Linalool

=**Linalool**=



Also known as linalyl alcohol, linaloyl oxide, allo-ocimenol, β-linalool, //p//-linalool, and 2,6-dimethyl-2,7-octadien-6-ol. The molecular formula of Linalool is C 10 H 18 O.

Linalool has two stereoismers. Stereoismers are isomeric molecules - compunds that have the same molecular formula but different structural formulas. Stereoismers differ from each other only in their three-dimensional orientation of atoms in space. Linalool's stereoismers are also enantiomers, which are molecules that are mirror images of each other and thus not identical. These enantiomers are **licareol**, or (R)-(-)-linalool, and **coriandrol**, or (S)-(+)-linalool. Both enantiomers are found in nature. Licareol is found in plants such as coriander, palmarosa and sweet orange flowers, and coriandrol is found in plants such as lavender, bay laurel and sweet basil.



Linalool is found in over 200 species of flowers and spices, including mints and scented herbs, cinnamon, rosewood and citrus fruits. It is used in 60%-80% of perfumed cleaners and hygiene products as a scent. Products linalool is found in include soaps, detergents, shampoos and lotions, and flea and cockroach insecticides. Vitamin E is also a common product of linalool.

Linalool oxidizes when exposed to oxygen. This oxidized form can cause allergic reactions in some humans, so minimizing exposure to the chemical is encouraged.

Recent study revealed that many people are allergic to air oxidized form of the linalool, a fragrance ingredient. Linalool is added in many shampoos, skin conditioners and soaps but it is naturally found in lavender, mint, and other plants. Researchers found that 5 percent and 7 percent people out of 3,000 study subjects were allergic to oxidized linalool. Eczema can lead to rashes, swelling, itching and cracking.



Biosynthesis
In higher plants linalool, as other monoterpenoids, is produced from isopentenyl pyrophosphate via the universal isoprenoid intermediate geranyl pyrophosphate, through a class of membrane-bound enzymes named monoterpene synthases. One of these, linalool synthase (LIS), has been reported to produce (S)-linalool in several floral tissues.

Enantiomers
Linalool has a stereogenic center at C3 and therefore two stereoisomers: **licareol** is (//R//)-(–)-linalool with CAS No. 126–90–9 (PubChem 67179) and **coriandrol** is (//S//)-(+)-linalool with CAS No. 126–91–0 (PubChem 13562).

Both enantiomeric forms are found in nature: S-linalool is found, for example, as a major constituent of the essential oils of [|coriander] (//Coriandrum sativum// L. family [|Apiaceae] ) seed, [|palmarosa] [//Cymbopogon martinii// var martinii (Roxb.) Wats., family [|Poaceae] ], and [|sweet orange] (//Citrus sinensis// Osbeck, family [|Rutaceae] ) flowers. (R)-linalool is present in [|lavender] (//Lavandula officinalis// Chaix, family [|Lamiaceae] ), [|bay laurel] (//Laurus nobilis//, family [|Lauraceae] ), and [|sweet basil] (//Ocimum basilicum//, family [|Lamiaceae] ), among others. Each enantiomer evokes different neural responses in humans, and therefore are classified as possessing distinct scents. 3S-(+)-linalool is perceived as sweet, floral, petitgrain-like (odor threshold 7.4 ppb) and the 3R-form as more woody and [|lavender] -like (odor threshold 0.8 ppb)

Uses
Linalool is used as a scent in 60–80% of perfumed hygiene products and cleaning agents including soaps, detergents, shampoos, and lotions. [|[1]] It is also used as a [|chemical intermediate]. One common downstream product of linalool is [|Vitamin E]. In addition, linalool is used by pest professionals as a flea and cockroach insecticide. Linalool is used in some mosquito repellent products, however the EPA notes that: "A preliminary screen of labels for products containing Linalool (as the sole active ingredient) indicates that efficacy data on file with the Agency may not support certain claims to repel mosquitos." [|[2]] Akio Nakamura together with colleagues from the University of Tokyo and T. Hasegawa Co., Ltd in Kawasaki, Japan, claim to have demonstrated that inhaling linalool can reduce stress in lab rats. In a study published in The Journal of Agriculture and Food Chemistry, [|[3]] they exposed the animals to stressful conditions and found that those inhaling linalool saw their stress-elevated levels of neutrophils and lymphocytes fall to near-normal levels compared with the controls. Inhaling linalool also reduced the activity of more than 100 genes that "go into overdrive" in stressful situations. The findings could form the basis of new blood tests for identifying fragrances that can soothe stress, the researchers claim.