For a molecule to have a smell it's necessary that the molecule be volatile enough to be in the air. So I think that excludes molecules which are solid at room temperature and atmospheric pressure. Maybe the question then is equivalent to: what is the highest molecular weight organic compound which is liquid at room temperature and atmospheric pressure?

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    $\begingroup$ It can't be a simple as solid vs liquid. Some solids, for example, have distinct odours. Some of these are not, strictly, the odour or the material but of reaction products of the material (osmium has a sharp and dangerous smell because of the formation of osmium tetroxide). And menthol is a solid with a high vapour pressure and a very distinct odour. $\endgroup$
    – matt_black
    Commented Sep 10, 2019 at 12:18
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    $\begingroup$ A smell is not a property of a chemical, but of a nose ability to detect it Without knowledge of threshold partial pressure sensitivity for all compounds, the question cannot be answered. $\endgroup$
    – Poutnik
    Commented Sep 11, 2019 at 5:48
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    $\begingroup$ Wax, as in a candle, has a pretty distinctive smell, and it's pretty big. $\endgroup$
    – Roger
    Commented Sep 11, 2019 at 13:55
  • $\begingroup$ Being solid or liquid is not relevant. Is there a vapor pressure and do the molecules affect the sensors in our [or the dog, cat, butterfly, hyena etc.] sense organs. Even metals have an odor. The question shows a profound lack of observational power and lack of chemical knowledge. $\endgroup$
    – jimchmst
    Commented Dec 14, 2023 at 23:09

2 Answers 2


I'll quote from $\ce{[1]}$:

The general requirements for an odorant are that it should be volatile, hydrophobic and have a molecular weight less than approximately 300 daltons. Ohloff (1994) has stated that the largest known odorant is a labdane with a molecular weight of 296. The first two requirements make physical sense, for the molecule has to reach the nose and may need to cross membranes. The size requirement appears to be a biological constraint. To be sure, vapor pressure (volatility) falls rapidly with molecular size, but that cannot be the reason why larger molecules have no smell, since some of the strongest odorants (e.g. some steroids) are large molecules. In addition, the cut-off is very sharp indeed: for example, substitution of the slightly larger silicon atom for a carbon in a benzenoid musk causes it to become odorless (Wrobel and Wannagat, 1982d).

A further indication that the size limit has something to do with the chemoreception mechanism comes from the fact that specific anosmias become more frequent as molecular size increases. At the “ragged edge” of the size limit, subjects become anosmic to large numbers of molecules. An informal poll among perfumers, for example has elicited the fact that most of them are completely anosmic to one or more musks (e.g. Galaxolide® mw 244.38) or, less commonly, ambergris odorants such as Ambrox®, or the larger esters of salicylic acid.

One can probably infer from this that the receptors cannot accommodate molecules larger than a certain size, and that this size is genetically determined (Whissel-Buechy and Amoore, 1973) and varies from individual to individual.

N.B.: Labdane's molecular formula is $\ce{C20H38}$, which gives a molecular weight (MW) of $\pu{278.5 Da}$ (Da). $\ce{[5]}$ Thus either the $\pu{296 Da}$ value is a typo, or the authors were quoting the MW of a labdane derivative.

Note added in response to answer posted by John Cuthbert (which was a nice find!):

While iodoform, at $\pu{394 Da}$, does indeed exceed the $\pu{>300 Da}$ "general requirement" provided above by Turin & Yoshii, a comparison of its estimated density to that of, e.g., labdane, indicates it's a much smaller molecule (iodoform's three iodine atoms add a lot of mass without a lot of size, at least relative to carbon, hydrogen, and oxygen):

I couldn't find labdane's density, but I found the density of one of its diols (i.e., labdane with an $\text{–OH}$ substituted for $\text{–H}$ in two places). So if we use its density, along with labane's molecular weight, we obtain:

$\pu{MW = 278.5 Da}$, $\pu{\rho = 0.9 g/cm^3}$ $\ce{[6]}$

=> estimated molecular volume ≈ $\pu{510 Å^3}$

Iodoform: $\pu{MW = 393.732 Da}$, $\pu{\rho = 4.008 g/cm^3}$ $\ce{[7]}$

=> estimated molecular volume ≈ $\pu{160 Å^3}$

Even if the density of labdane were, say, 20% higher than that of the diol, we'd get a molecular volume of ≈ $\pu{430 Å^3}$, which is still far above that of iodoform.

This makes it clear that the limiting attribute is physical size rather than molecular weight, and that Turin & Yoshii were using molecular weight as a shorthand surrogate for size. This works reasonably well when comparing oxygenated hydrocarbons, but obviously breaks down when the compounds contain significantly heavier nuclei. As Turin & Yoshii write more precisely at the end of the quoted passage: "One can probably infer from this that the receptors cannot accommodate molecules larger than a certain size." [Emphasis mine.]


$\ce{[1]}$: "Structure-odor relationships: a modern perspective", by Luca Turin (Dept of Physiology, University College London, UK) and Fumiko Yoshii (Graduate School of Science and Technology, Niigata University, Japan), which appears as chapter 13 of: Handbook of Olfaction and Gustation. Richard L. Doty (ed.). 2nd ed., Marcel Dekker, 2003.

$\ce{[2]}$: Ohloff, G. Scent and fragrances: the fascination of odors and their chemical perspectives. Berlin, Springer, 1994.

$\ce{[3]}$: Wrobel D, Wannagat U. SILA PERFUMES. 2. SILALINALOOL. Chemischer Informationsdienst. 13(30), Jul 27, 1982.

$\ce{[4]}$: Whissell-Buechy D, Amoore JE. Letter: Odour-blindness to musk: simple recessive inheritance. Nature, 245(5421):157-8, Sep 21, 1973.

$\ce{[5]}$: https://pubchem.ncbi.nlm.nih.gov/compound/Labdane

$\ce{[6]}$: https://www.chemsrc.com/en/cas/10267-22-8_1640218.html

$\ce{[7]}$: https://en.wikipedia.org/wiki/Iodoform

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    $\begingroup$ Highly enlightening. As per Google, steroids cause body odor but do they have their own distinct smell? $\endgroup$
    – AChem
    Commented Sep 10, 2019 at 3:42
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    $\begingroup$ The chapter from which I quoted indicates they do ["some of the strongest odorants (e.g. some steroids) are large molecules"], though don't know what they smell like. And I found this: ncbi.nlm.nih.gov/pmc/articles/PMC2822864 $\endgroup$
    – theorist
    Commented Sep 10, 2019 at 3:56
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    $\begingroup$ @pentane Sorry, the source from which I'd obtained the chapter incorrectly cited it as coming from the 3rd edition. It's actually from the 2nd edition (see: trove.nla.gov.au/work/29206984?q&versionId=46501355 ). I've corrected this in my answer. A draft of the entire chapter (titled "Structure-odor relations...", rather than "Structure-odor relationships...."; the latter is how it appears in the book's TOC), uploaded by Fumiko Yoshii (the 2nd author), can be found at: researchgate.net/publication/… $\endgroup$
    – theorist
    Commented Sep 11, 2019 at 7:50
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    $\begingroup$ Why does it need to be hydrophobic? Don't odorants solve in water when they are in the nose, so a receptor can detect them? $\endgroup$ Commented Sep 11, 2019 at 11:29
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    $\begingroup$ @cheeesus It's not the water solubility that's important, it's that hydrophobicity implies weak electrostatic interaction and therefore greater volatility. Hydrophilic molecules are polar (and often include hydrogen bond donors or acceptors) and therefore have strong electrostatic interactions among themselves in addition to strong interactions with water. For instance, ethanol, which is polar and acts a both a H-bond acceptor and donor, has a vapor pressure of 5.95 kPa, while propane, a nonpolar molecule with a similar molecular mass and geometry has a vapor pressure of 853.16 kPa. $\endgroup$ Commented Sep 11, 2019 at 21:44

(on behalf of the old-school chemists) Iodoform (393.732 g/mole) has a strong characteristic odour.

  • $\begingroup$ Nice find--thanks! See my edit above. $\endgroup$
    – theorist
    Commented Mar 31 at 2:32

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