Friday, February 04, 2005

The O-Ring

You've all heard of ozone (O3) before; it's a reactive gas found in the upper atmosphere of our planet that blocks lots of harmful solar radiation. Discovered first by Christian Schönbein, ozone is used industrially to disinfect bottled water, and clean and bleach clothing. That's all well and good, but not really worth getting into now.

What is news worthy is that a, as-of-yet unobserved, cyclic form of ozone has been predicted to be stable by theorists. It has almost twice as much energy as normal (acyclic) ozone, which means that when the same amount of cyclic ozone combines with hydrogen in a jet engine it produces more energy. That makes it an excellent candidate for the next best rocket fuel for our trips to Mars. If only we had a tank to test.
Temple University's Center for Advanced Photonics Research is trying to make cyclic ozone with their ultrafast lasers. The idea is to take very specifically shaped laser pulses to manipulate single molecules to do what they want. Somewhere in the 10^40 possibilities of pulses there's a path to cyclic ozone. They're relying on a "evolutionary search strategy" to cover this vast search space; how they're doing that we'll have to wait to hear about.

What's really interesting about this molecule is not the promise of being able to make a microgram in a laser system and record its absorbance spectrum (though that would get plenty of chemists hot and bothered). This unknown form of ozone has been predicted to actually be stable. Roald Hoffman (1981 Nobel Prize in Chemistry) discusses some of the reasons for this in a recent article in American Scientist. Coincidentally, some of the reasons that cyclic ozone is likely to be stable are based on the Woodward-Hoffman Rules, for which Hoffman was awarded the Nobel Prize. Hoffman, along with Peter Wolczanski, also recently published a theoretical paper in the Journal of the American Chemical Society discussing the possibility of stabilizing cyclic ozone by complexation to a transition metal.

If the search works out, and this does help put man on Mars, it'll be quite the chemical success story.


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