Molecules: You'd better learn to live with them.
Limonene is a monoterpene that occurs in citrus peel, and it has a strong generic citrus smell. Many terpenes are smelly, like carvone (spearmint or caraway). Interestingly, limonene is cheap and abundant enough to use as a semi-green degreaser or solvent.
Green or not, limonene isn't totally safe. You can actually get sensitized to it - essentially developing an allergy - and then you're in the unpleasant position of being allergic to citrus peels. Careful lab technique and a certain amount of luck have allowed me to avoid sensitization to any lab chemicals. And that's a great thing - everyone I've talked to who was appreciably sensitized to a chemical said it seemed to turn up EVERYWHERE after that.
Please, share your sensitization stories below!
Physical Science
Life Science
Comments
Limonene is a by-product of industrial-scale orange juice production. Thus, it is only produced in places where orange juice, frozen concentrate (FC) or not from concentrate (NFC) organge juice, is made. Only two places make commercial quantities of limonene - the Sao Paulo region of Brazil and the Florida citrus belt.
To say limonene is "cheap and abundant" is really a matter of perspective. Limonene has many industrial uses including, solvent, aroma chemical, flavor raw material, and the least known but most versatile use: raw material for polymer production.
A variety of polymeric resins can be made whose uses span from chewing gum to industrial adhesives. In these applications limonene replaces non-renewable petrochemicals like dicyclopentadiene and piperylene. If limonene were more abundant and less expensive than it is today it could be used to a much greater extent to diminish our reliance on a range of petrochemicals.
Posted by: Marc Jackson | November 4, 2008 8:45 AM
So, given that I'm allergic to orange blossoms and that peeling an orange makes my nose itch like crazy, would that be the limonene causing the reaction? It really sucks because I live in central Florida, which used to be one giant orange grove.
Posted by: CyberLizard | November 4, 2008 9:49 AM
"...use as a semi-green degreaser or solvent." Sure, it starts out "green", but after you've added your grease to it, it's no longer green.
Sorry, no sensitization story here either!
Posted by: John | November 4, 2008 10:59 AM
Carvone is *spearmint* or caraway. Wintergreen is methyl salicylate.
Chemical sensitization is serious. A guy name Craig could detect Cp from Diels-Alder undergrad labs a mile upwind. He began his alkaloid thesis cracking a gallon of Cp-dimer and peroxidizing it. Imagine a well-paying career sitting downwind of a refrigerator factory accompanied by an epinephrine syrette. He should have gone for it.
Posted by: Uncle Al | November 4, 2008 12:56 PM
Fixed, thanks Al.
Posted by: Molecule of the Day | November 4, 2008 4:45 PM
Is that the stuff used to make the hand cleaner "Fast Orange"? Maybe I shouldn't be smearing it on my body?
Posted by: Blind Squirrel FCD | November 4, 2008 5:27 PM
I used it in warm water to eliminate pet fleas one summer. It was effective, but bathing the pets wasn't fun.
Posted by: kirsten | November 6, 2008 5:43 AM
Limonene is actually a monoterpene.
Posted by: Bunsen Honeydew | November 6, 2008 12:32 PM
You're talking about the racemic mixture. What about the individual enantiomers? I wonder if they have different properties.
Posted by: ladytomorrow | November 7, 2008 9:58 AM
Aren't lemon and lime oils isomers of limonene?
Posted by: justawriter | November 7, 2008 2:59 PM
Pine-Sol is a cleaner made from pine oil, correct? I think the main component is a similar molecule called pinene. Again, it can be distilled from plant source (pine needles, bark, sap).
Posted by: Vince Noir | November 7, 2008 3:32 PM
Fixed, thanks Bunsen.
Posted by: Molecule of the Day | November 7, 2008 7:24 PM
the only difference between the enantiomers is the smell as far as i remember.
Posted by: mellor | November 22, 2008 4:42 AM
Limonene is also used in the manufacture of mace and pepper spray. Being both a skin irritant and sensitizer it synergistically helps the irritation effects of the pepper.
Posted by: Skippy | December 11, 2008 11:07 AM
Limonene is monoterpene, it has two isomer i.e. L-Limonene(Ex-Mint Oil),D-Limonene(EX-Orange)
Posted by: sanjeev Lahankar | May 11, 2009 4:08 AM