Limonene



Limonene
IUPAC name 1-methyl-4-prop-1-en-2-yl-cyclohexene
Other names 4-isopropenyl-1-methylcyclohexene
Racemic: DL-limonene; dipentene
Identifiers
CAS number 5989-27-5
SMILES CC(=C)[C@@H]1CCC(=CC1)C
Properties
Molecular formula C10H16
Molar mass 136.24 g/mol
Density 0.8411 g/cm3
Melting point

-95.2 °C

Boiling point

176 °C

Hazards
R-phrases R10 R38 R43 R50/53
S-phrases S61
Flash point 50°C
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references


Limonene is a Racemic limonene is known as dipentene.[1]

Uses

As the main odour constituent of citrus (plant family Rutaceae), d-limonene is used in food manufacturing and some medicines, e.g., bitter alkaloids, as a flavoring, and added to cleaning products such as hand cleansers to give a lemon-orange fragrance. See: orange oil.

Limonene is increasingly being used as a solvent for cleaning purposes, such as the removal of oil from machine parts, as it is produced from a renewable source (citrus oil, as a byproduct of orange juice manufacture.) Limonene works as paint stripper when applied to painted wood. The (R)-enantiomer is also used as botanical insecticide.

The (S)-turpentine-like odor.

Limonene is very common in cosmetic products.

Due to its combustible nature, d-limonene has also seen limited use as an experimental biofuel.[2]

Chemistry

Limonene is a relatively stable terpene, which can be distilled without decomposition, though it forms sulfide.

Limonene occurs naturally as the (R)-maleic anhydride.

It is possible to effect reaction at one of the double bonds selectively. Anhydrous MCPBA occurs at the trisubstituted alkene. In both cases the second C=C double bond can be made to react if desired.

In another synthetic method terpineol.

Biosynthesis

Limonene is formed from geranyl pyrophosphate, via cyclisation of a neryl alkene.

Safety

Limonene and its oxidation products are skin irritants, and limonene-1,2-oxide (formed by aerial oxidation) is a known skin sensitizer. Most reported cases of irritation have involved long-term industrial exposure to the pure compound, e.g. during degreasing or the preparation of paints. However a study of patients presenting dermatitis showed that 3% were sensitized to limonene.[4]

Limonene causes renal cancer in male rats, but not in female rats or in mice of either sex, due to binding of the carcinogenicity or genotoxicity in humans. The IARC classifies d-limonene under Class 3: not classifiable as to its carcinogenicity to humans.[4]

Notes and references

The references in this article would be clearer with a different or consistent style of citation, footnoting, or external linking.
  1. ^ J. L. Simonsen, The Terpenes Volume I (2nd edition), Cambridge University Press, 1947.
  2. ^ Source: European Chemicals Bureau.
  3. ^ J. Mann, R. S. Davidson, J. B. Hobbs, D. V. Banthorpe, J. B. Harborne, Natural Products, pp308-309, Addison Wesley Longman Ltd., Harlow, UK, 1994. ISBN 0-582-06009-5.
  4. ^ a b IARC Monographs on the evaluation of carcinogenic risks to humans 1999, 73, 307-27 [1]
  1. E. E. Turner, M. M. Harris, Organic Chemistry, Longmans, Green & Co., London, 1952.
  2. Wallach, Annalen der Chemie, 246, 221 (1888).
  3. Blumann & Zeitschel, Berichte, 47, 2623 (1914).
  4. Source: CSST Workplace Hazardous Materials Information System.
  5. M. Matura et al., J. Am. Acad. Dermatol. 2002, 33, 126-27.
 
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