Limonene

Limonene

Skeletal structure of the (R)-isomer Ball-and-stick model of the (R)-isomer Limonene (R)-isomer
Limonene extracted from orange peel
Names
Pronunciation	/ˈlɪmənˌiːn/ LIM-uh-neen
Preferred IUPAC name 1-Methyl-4-(prop-1-en-2-yl)cyclohex-1-ene
Other names 1-Methyl-4-(1-methylethenyl)cyclohexene 4-Isopropenyl-1-methylcyclohexene p-Menth-1,8-diene Racemic: DL-Limonene; Dipentene
Identifiers
CAS Number	138-86-3 (R/S) Y 5989-27-5 (R) Y 5989-54-8 (S) Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:15384 Y
ChEMBL	ChEMBL449062 (R) Y
ChemSpider	20939 (R/S) Y 388386 (S) Y 389747 (R) Y
ECHA InfoCard	100.004.856
KEGG	D00194 Y
PubChem CID	22311 (R/S) 439250 (S)
UNII	9MC3I34447 (R/S) Y GFD7C86Q1W (R) Y 47MAJ1Y2NE (S) Y
CompTox Dashboard (EPA)	DTXSID2029612
SMILES CC1=CCC(CC1)C(=C)C
Properties
Chemical formula	C10H16
Molar mass	136.24 g·mol−1
Appearance	colorless liquid
Odor	Orange
Density	0.8411 g/cm3
Melting point	−74.35 °C (−101.83 °F; 198.80 K)
Boiling point	176 °C (349 °F; 449 K)
Solubility in water	Insoluble
Solubility	Miscible with benzene, chloroform, ether, CS2, and oils soluble in CCl4
Chiral rotation ([α]D)	87–102°
Refractive index (nD)	1.4727
Thermochemistry
Std enthalpy of combustion ΔcHo298	−6.128 MJ mol−1
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Skin sensitizer / Contact dermatitis – After aspiration, pulmonary oedema, pneumonitis, and death
GHS labelling:
Pictograms	‍‍‍
Signal word	Danger
Hazard statements	H226, H304, H315, H317, H410
Precautionary statements	P210, P233, P235, P240, P241, P242, P243, P261, P264, P272, P273, P280, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P312, P333+P313, P362, P370+P378, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)	2 2 0
Flash point	50 °C (122 °F; 323 K)
Autoignition temperature	237 °C (459 °F; 510 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Limonene is an organic compound. It is one of the most common monoterpenes. It is used as a food additive and as a

Structure

Limonene is a chiral molecule with two stereoisomers, (R)-limonene and (S)-limonene. Both of them are found in nature, but the (R) isomer is more common.

Occurrence and production

(R)-Limonene is found in the peel of citrus fruits like oranges and lemons. Up to 95% of citrus essential oil is made of limonene. The pure chemical is made by steam distillation of citrus peel or essential oil. Most limonene is produced as a byproduct of the orange juice industry.

(S)-Limonene is sometimes incorrectly associated with lemons, and claimed to be the cause for the different scents of lemons and oranges. In reality, both oranges and lemons contain (R)-limonene. The (S) enantiomer is found some spices like caraway, dill, and bergamot.

Biosynthesis

Limonene is one of many natural terpenes made from geranyl pyrophosphate.

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The two stereoisomers of limonene are made by separate enzymes, (R)-limonene synthase and (4S)-limonene synthase.