods: 1) long (45 days) exposure of naphthoquinone in neat liquid butadiene taken in huge excess at room temperature in a thick-wall glass tube or 2) fast catalyzed cycloaddition at low temperature in the presence of 1 equivalent of tin(IV) chloride:^[2]

Uses

1,4-Naphthoquinone is mainly used as a precursor to anthraquinone by reaction with butadiene followed by oxidation. Nitration gives 5-nitro-1,4-naphthalenedione, precursor to an that is used as a dye precursor.

Derivatives

Naphthoquinone forms the central chemical structure of many natural compounds, most notably the K vitamins. 2-Methyl-1,4-naphthoquinone, called menadione, is a more effective coagulant than vitamin K.

Other natural naphthoquinones include juglone, plumbagin, droserone.

Naphthoquinone derivatives have significant pharmacological properties. They are cytotoxic, they have significant antibacterial, antifungal, antiviral, insecticidal, anti-inflammatory, and antipyretic properties. Plants with naphthoquinone content are widely used in China and the countries of South America, where they are used to treat malignant and parasitic diseases.^[3]

Naphthoquinone functions as a ligand through its electrophilic carbon-carbon double bonds.^[4]

Notes and References

1. Gaultier, J. . Hauw, C. . Structure de l'α-Naphtoquinone . Acta Crystallographica . 1965 . 18 . 2 . 179–183 . 10.1107/S0365110X65000439 . 1965AcCry..18..179G .
2. M.A. Filatov . S. Baluschev . I.Z. Ilieva. V. Enkelmann . T. Miteva. K. Landfester . S.E. Aleshchenkov . A.V. Cheprakov . Tetraaryltetraanthra[2,3]porphyrins: Synthesis, Structure, and Optical Properties . J. Org. Chem. . 2012 . 77 . 24 . 11119–11131 . 10.1021/jo302135q . 23205621 .
3. Babula . P. . Adam . V. . Havel . L. . Kizek . R. . Naphthoquinones and their Pharmacological Properties . Czech . Ceská a Slovenská Farmacie . 2007 . 56 . 3 . 114–120 . 17867522 .
4. Kündig, E. P. . Lomberget, T. . Bragg, R. . Poulard, C. . Bernardinelli, G. . Desymmetrization of a meso-Diol Complex Derived from [Cr(CO){{sub|3}}(η{{sup|6}}-5,8-Naphthoquinone)]: Use of New Diamine Acylation Catalysts | journal = Chemical Communications | year = 2004 | volume = 2004 | issue = 13 | pages = 1548–1549 | doi = 10.1039/b404006f |pmid=15216374 }}

   Dichlone, a chlorinated derivative of 1,4-naphthoquinone, is used as a fungicide.

   See also

   • Hydroxynaphthoquinone
   • 1,4-Benzoquinone
   • Plumbagin
   • Hooker reaction

   References

   .