So, as we mentioned yesterday, good old Thomas Midgley had made quite a mess of things with his organolead snafu. By way of apology, he gave us CFCs. Why would we want them?

To make a refrigerator, you need a gas that can go pretty easily between liquid and gas - so, something with a near-room temperature boiling point at atmospheric pressure. If you’re a chemist, you’re thinking: ether, anhydrous ammonia, sulfur dioxide, and a bunch of other nasties. That was, in fact, the stuff we used first (Well, not ether. But loads of SO2 and NH3). Trouble was, it was so toxic it kept killing people. We needed something that balanced volatility with low toxicity.

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Tetraethyllead is another one of those organometallic compounds that is absolutely bizzare unless you work with them yourselves. It’s got lead in it - in fact, it’s over 60% lead by weight, but it’s a clear, lipophilic liquid. It has the effect of decreasing the tendency for gas to combust prematurely in an engine, or “knock.” That is, when added to gasoline, it increases its octane rating. This is all an octane rating is - a measure of a fuel’s propensity to prevent knock. 87 is more likely to knock in a high-compression engine than 91.

Here is the structure of tetraethyl lead:

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Friday, we talked about about carvone. I mentioned that it comes from the same biosynthetic pathway as cholesterol. The precursor to this, as well as a number of other natural products, is isopentenyl pyrophosphate, which we’ll refer to as IPP:

A few things this ends up in are compounds like carvone, limonene, and menthol, shown below:

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Go play outside! See you tomorrow.

The other day we talked chirality. Here’s the example they give in every organic chemistry class when they’re teaching chirality. Carvone!

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Have you ever wondered whether you would swim faster in syrup or water? I hadn’t, either, until I found out someone had actually brought a swimming pool up to to Mrs. Butterworth’s-level viscosity and had people swim in it. Then I became intensely curious.

Proell admits he was slightly taken aback when he first heard Cussler’s proposal to dump 700 pounds of guar gum, a thickening agent, into one of the University’s pools. Fortunately, though, he recognized the proposal’s educational merits.

“Cussler is persuasive, but we didn’t need much persuading. We all agreed that we had an opportunity here to be part of the University’s educational mission. [The experiment] involved movement through water. [I]n aquatics, that’s our business. It intrigued us.”

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A lot of people have heard of “noble gases” - this is that rightmost column of the periodic table: Helium, Neon, Argon, Krypton, and Xenon. They exist pretty much on their own; it is very hard to make a compound out of them, and when you manage to, they’re fleeting sorts of things, waiting to react with whatever’s around.

Another series of noble compounds exists; the noble metals. These are named “noble” for the same reason - their relative lack of reactivity (the idea being that there are “noble” metals that hold onto their electrons in a dignified fashion, and “base” metals that deign to react with the other peasant molecules). Because of their lack of reactivity, they occur as the “native” metal much more often than the base metals (which occur as ores).

All that aside, when you want a metal that won’t react, you’re pretty good with platinum. Platinum is also very high-melting, so the development of a crucible made of platinum was a help, since various things could be heated in it without reacting with their vessel. These are curious objects. If you have any platinum jewelry, you know it really doesn’t wear. Unless it’s polished, though (and Pt crucibles usually are just brushed), it just looks like stainless steel. It doesn’t look like as expensive or special as it is until you pick it up - then you realize it’s denser than gold, and nearly twice as dense as lead - and maybe you are holding something a little bizzare.

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Here is another distinctly unfriendly-looking molecule, arsphenamine. For 30-40 brutish years, this was our single best treatment for syphilis. We owe this distinct pleasure to Paul Ehrlich, father of chemotherapy (coined the term, along with “Magic Bullet.”) In the early 20th century, he was working on histology, or staining cells. He reasoned that if we had compounds that stained only certain types of cells, maybe we could find one that would kill certain cells. Like syphilis spirochetes.

While this was a primitive theory of selectivity, Elrich used it to good effect, and six hundred five dead ends later, he released arsphenamine upon the world:

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Mercury is a weird one. It’s quite toxic, and you’ll do well not to handle it casually, but as the metal it’s actually not that bad. If a thermometer breaks, you can probably clean up the area as best you can, then sprinkle zinc dust or sulfur (disputed, see here) on it to keep it from evaporating. If you spill it in, say, an oven, like in the lab, or spill a great deal, it can be a bigger problem - some labs have mercury bubblers with literally pounds of the stuff in them - for most applications, you can use mineral oil, but especially in academic labs, you see a lot of mercury still floating around.

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Capsaicin is a molecule expressed by chiles (genus capsicum - this includes all pepper fruits, from jalapeno to habanero). It induces the familiar burning sensation. It, or its cousin, dihydrocapsaicin, is responsible for the hotness in essentially all hot sauces. Here is its structure:

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