1,4-Naphthoquinone

Naphthoquinone[1]
Names
	Preferred IUPAC name Naphthalene-1,4-dione
	Other names 1,4-Naphthoquinone; Naphthoquinone; α-Naphthoquinone
Identifiers
CAS Number	130-15-4 ;
3D model (JSmol)	Interactive image;
ChEMBL	ChEMBL55934 ;
ChemSpider	8215;
ECHA InfoCard	100.004.526
PubChem CID	8530;
UNII	RBF5ZU7R7K ;
CompTox Dashboard (EPA)	DTXSID5040704 ;
	InChI InChI=1S/C10H6O2/c11-9-5-6-10(12)8-4-2-1-3-7(8)9/h1-6H Key: FRASJONUBLZVQX-UHFFFAOYSA-N; InChI=1/C10H6O2/c11-9-5-6-10(12)8-4-2-1-3-7(8)9/h1-6H Key: FRASJONUBLZVQX-UHFFFAOYAK;
	SMILES O=C2C=CC(C1=CC=CC=C12)=O;
Properties
Chemical formula	C10H6O2
Molar mass	158.15 g/mol
Density	1.422 g/cm3
Melting point	126 °C (259 °F; 399 K)
Boiling point	Begins to sublime at 100 °C
Solubility in water	0.09 g/L
Magnetic susceptibility (χ)	-73.5·10−6 cm3/mol
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

1,4-Naphthoquinone or para-naphthoquinone is an organic compound 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.[2] It is an isomer of 1,2-naphthoquinone.

Preparation

The industrial synthesis involves aerobic oxidation of naphthalene over a vanadium oxide catalyst:[3]

C₁₀H₈ + 3/2 O₂ → C₁₀H₆O₂ + H₂O

In 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.[4]

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:[5]

Diels-Alder reaction of 1,4-naphthoquinone with 1,3-butadiene

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 aminoanthroquinone that is used as a dye precursor.[3]

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 naphtoquinones 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.[6]

Naphthoquinone functions as a ligand through its electrophilic carbon-carbon double bonds.[7]

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

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