Linalool is a terpene. The chemical formula is C10H20O. Natural essential oils contain dextrorotatory or levorotatory linalool and racemic forms. Dextrorotatory linalool is mainly present in cineole, citronella oil, and eucalyptus oil; levorotatory linalool is mainly present in rose oil and the essential oils of the genus Pelargonium. The melting point of dextrorotatory linalool is 244.4°C, the relative density is 0.8590 g/cm³ (20°C), and the specific rotation is 6.8°. The melting point of levorotatory linalool is 108-109°C (10 mmHg), the density is 0.859 (18/4°C), and the specific rotation is -5.3°. Both are colorless liquids with a sweet rose-like fragrance, and the fragrance of the levorotatory form is purer than that of the dextrorotatory form. It is soluble in alcohol and medicinal ether. Linalool is more stable than geraniol. Linalool can be converted into linalool aldehyde by dehydrogenation or oxidation.

Dextrorotatory and racemic linalool are produced by partially manufacturing them from citronellal in single essential oils; they can also be produced from dextrorotatory or racemic geraniol in single essential oils; they can also be obtained by esterifying a portion of the geraniol and nerol compounds formed; or by reacting isopropanol with barium-active chromic acid copper under pressure at 180°C, with a yield of 90%, which is an industrial production method; or they can be produced from pinene with electronic optical specificity to manufacture linalool with the (-) configuration.

Main applications of linalool

1. It has a more elegant rose-like fragrance than geraniol and is an essential raw material for preparing various rose-type aromatic fragrances. It can be used in a variety of skincare fragrance products.

2. It is easy to undergo esterification reactions with citric acid.

Methods of generating linalool

(1) Dextrorotatory and racemic linalool are produced by partially manufacturing them from citronellal in single essential oils. The dextrorotatory citronellal obtained from the steam distillation of java lemongrass oil is esterified with lanthanum nickel metal catalyst to become dextrorotatory linalool. Similarly, racemic linalool is obtained from a portion of the racemic citronellal in eucalyptus oil.

(2) It is produced by manufacturing dextrorotatory or racemic geraniol from single essential oils. The ginger alcohol obtained from java citronella oil is catalytically hydrogenated and then distilled to obtain it. The use of lanthanum cobalt as a metal catalyst can esterify the 2-position alkyl groups.

(3) It is obtained by esterifying a portion of the geraniol and nerol compounds formed; or by reacting isopropanol with barium-active chromic acid copper under pressure at 180°C. The yield of this method is 90%.

(4) The linalool is produced by manufacturing the (+)-linalool from pinene with electronic optical specificity. The α- or β-pinene is esterified to obtain (-)-cis-pinane, which is catalytically cracked to (+)-3,7-dimethyl-1,6-octadiene, and reacts with triisobutyl aluminum or diisobutyl aluminum hydride. Subsequently, the alcohol aluminum obtained is oxidized and hydrolyzed to obtain linalool with a purity of 97%.