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Why Think Up New Molecules?

Adding to the world of known chemical structures is a wonderful mental experiment

Roald Hoffmann

Friendly Sparring

Theoreticians are a minority in chemistry, which remains an experimental science. Our experimental friends and that molecular cornucopia, the evolved biosphere, are so productive. We have been given and have made millions of molecules, with an incredible diversity in their properties. Some are just ringing changes on a theme, some pose real puzzles. So there we are, theoreticians, in a reactive mode, continually asked to explain.

I don't mind explaining. It is one good test of theory, for sure. But it is nice to turn the tables once in a while, and predict.

As it is, experimentalists and theorists have a certain love/hate relationship within any field, not just chemistry. The stereotypes are clear: To the experimentalist, theorists build castles in the air, don't deign to explain what bothers experimentalists, and simplify the world to the extent that it is rendered unreal (as with the "spherical cow" model). To the theorists, experimentalists complicate matters, vary too many factors simultaneously and never measure the observable that the theorists calculate.

It's a game; the "love" part is that both theory and experiment desperately need each other. For the facts are mute. And science, our way of knowing, depends on the coupling of imaginative flights of theoretical fancy with people probing down-to-earth physical and chemical reality.

So … it's fun to make moderately unreasonable predictions of viable or fleeting molecules. The operative part of the phrase is "moderately unreasonable." For if the prospect of synthesis is perceived as taking 20 man- or woman-years, the synthesis will not be attempted. Realistically, the quantum of commitment might be a single Ph.D. student's productive lifetime in graduate school.

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