Why Think Up New Molecules?
Adding to the world of known chemical structures is a wonderful mental experiment
Theories are fecund webs of understanding. They come to be accepted by scientific communities for many reasons, but certainly the trait of making predictions, preferably risky ones, is an important factor in why people buy into theories.
Could one imagine a better probe of our comprehension of protein catalytic function than the design of an enzyme that, say, flips on its head the selectivity of a catalyzed reaction, or that turns over molecules faster than the natural one? If you have a theory of superconductivity, a super way to demonstrate your understanding would be not only to explain the observed isotope effects and the symmetry properties of the phenomenon, but also to predict what chemical compound should be a high-temperature superconductor. We're not there.
The consistent theoretical prediction of viable molecules with unusual structures or properties is the best test of the degree of understanding science has achieved.