Limonene
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The limonene C10H16 is a Hydrocarbure Terpène present in many Huiles essential from which it can be obtained by distillation. With room temperature, it is a colorless liquid with odor brilliant, fresh and clean of orange, characteristic of the Agrume S. limonene is in particular used in Parfumerie.
Limonene draws its name from the silt, which, like other citrus fruits, contains considerable quantities of this chemical compound, forming the majority of their perfume.
Limonene is a chiral molecule, and, as it is usual in such cases, the biological sources produce a specific enantiomer. The industrial independent source, the lemon, contains D-limonene ((+) - limonene), which is it ( R ) - enantiomer. Limonene Racémique is known as a dipentene . The second form is the L-limonene, which is it ( S ) - enantiomer.
Uses
As the principal odor which constitutes the citruses (family of the Rutaceae), the D - limonene is used in agribusiness industry like in the drug company to scent the drugs, in particular bitter the Alcaloïde S. It is also used in the products cleaning for their refreshing odor and their effects of Solvant S.Thus, limonene is used also more and more like Solvant, in particular the degreasing of the machines, since it is produced since a renewable source, (the oil of citrus, like a by-product of the manufacture of Jus of orange). Limonene functions as solvent with painting when it is applied to wood.
( R ) - enantiomer is also used like Insecticide.
( S ) - enantiomer, limonene, has to him an odor closer to the pine and Térébenthine.
The use of limonene is very frequent in the products Cosmétique S.
Chemistry
Limonene is a relatively stable Terpène, which can be distilled without decomposition, and forms a Isoprène when one passes a hot metal filament. It is easily oxidized in wet environment in Carveol and Carvone. Oxidation using the Soufre leads to a p Cymène and a Sulfure.Limonene exists naturally like ( R ) - Enantiomère, but can be Racémisé in Dipentène, by simply heating it with 300 °C. At the time it is heated with a Mineral acid, limonene forms a Diène combined, the Terpinène, which oxidize easily out of p Cymène, a aromatic Hydrocarbure. The proof includes/understands the formation of Diels-Alder α- Terpinène when limonene is heated with a maleic Anhydride.
It is possible to selectively carry out the reaction to the one of the two connections. The anhydrous Hydrogène of chloride reacts preferentially to the Alkène désubstitué, whereas the epoxydation with MCPBA arrives at trisubstituted alkene. In both cases, the second C=C doubles connection can make react so desired.
Another synthetic method by Addition Markovnikov of Acide trifluoroacetic followed Hydrolyze of acetate gives Terpineol.
Biosynthesis
Limonene is formed with partirl Geranyl pyrophosphate, via a cyclization of a neryl Carbocation or its equivalent, as shown below. Final The step involves loss off has proton from the cation to form the Alkene.
Safety/Health
The limonene and its products of oxidation are irritating for the skin. limonene-1,2-oxide (formed by simple oxidation with the air) is known like sensitizing for the skin. The majority of the cases of irritation were announced in the long run exposed people in industrial environment to the pure compound (for example, at the time of operation of degreasing before setting in painting). However a study of patients presenting of] shown S.A. that 3% had been sensitized by limonene.
Carcinogenic in the animal: Limonene causes a Cancer of the kidney in the male rat but not in the female (idem in the mouse) because of a bond with the Metabolite limonene-1,2-oxide with α2u- Globulin, a Protein which is produced only by the males.
On does not have a proof that this product is Cancérigène or Génotoxique for the Man. IARC classified the D - limonene under Class 3: not classifiable ace to its carcinogenicity to humans .
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