Tuesday, October 16, 2012

What's Inbetween a Single Bond and a Double Bond?

Anyone who's made it through the gauntlet of organic chemistry may remember that there's not only single bonds and double bonds, but there's "mixture" sort of bonds half way between the two. You can tell how much of a mixture by measuring the bond length accurately; the shorter the bond, the more "double bond" character it has. Measuring these bond lengths can lead to some very pretty pictures, with more pretty pictures here:

I got this one from this blog but it's all over the web in other places as well. It was made by atomic force microscopy looking at a "nanographene" molecule that's basically a collection of fused benzene rings. Each ring is a hexagon with six single-bond sides and three double bonds on top of that. The question is, where exactly do the double bonds spend their time most?

In a single hexagon/benzene ring, the three extra bonds are distributed evenly and each bond is more like a 1.5-bond than a single or double bond. Nanographene is more complex structurally and has more complex patterns of electron-sharing. The IBM researchers found that if you look at the hexagon in the exact center, that those bonds are shorter than the ones radiating out from the center, meaning the electron-sharing is a bit better in the ring in the center, like they're spinning around on the innermost wheel. Like a record player, if anyone remembers those. The "spokes" are a little stretched and are slightly worse bonds.

And I just realized ... this looks like a Settlers of Catan board! The smallest game of Settlers ever may now be possible.

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