These are rare enough that I'm surprised every time I see one. It's a very simple molecule, that apparently makes its way into certain fruit flavorings: ethyl thiolactate.
As you probably have guessed by the numerous references to it, I love the flavor and fragrance field. I don't think I could stand to work in something that's so hit-and-miss, but smell is up there on my favorite-sense list. When a functional group that's normally so notoriously stinky is present in an apparently pleasant molecule, it's always a bit of a shock.
If you've been reading for awhile, you'll remember my entry on grapefruit mercaptan, another sweet-smelling thiol. Most thiols end up smelling somewhere between burning tires and garlic (these being both rich in volatile sulfur compounds themselves). The smell of thiols tends to linger, as well. One memorable afternoon, a slightly careless colleague was using some 1,3-propanedithiol to protect a ketone (like so). He somehow spilled it in the drawer containing a bunch of rubber items (which tend to soak up stink pretty well), so we had to deal with a whiff of that every time we opened the drawer for awhile. Funny thing is, it seemed to throw off my ability to enjoy all sulfrous scents for awhile - carmelized onions, which I normally like, were noxious.
Another reason for writing this column was that I wanted to drop in a xkcd comic. Since chemistry comics are hard to come by for some reason, you see.
If you don't get it, click here.
Note that they are alluding to the bizzare grapple, which doesn't taste like grape at all - more like grape Kool-Aid. See you tomorrow.
I actually groaned aloud while reading that xkcd comic, but not as loudly as I did while reading this one.
And yeah! When I saw the morpheme "thiol-" in today's post I thought we were going to get another paragraph about how amazingly evil this molecule smelled, but then I saw the word "sweet"! Crazy!