Guaiazulene, also azulon or 1,4-dimethyl-7-isopropylazulene, is a dark blue crystalline hydrocarbon. A derivative of azulene, guaiazulene is a bicyclic sesquiterpene that is a constituent of some essential oils, mainly oil of guaiac and chamomile oil, which also serve as its commercial sources. Various soft corals also contain guaiazulene as a principal pigment. Its low melting point makes guaiazulene difficult to handle, in contrast to the crystalline nature of the parent azulene. The electronic structure (and colors) of guaiazulene and azulene are very similar.
The blue color of the mushroom Lactarius indigo is due to the guaiazulene derivative (7-isopropenyl-4-methylazulen-1-yl)methyl stearate.

Appearance and properties: dark blue solid

Density: 0.976 g/mL at 25 °C(lit.)

Boiling point: 153 °C7 mm Hg(lit.)

Melting point: 27-29 °C(lit.)

Flash point: >230 °F

Refractive index: 1.4985 (25oC)

Stability: Stable under normal temperatures and pressures.

Storage condition: 2-8oC

Vapor pressure: 0.00148mmHg at 25°C

Production method

Blue camphor oil (distillation range 220 ~ 300℃) was extracted by nitrogen and palladium carbon reagent, boiling reaction for 5h, and petroleum ether and 80% phosphoric acid were added to the filtered oil. After the acid layer is washed with petroleum ether, a large amount of ice water is added and extracted with petroleum ether. After the organic phase was washed with 2% sodium hydroxide and water, the concentrated product was guaiacum crude, and the yield was 8% according to blue camphor oil.

Use

Guaiaco is a cosmetic additive approved by CTFA, which can relieve skin irritation and allergic reaction of other substances. It is a common topical anti-allergy agent with obvious anti-inflammatory function, and is used in sunscreen products to prevent or treat sun burns. Can be antibacterial, oral hygiene products added 0.1% can inhibit microbial growth. Guaiac can also be used as a cosmetic pigment.