Geraniol

• Lemonol
• Geranyl

Colorless or slightly yellowish liquid with a flowery smell

Liquid

0.89 g · cm -3

-15 ° C

229-230 ° C

27 Pa (20 ° C)

Poorly soluble in water

1.4766 (20 ° C)

Attention

3600 mg · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

Is an acyclic monoterpene geraniol, allyl alcohol, and is in the E / Z isomerism at Nerol Geraniol is the E isomer, Z- isomer nerol. As a floral note, it is a component of many perfumes. Geraniol is an intermediate in the preparation of Geranylestern, citronellol and citral.

Occurrence

It is part of most essential oils and comes including in coriander, bay leaf, and nutmeg before.

The largest amounts are in palmarosa oil ( Cymbopogon martinii, 70-85 %) contain the oil of geranium and rose.

Production and representation

On an industrial scale is the most convenient method of preparation hydrogenation of citral. Smaller amounts are for the perfume industry from the distillation of Javanese citronella, may, with the prior hydrolysis of the ester obtained. Another synthetic route is the isomerization of linalool in the presence of catalysts orthovanadate and subsequent separation of nerol by fractional distillation in yields over 90 percent.

Properties

Physical Properties

Geraniol is a colorless to slightly yellow liquid with a flowery rose - like odor. The density is 0.88 g of geraniol · cm -3. The liquid solidifies at about -15 ° C and boils at about 230 ° C. In water, it is poorly soluble at 686 mg · l -1. The flash point is 76 ° C.

Chemical Properties

As acyclic unsaturated alcohol is geraniol a rearrangement and cyclization reactions. Rearrangement in the presence of copper catalysts leads to citronellal, partial or complete hydrogenation to citronellol or 3,7- dimethyloctane -1-ol, or the oxidation catalytic dehydrogenation to citral, esterification to the corresponding Geranylestern. In the acidic environment can geraniol as well as nerol to the isomer α -terpineol cyclize.

Biological Significance

While geraniol itself is only a weak contact allergen, its auto-oxidation products have a much stronger allergenicity.