What kind of molecules do I smell when draining cooked potatoes or rice? When I drain potatoes after cooking them, they exhibit a nice smelling odor. It is not very strong. Now I know that some perfumes use natural molecules and one of them could come from potatoes (or rice.) But I forgot what the name was for this molecule, or perhaps someone knows some perfumes using these kinds of compounds.

It would be interesting to know what the functions of such molecules are in the organisms. Just an enzyme, or possibly an attracting force for some reason?
What a good question. But unanswerable by me and my prior knowledge and skill in google-fu. I have some general answers. This is a complicated area, since smell is both a physical issue and an individual and unmeasurable issue. Olfactory science is at a surprisingly basic level, given how far we are generally. I tried investigating what compounds in rice provide odour, the answer seems to be; way more than I could possibly have thought. Check out this article - while it is rough to digest a scientific articl unless you have basis knowledge just look at that list at page 505-506. There are many aromas in rice!

As for what functions they perform - looking at the list it is probably impossible to generalize down to what functions such a wide array of compounds do. Certainly, some compounds that are odorous has a primary function of being odorous, attracting pollinators and attracting mates. For rice, which has been around humans since time immemorial (at least 9k BC) they have probably been through a selection process, the most benevolent smelling rice plants being selectively bred, but this is speculation on my part. Other compounds have other functions and just happen to have a strong odour. Generally, to be odorous, the compound must have some volatility. What can also be said generally and very broadly is that alcohols and aldehydes / ketones are more often odorous than other compounds. There are also certain inorganic compounds that are (and often strongly so), Ammonia, Sulfide and the "garlic" series (S-Se-Te) for instance.

Good question. If you learn more, let us know.