2-Hydroxy-1,4-naphoquinone Chemical Properties
- Melting point:
- 192-195 °C (dec.)(lit.)
- Boiling point:
- 265.11°C (rough estimate)
- 1.2346 (rough estimate)
- refractive index
- 1.5036 (estimate)
- Crystalline Powder
- Colour Index
- Water Solubility
- 2 g/L (20 ºC)
- Stable. Combustible. Incompatible with strong oxidizing agents.
- CAS DataBase Reference
- 83-72-7(CAS DataBase Reference)
- NIST Chemistry Reference
- 1,4-Naphthalenedione, 2-hydroxy-(83-72-7)
- EPA Substance Registry System
- 2-Hydroxy-1,4-naphthoquinone (83-72-7)
2-Hydroxy-1,4-naphoquinone Usage And Synthesis
2-Hydroxy-1,4-naphthoquinone (HNQ, C10H6O3) is also called Lawsone, which is a white cubic crystal. Its melting point is 192-195 oC, and flash point is 192 oC. The solubility of HNQ is 2 g/L in water at 20 oC. It is stable, but it is combustible and incompatible with strong oxidizing agents.
2-Hydroxy-1,4-naphthoquinone(HNQ) is the principal natural dye ingredient contained at 1.0-1.4% in the leaves of Henna (Lawsonia inermis). It is an ancient red-orange dye. Henna has been used for more than 4000 years not only as a hair dye, but also as a body paint and tattoo dye. Today, semi-permanent hair dyes containing Henna as well as its pure dye ingredient HNQ are widely used and have become increasingly popular due to their natural origin.
2-Hydroxy-1,4-naphoquinone(HNQ) was reported to be a weak bacterial mutagen for Salmonella typhimurium strain TA98 or was more clearly mutagenic for strain TA 2637, both in the presence of metabolic activation. HNQ was unable to induce sex-linked recessive lethal mutations in Drosophila melanogaster. The available data suggest that the use of Henna or 2-Hydroxy-1,4-naphoquinone(HNQ) for hair dyeing presents no or negligible risk of genotoxicity to the consumer.
Yellow crystal powder
antifungal, sunscreen, antibacterial, antineoplastic
An antimicrobial antioxidant dye isolated from Henna.
A coloring principle obtained from dried leaves of certain tropical plants (North Africa, India).
Yellow prisms or yellow powder.
Air & Water Reactions
Insoluble in water.
Phenols, such as 2-Hydroxy-1,4-naphoquinone, do not behave as organic alcohols, as one might guess from the presence of a hydroxyl (-OH) group in their structure. Instead, they react as weak organic acids. Phenols and cresols are much weaker as acids than common carboxylic acids (phenol has Ka = 1.3 x 10^[-10]). These materials are incompatible with strong reducing substances such as hydrides, nitrides, alkali metals, and sulfides. Flammable gas (H2) is often generated, and the heat of the reaction may ignite the gas. Heat is also generated by the acid-base reaction between phenols and bases. Such heating may initiate polymerization of the organic compound. Phenols are sulfonated very readily (for example, by concentrated sulfuric acid at room temperature). The reactions generate heat. Phenols are also nitrated very rapidly, even by dilute nitric acid. Nitrated phenols often explode when heated. Many of them form metal salts that tend toward detonation by rather mild shock.
ACUTE/CHRONIC HAZARDS: 2-Hydroxy-1,4-naphoquinone may be absorbed through the skin and can cause skin irritation.
Flash point data for 2-Hydroxy-1,4-naphoquinone are not available but 2-Hydroxy-1,4-naphoquinone is probably combustible.
Henna, prepared by powdering the dried leaves of henna plant (Lawsonia inermis L.), is used for coloring and conditioning hair and nails, particularly by Muslims or Hindus. It contains Lawsone, which very rarely induces contact allergy. Most dermatitis caused by “black henna” is due to PPD and derivatives
Crystallise Lawsone B from *C6H6 or AcOH (m 192.5o, 195-196o). It sublimes in a vacuum (m 194o). It has UV with max at 455nm (aqueous NaOH). [Beilstein 8 H 300, 8 I 635, 8 II 344, 8 III 2543, 8 IV 2360.]
- RARECHEM BW GA 0220
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- CHLOROPHOSPHONAZO III
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