Muscone (Sixty percent of the time, it works every time!)

Busy couple days. You get some odorants.

For historical reasons, some fragrance contains ingredients inspired by the odor of (or originally found) in a gland in a certain species of false deer. The deer and fragrance are called musk. One substantial contributor to the natural fragrance is muscone:

The deer are endangered, so the overwhelming majority of putative musk you smell is synthetic muscone (or another musk-smelling odorant).

Synthesizing big cyclic molecules is hard ("macrocycles") - closing a long chain of carbons into a ring often results in just making polymers and oligomers ("intermolecular" reactions). One early way of closing rings on themselves ("intramolecular" reactions) was to perform the reaction at high dilution. An example is illustrative:

Take an empty swimming pool and fill it 10% of the way up with snakes. Observe how the snakes are much more likely to bump into each other than curl up on themselves. This is analogous to an intermolecular reaction.

Obtain a second swimming pool and fill it 90% of the way with water. Now dump the same number of snakes in. If necessary, you can reuse the snakes from part 1. Observe how the snakes are much less likely to bump into one another, and many will end up touching part of themselves with another part of their body. This is analogous to an intramolecular reaction. As go snakes, so go long chains of carbon.

Synthesizing macrocycles isn't easy, although we've gotten much better at it. Observe, for example, this recent paper on the synthesis of muscone!

Fair warning: in case you didn't catch it, "Sixty percent of the time, it works every time" is an Anchorman reference. It was intentional, and it was probably obvious to most, but the more I notice plagiarism, the more I feel funny about not pointing out anything with the possibility of appearing untoward. I don't want to go down as "Frat Pack Plagiarist."