Odorant chemical information includes our preferred name for the odorant, which appears in large, bold type beneath the top horizontal bar above the pattern. To the right of this name, we provide two common alternative names that are also searched during any searches for odorants by name on our site. To obtain a more complete list of alternative names, we recommend following our link to ChemIDplus, which can be activated by clicking on the Chemical Abstracts Service (CAS) registry number provided beneath the alternative names. The CAS# is unique for each chemical. Beneath the CAS number is the chemical formula and a two-dimensional drawing of the structure. To the right of the CAS number is a link to the OdorDB database at the SenseLab site that is administered by Dr. Gordon Shepherd at Yale University. Clicking this link will search the OdorDB using the current odorant CAS number, returning links to odorant receptor databases, behavioral studies, or fMRI experiments that may have referenced the odorant.  

Underneath the structure drawing, there is a button that pops up a list of molecular properties in a separate window. This window displays measurements and estimates of a number of molecular properties and chemical classifications that might be important in determining both the interactions of odorant chemicals with individual receptors and the spatial organization of responses across the glomerular layer. Values for logP, partial pressure, water solubility, and pKa are modes of all unique values from two Internet databases (Interactive PhysProp Database from Syracuse Research Corporation and the Chemical and Physical Properties Database from the Pennsylvania Department of Environmental Protection) as well as from two chemistry software packages (Molecular Modeling Pro v. 3.14 from ChemSW, Fairfield, CA and ChemDraw Ultra v.6.0 from CambridgeSoft, Cambridge, MA). All other estimates come from calculations performed by Molecular Modeling Pro on modeled structures that had been energy-minimized as discussed below. Because many of these molecular properties are only estimates, we caution against the literal use of any specific value without a more in-depth investigation into the quantity.  

Next to the molecular properties button is another button that launches a rotatable, 3-D model of the odorant structure by way of a Jmol applet. While viewing the Jmol structure, right-clicking (PC) or holding the apple key while clicking (Mac) within the window gives a few options for changing the appearance of the molecule. Another button allows the visitor to download the mol file of the odorant that was used to create the 3D structure. Most 3D molecular modeling and chemical drawing programs can read these files. 

To generate the structures for viewing in 3D and for downloading, we first drew the structures using CS ChemDraw Ultra v.6.0. Usually, this was accomplished simply through the use of the "Convert Name to Structure" option. Occasionally, common chemical names were not recognized by this software, in which case we found the ChemIDplus website from the National Library of Medicine to be a particularly useful source of synonyms, including IUPAC names that are recognized by ChemDraw. The stereoconfiguration of any chiral carbons was made explicit using dashed and solid wedges in ChemDraw before proceeding to the next step, which was to copy the structure and paste it into CS Chem3D Pro v.5.0. Upon pasting, a 3D molecular structure was obtained. We then minimized the energy of this structure under the MOPAC menu option. Typically, we used the default AM1 method with closed shells. (In one case involving the odorant longifolene, this method failed to reach convergence, leading us to use the MM2 method also provided in Chem3D). We then saved the energy-minimized structure as an MDL MolFile, appending the .mol suffix to each filename.  

It should be noted that the energy-minimized structures of odorants are generated by a "quick-and-dirty" method that approximates the most commonly encountered structure of the molecules in the gas phase. It does not account for any effects of solvation by water that are likely to influence the structure of the odorants once they are absorbed in the olfactory mucosa. Also, at room temperature, the odorants will have considerable kinetic energy and may not spend much absolute time in any one conformation. By way of bond rotations and bending, the odorants are likely to shift between multiple relative energy minima, any of which may be relevant to the structure recognized by an odorant receptor. We encourage users of this site to download the structures provided here so that they might use the molecular modeling software of their choice to explore more fully the range of conformations relevant to particular odorants of interest. 

Beneath the odorant chemical structures and buttons is a list of up to four odor descriptors intended to give an impression of the odor perception evoked by the odorant chemical in humans. We have used a number of different sources for these descriptors, including the book Perfume and Flavor Chemicals by Steffen Actander (1994), the Aldrich Flavors and Fragrances Catalog, the book Atlas of Odor Character Profiles by Andrew Dravnieks (1985), the Merck Index, and the Givaudan website. If we could not find four descriptors in these sources, we used Google and the search terms "odor" and the CAS number of the odorant. In the event that multiple sources repeated the same descriptor, we list the descriptor only once. With the exception of the few odorants included in Atlas of Odor Character Profiles, these descriptors are probably not the result of any controlled experiment and therefore should be considered to be anecdotal. On several occasions, the descriptors from one source seemed to be entirely different than the descriptors from a different source, and Arctander documented differences in odor quality for the same chemical caused by differences in concentration and/or purity. Also, there have been few, if any, studies comparing the perception of odor qualities by humans to the perception of odor qualities by rats, although in both species odorants with more similar chemical structures tend to evoke more similar perceptions of odor. It seems likely that distinct odor qualities are experienced by different species depending on species-specific interactions with the natural sources of the odorants.