Limonene...a majestic odor in nature!

What is it?
Limonene is a colorless liquid hydrocarbon classified as a cyclic terpene.

Where can we find it?

It is a major constituent in several citrus oils (orange, lemon, mandarin, lime, and grapefruit).

Name
Limonene takes its name from the lemon, as the rind of the lemon -like other citrus fruits- contains considerable amounts of this compound, which contributes to their odor.

Properties
IUPAC name: 1-Methyl-4-(1-methylethenyl)-cyclohexeneMolecular Formula: C10H16
Average mass: 136.234Melting Point: -74.35 °C
Boiling Point:176 °C
Chiral rotation: 87°-102°

Isomerism
Carbon number four of the cyclohexene ring is chiral. Limonene therefore has two optical isomers.

Chiral centres are labelled as R or S using IUPAC nomenclature. But we can found it as d or l or most commonly with (+) or (-).

The two enantiomers have identical chemical properties but different odours.

R-Limonene smells like orange and S-Limonene smells like lemon.

Enantiomers Exception

Although chiral compounds are found as a single optical isomer only, both limonene's enantiomers are produced in nature.

Uses

• Cancer treatment, D-limonene seems to build up in tumors in people with advanced cancer, when it is taken by mouth in 21-day cycles. The high levels of limonene in the tumors may slow down the progress of the cancer, but their effect on the person’s survival is uncertain.
• Cancer prevention (mostly breast cancer)
• Weight loss
• Bronchitis
• Straight solvent replacement
• General purpose cleaners  cleaner for concrete, parking complexes and airport runways, usually clean graffiti off concrete because of its ability to remove paint.
• Grease trap maintainer, helps dissolve grease (butter, cooking oils, meat fat, etc.) and keeps foul odors down in restaurant grease traps.
• Spot and stain remover, can effectively remove ink, oil, grease, paint, tar, bubble gum, and asphalt.
• Hand Cleaners
• Aerosol ingredient, can combine nicely with other aerosol dispenser propellants to impart a pleasant citrus odor.
• Pesticide applications, can effectively kill ants, termites, and other insects on contact
• Extender Flavor and fragrance industry uses fairly large quantities of d-Limonene to extend other more valuable natural oils.
• Help for digestion, metabolism, detoxification and anxiety

Safety
Limonene and its oxidation products are skin and respiratory irritants, and limonene-1,2-oxide (formed by aerial oxidation) is a known skin sensitizer.

Although high doses have been shown to cause renal cancer in male rats, limonene is considered by some researchers to be a potential chemopreventive agent with value as a dietary anti-cancer tool in humans.

The IARC classifies d-limonene as a Group 3 carcinogen: not classifiable as to carcinogenicity in humans: There is no evidence at present that it causes cancer in humans.

How to extract limonene from Orange Peels:

Reference: jahschem.wikispaces.com ~ chm.bris.ac.uk ~ en.wikipedia.org ~ ppiatlanta.com

Extra: You can check my recent publication here.