Perfumey
moleculeoftheday | November 3, 2008Limonene 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 -…
moleculeoftheday | October 27, 2008Geosmin smells of earth:
You can smell vanishingly small amounts of it, too - mere nanograms of the stuff! It smells this way for a reason - countless soil bacteria busily produce it in your backyard as you read this.
The first thing I thought of when I started this entry was Demeter's Dirt fragrance. I imagine this has to have some of the stuff in it - I've only ever smelled it briefly in Whole Foods, though.
I love smell because I never fail to marvel at the fact that a pure single molecule can exhibit such complex aromas. My favorite example is acetophenone.
moleculeoftheday | September 8, 2008The other day, I was trying to hunt down a tool for the lab. The closest store with any decent complement of tools is one of those big-box stores, so off I went. Unfortunately, I tend to get distracted in the presence of more than a few choices. Somehow, I found myself in the camping aisle, picking up stuff off the rack to read what chemical was in it, and setting it back. A few minutes into doing this, I always wonder: do I look like a shoplifter, someone shopping for ingredients to whip up a fresh batch of drugs, or just a careful shopper? Then, I pulled out the camera phone to take some…
moleculeoftheday | August 7, 2008I love reading lists of fragrance chemicals. The assignment of pleasant, qualitative fragrance descriptions to chemicals with hard-nosed, rigorous functional group names always makes me giggle a little. Acetophenone, for instance, smells of orange blossoms. Today, I came across one that has both in the name: dewy propionate:
The Good Scents Company reports dewy propionate smells of dew, which I think is nonsense. Because odor is subjective, and because a surprising amount of overlap exists between unrelated things, odorants are usually reported with a few characteristics (or more). Flowery,…
moleculeoftheday | January 23, 2008I have to admit, I am a sucker for common names. Why would you grab a bottle of mercury (II) chloride when you could get some "corrosive sublimate"? 3-methylindole? No thanks, give me skatole (named for its smell!). Methyl tert-butyl ketone? Pinacolone (which, sadly, smells like mint). 1,8-bis(dimethylamino)naphthalene? Proton sponge! (R)-2-(4-methylcyclohex-3-enyl)propane-2-thiol? Grapefruit Mercaptan!
Common names make what we do feel more like making potions, and sometimes I'm all for that.
Raspberry ketone is in that vein - it has the above systematic name. Of course, it smells like…
moleculeoftheday | November 13, 2007Valencene is a citrus odorant found in the Valencia orange, hence its name:
It is a terpene, a motif that's ubiquitous in natural products.
moleculeoftheday | August 24, 2007Previously, I covered ethyl thiolactate, which is one of those oddly sweet smelling thiols (like grapefruit mercaptan). Ethyl lactate also smells nice.
Ethyl lactate is the ester of ethanol and lactic acid - Wikipedia claims it's biocompatible, because, after all, you have ethanol and lactate in you. The same is true of ethanol and acetic acid, though, and ethyl acetate is supposed to be moderately toxic. Maybe it's a hydrophobicity thing. Also, lactic acid is chiral, and you've only got one of the two running around.
Anyone have any ideas on those two?
moleculeoftheday | July 31, 2007Hmmm, people don't like being told not to leave certain comments. Thanks for the snark and corrections of the chemical formula. I am off banned drug-related entries for a long while again, they're just not worth the hassle, and there's plenty of worthy molecules out there. Sorry to anyone who felt snubbed; let's talk about a giant ketone!
Civetone is a macrocyclic ketone expressed by an animal that looks photoshopped: the African Civet. It is used in perfumery.
"Macrocycles" are tricky to make - Nature loves five- and six-sided rings, but larger ones, such as civetone, are nearly as hard to…
moleculeoftheday | July 12, 2007It is no secret that I enjoy smelly compounds... a lot. Here's a short list of what I seem to have covered at this blog (hits for "stinky" or "smell"). I'm sure I missed some I've already written up. If I haven't covered your favorite, post a request!
Stinky:
Tosyl Chloride
Triethylammonium Acetate
Ammonium Carbonate
Piperidine
p-Dichlorobenzene
Putrescine
Dimethyl Sulfide
Beta-Mercaptoethanol
Thionyl Chloride
Nice-smelling (or at least inoffensive):
Ethyl Thiolactate
Grapefruit Mercaptan
Hexen-3-al
2-propionyl-1-pyrroline
Muscone
Acetophenone
Isoamyl Acetate
Furfuryl Mercaptan
Ethyl Acetate…
moleculeoftheday | May 3, 2007Brief entry today, watching more debates...
Diacetone alcohol is a common solvent industrially - it is responsible for a substantial portion of the ineffable aroma of Sharpies.
moleculeoftheday | April 11, 2007Yesterday, I covered the intense odorant found in popcorn. Today's molecule is another intense odorant, cis-hexen-3-al.
This molecule has an odor threshold in the high ppt-low ppb neighborhood. It's responsible for the smell of cut grass. Take a look at the Molecule of the Month entry for more information on hexenal odorants.
moleculeoftheday | February 15, 2007Busy couple days. You get some odorants.
For historical reasons, some fragrance contains ingredients inspired by the odor of (or originally found) in a gland in a certain species of false deer. The deer and fragrance are called musk. One substantial contributor to the natural fragrance is muscone:
The deer are endangered, so the overwhelming majority of putative musk you smell is synthetic muscone (or another musk-smelling odorant).
Synthesizing big cyclic molecules is hard ("macrocycles") - closing a long chain of carbons into a ring often results in just making polymers and oligomers ("…
moleculeoftheday | February 5, 2007
Jasmone is an odorant constituent, of, unsurprisingly, jasmine flowers. It's somewhat unique by virtue of its biosynthetic pathway.
Back with a full entry tomorrow.
moleculeoftheday | January 29, 2007I don't have much to say about acetophenone chemically - It is a useful (and very common) synthetic precursor. It's one of a relatively few chemicals that aren't used as a solvent that many labs keep around in liter bottles. The main reason I like it, though, is that it smells wonderful.
Predictably, it is used in perfumery. Like many single chemicals, its smell is puzzlingly hard to pin down (smells, such as coffee, where you definitively say "that's it," are very often mixtures). I'd describe it as something like orange blossom with a bit of artificial cherry/almond.
Acetophenone also is…
moleculeoftheday | October 11, 2006Sorry, but you're hearing about another odorant today:
2E,6Z-nonadienal is an aldehyde responsible for a good chunk of the ineffable aroma of fresh cucumber. Being an aldehyde, it's a bit of a fragile molecule, and doesn't last long in the pickling process, as this blurb explains.
moleculeoftheday | October 10, 2006Isoamyl acetate is a nice, fruity smelling ester - like a lot of the low-molecular weight esters. For this reason, it's used in the flavor and fragrance industry. You won't find it in perfume, though, for two reasons. The first is that esters aren't so hot for perfumery in general. They tend to hydrolyze down to their constituent acid and alcohol (in this case, isoamyl alcohol and acetic acid). The isoamyl alcohol will just smell like solvent; not too unpleasant, but it won't be attractive by any means. The acetic acid will give you a rich vinegary bouquet. For these reasons, esters are…
moleculeoftheday | October 4, 2006Eugenol is a substance found in cloves. In addition to the distinct aroma of cloves, it's responsible for the numbness that clove oil can induce (dentists often swab your gums with it before giving you an injection of novocaine or lidocaine):
Sharp readers will notice the similarity to vanillin. The aromatic nucleus behind both these molecules is guaiacol.
Eugenol is one of those natural products that is sufficiently abundant it can be recovered by steam distillation (PDF).
moleculeoftheday | August 27, 2006These are rare enough that I'm surprised every time I see one. It's a very simple molecule, that apparently makes its way into certain fruit flavorings: ethyl thiolactate.
As you probably have guessed by the numerous references to it, I love the flavor and fragrance field. I don't think I could stand to work in something that's so hit-and-miss, but smell is up there on my favorite-sense list. When a functional group that's normally so notoriously stinky is present in an apparently pleasant molecule, it's always a bit of a shock.
If you've been reading for awhile, you'll remember my entry on…
moleculeoftheday | August 20, 2006Sorry for the short post today, grading and other during-the-academic-year commitments are about to take effect. If you have access, there is a wonderful article in Chemical Reviews ASAP this week:
"The Nose as a Stereochemist. Enantiomers and Odor," by Ronald Bentley. Since it's an ASAP article, there's no page numbers yet, but the url is http://pubs.acs.org/cgi-bin/asap.cgi/chreay/asap/html/cr050049t.html. The DOI is 10.1021/cr050049t S0009-2665(05)00049-X.
For some neat references on chiral odorants, see these MOTD classics:
Grapefruit mercaptan
Carvone
See you tomorrow.