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Industrial alcohol sold in Taiwan often have a pronounced smell that resembles camphor. When I checked the ingredients at the back, it included tert-butyl alcohol $\ce{(CH_3)_3COH}$, which Wikipedia mentions indeed smells like camphor:

tert-Butyl alcohol is a colorless solid, which melts near room temperature and has a camphor-like odor.

I am wondering why this is, since other similar chemicals such as 1-/2-/isobutanol do not have similar smells, and tert-butyl alcohol doesn't really have much in common with camphor in terms of structure and chemistry.

I recall hearing an explanation of this fact on Quora (which I can no longer find): that tert-butyl alcohol smells like camphor because it has a ball-like shape, which tricks smell receptors in the nose into thinking it is actually a camphor molecule. I am a little skeptical though, since they don't seem structurally similar enough, and if our smell receptors are this rough with sensing molecules, wouldn't it imply a lot of things would smell like one another?

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  • $\begingroup$ A lot of things does smell like one another. $\endgroup$
    – Mithoron
    Commented May 8 at 12:01
  • $\begingroup$ Why does H₂S smell like rotten eggs? We can only answer the How and not the Why. $\endgroup$
    – Baksish
    Commented May 8 at 12:42
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    $\begingroup$ The somewhat spherical shape argument may have some merit. Hexachloroethane smells camphoratious. $\endgroup$
    – user55119
    Commented May 8 at 14:50
  • $\begingroup$ @user55119 yes, do you happen to know any relevant references? By the way, camphoratious is a nice word. $\endgroup$ Commented May 9 at 2:50
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    $\begingroup$ @jono94: It's camphoraCious! C2Cl6 was my "unknown" in qualitative organic analysis 66 years ago. And no, I don't have a reference but I can still smell it. $\endgroup$
    – user55119
    Commented May 9 at 17:35

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They are more similar than you think if you view them using space filling models

Part of the problem in judging how things smell is that smell is a very complex sense. There are possibly hundreds of different olfactory receptors operating in a complex but not fully understood way to enable the ability to distinguish thousands of smells. We really don't fully understand how it all works.

But it seems that some receptors are very specific and some are more general in what they can sense. Combinations of several different receptors may contribute to a specific class of scent.

But, as for the two similar smelling molecules, the secret is to recognise that whatever receptors are responding to the two compounds, the receptor is not reacting to the skeletal chemical structure but to the overall shape of the molecules.

And, if we look at the 3D space filling models of the the two molecules, they are far more similar than the skeletal structures makes them seem. Here are the two compared based on ChemDoodle 3D space filling models:

camphor (CH3)3COH

Presented this way, they both look like large blobs of hydrocarbon on one side with a small polar pocket on the other.

So why our smell receptors think they are similar is not so surprising.

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