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Stink, stank, stunk April 23, 2009

Posted by fetzthechemist in Uncategorized.

My own musings after a post on Carbon Based Curiosities and numerous other comments in various situations on smelly chemicals.

The human nose gets little respect. Its sense of smell is always denigrated and compared to animals. Yeah, so what? Each animal has specialized. Ours is the central receptor system where things are collected and assessed. People can still smell surprisingly low levels and discriminate them from each other.

A colleague in my big-oil days tested this out. Even for pretty mundane smelling cyclohexane, detection was in the tens of parts per billion. For pungent smells that are more distinct, a better signal to noise, it was a part per billion or less – pyridine, butyric acid, methyl-t-butyl ether, mercaptans.

Hydrogen sulfide was low, the nose soon gets saturated and cannot tell the difference in the part per million range between one, five, ten, and so on.

Stinkiest? A matter of taste somewhat, but certain chemicals are biologically hard wired, I think. Skatole, carboxylic acics of ten (or so) carbons or fewer, alpha, omega diaminoalkanes. The first does smell line poop. The second class varies from vomit like to musky goat like and other wonderful smells. The last group is like rotting meat and has wonderful naming – cadaverene, putricine, and such.

In the CBC post, carbonyl sulfide, COS, was mentioned because it imparts smell to carbon disulfide by being a trace impurity. Some of my grad school work involved COS. It is very pungent, but I think has similar effects as hydrogen sulfide on your nose. Lots does not smell that much worse than a little. 

Lots of great smells out there in the chemistry world, too, but that’s another post, maybe.

and finally, the title is a reference to a song in the Christmas TV classic How the Grinch Stole Christmas.



1. organikchemist - April 23, 2009

The fragrance industry is a multibillion dollar/yr industry that gets very little press in the chemical literature. If you strip away the BS fashion glitz that tends to accompany a perfume launch, there is some very interesting chemistry and biology at work. Add to that that some of the ingredients are made on commodity scales (100s tonnes/yr) and it becomes interesting to ponder why fragrance chemistry is an unknown career path.

2. fetzthechemist - April 23, 2009

The whole area of flavors, fragrances, and essences is a facinating field. Smells for pleasure are complex mixtures. There has been a lot of work on separating these mixtures and asceryaining what compound gives what part of it. I have seen many papers where a gas chromatograph outlet is smelled to target peaks (done with a splitter and the other part goes to the MS or FTIR or other conventional detector).

This is a core area the food industry, especially those companies dealing in herbs and spices and flavoring. It is also important in characterizing wines (I saw one last autumn by an Australian group on what gives shiraz its spicy flavor).

There is an American Chemical Society division, I think, that focuses on fragrances and flavors, or maybe it is a subdivision of the Food Chemistry division. I do not know what they do to attract people, but it would be a very interesting career path.

3. psi*psi - April 24, 2009

Wasn’t there also a group several years back that was using braconid wasps (so cute!) to detect low levels of some compounds? I wonder what their detection limit was.

4. fetzthechemist - April 24, 2009

That does ring bells. I think they were keying in on which compounds were the pheromones. I remember that sex and food attractants for insects are way, way down in the parts per quadrillion and quintillion ranges.

Years ago, when this first popped up, I remember a Dutch group used grad student nose detectors. I guess the noxious or toxic components were just a part of getting degree.

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