Are all pure alkanes, alkenes and alkynes tasteless, odorless and colorless? [closed]








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Non-pure alkanes have a taste.


Are all pure hydrocarbons tasteless, colorless and odorless? Are there hydrocarbons that do have a taste, color and/or odor?


If so, what makes these ones different, even though they are only made of carbon and hydrogen?




Why would a **mixture** of two odourless alkanes have an odour?


As already pointed out by *Greg E* and *Uncle Al*, numerous hydrocarbons without any (heteroatom-based) functional groups do show characteristic smells.


Naphthalene is always remembered for the typical smell of grandma's mothballs.


More pleasant smells are found in the group of **monoterpenes**, i.e. in those molecules with the sum formula $\ce{C10H16}$ that are derived from the combination of two isoprene units. 


![monoterpenes](https://i.stack.imgur.com/i4aKg.png)


These volatile compounds were/are used as fragrances for perfumes. Typical examples are myrcene (**1**), $\alpha$-terpinene (**2**), limonene (**3**), $\alpha$-pinene (**4**), $\beta$-pinene (**5**), $\alpha$-thujene (**6**), sabinene (**7**), and camphene (**8**).




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As far as the colour of hydrocarbons is concerned:


![structure of lycopene](https://i.stack.imgur.com/vZcm1.png)


A sufficiently conjugated system is far from being colourless, take lycopene (**9**), the **deep red** coloured dye in tomatoes as an example.


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Adamantane smells of camphor. n-Nonane is in the scent of some roses, see [here](http://dx.doi.org/10.1016/S0021-9673%2800%2900863-3).


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