Wednesday, September 8, 2010

Whiffing Aromaticity

Aromatic chemistry.  The very name suggests something sweet and pleasant smelling. I still recall the distinct aromas of purified benzene, toluene, xylene(s), anisole, phenol, benzaldehyde, benzylchloride, aniline, styrene, and naphthalene. It's been over a decade since I whiffed any of those but I'm certain I could score 100% on a blindfolded aroma test for all of them.

Those names are fascinating--despite the stylized suffixes "ene" and "ol".  Many are old words derived from older languages like Greek, Persian, Arabic and those of other ancient trading cultures.  The root words were probably once familiar to everyday people in those cultures, much like the ancient substance called myrrh.  If there were an aromatic hydrocarbon derived from myrrh, I'm certain that chemists would have called it myrrhene.

Few of the aromatics smell bad.  But then again, I've always thought the smell of gasoline was rather pleasant. But some of them smell better than others, especially benzaldehyde (which smells like almond extract) and anisole (which smells like licorice). Not so with the saturated straight-chain hydrocarbons: methane, ethane, propane, butane, pentane, hexane, etc. The odors of those are much fainter.

Aromaticity has a whole nother meaning in chemistry, but that will have to wait for another time.


  1. Remember?

    Every time I walk by my pathologist's histology lab I smell the xylenes used for transferring specimens fixed in paraffin blocks to visual slides.

    Xylenes are synonymous with their otherwise more common product formulation - turpentine.

    These are considered neurotoxic - probably because of their ability to choke off the oxygen in the air moreso than anything else. So it's probably a good thing I never thought of them as especially aromatic, but maybe that's because of the quantity required when used for medical applications is greater than for microscale chemical applications.

    If not, then maybe I should worry about you, Chicklet ;-)

  2. I once tried to distinguish ortho, meta, and para xylene (the three species in xylenes) but could not do so.

    Xylenes are no where near as toxic or carcinogenic as the parent benzene. I heard once that that is because benzene has no easy handle to metabolize.

  3. You're probably right about benzene. Most phase I metabolism (hepatic) and phase II metabolism involves modification of a functional group. Phase II is pretty cool and results in the addition of a moiety up to and including something as complex as an entire glucose molecule.

  4. Sorry, meant to say glucuronic acid instead of glucose. It's been a while. ;-) - Not that they're all that dissimilar, though.