Limonene

**Chemical Properties and Reactions**:
– Limonene is a stable monoterpene that forms isoprene at high temperatures.
– It oxidizes to produce carveol, carvone, and limonene oxide in moist air.
– Dehydrogenation with sulfur leads to -cymene.
– It racemizes at 300 °C and isomerizes to α-terpinene with mineral acid.
– Reacts differently with anhydrous hydrogen chloride and CPBA.
– Biosynthesis involves geranyl pyrophosphate cyclization to form limonene.

**Industrial and Commercial Uses**:
– Commonly used in food, cosmetics, perfumery, and personal care products.
– Acts as a botanical insecticide and organic herbicide.
– Added to cleaning products for fragrance and oil-dissolving properties.
– Used as a solvent in applications like paint stripping and adhesive removal.
– Extracted from citrus fruits and various plant species for industrial production.

**Health, Safety, and Environmental Concerns**:
– Skin irritation potential but generally safe for human use.
– Flammable as a liquid or vapor and toxic to aquatic life.
– Potential health benefits include antioxidant and anti-inflammatory properties.
– Can cause skin irritation, allergic reactions, and respiratory irritation.
– Considered a VOC contributing to air pollution, requiring proper disposal and eco-friendly alternatives.

**Sources and Extraction**:
– Found in citrus fruits like oranges, lemons, and limes.
– Also present in plants such as mint, juniper, and rosemary.
– Commonly extracted from citrus peels through steam distillation.
– Major component of citrus essential oils.
– Industrial production involves extraction from citrus waste and by-products.

**Research, Innovation, and Applications**:
– Ongoing research focuses on therapeutic properties in cancer treatment.
– Innovations in solvent use for various applications.
– Exploration of antimicrobial properties for food preservation.
– Sustainable practices to maximize extraction from citrus waste.
– Collaborations aim to optimize utilization in different sectors.

Limonene (Wikipedia)

Not to be confused with Limonin.

Limonene is a colorless liquid aliphatic hydrocarbon classified as a cyclic monoterpene, and is the major component in the volatile oil of citrus fruit peels. The (+)-isomer, occurring more commonly in nature as the fragrance of oranges, is a flavoring agent in food manufacturing. It is also used in chemical synthesis as a precursor to carvone and as a renewables-based solvent in cleaning products. The less common (-)-isomer has a piny, turpentine-like odor, and is found in the edible parts of such plants as caraway, dill, and bergamot orange plants.

Limonene

Names
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
InChI InChI=1S/C10H16/c1-8(2)10-6-4-9(3)5-7-10/h4,10H,1,5-7H2,2-3H3 Y Key: XMGQYMWWDOXHJM-UHFFFAOYSA-N Y
SMILES CC1=CCC(CC1)C(=C)C
Properties
Chemical formula	C10H16
Molar mass	136.238 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 (ΔcH⦵298)	−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 takes its name from Italian limone ("lemon"). Limonene is a chiral molecule, and biological sources produce one enantiomer: the principal industrial source, citrus fruit, contains (+)-limonene (d-limonene), which is the (R)-enantiomer. (+)-Limonene is obtained commercially from citrus fruits through two primary methods: centrifugal separation or steam distillation.