August Kekulé

The era of structural chemistry dawned with benzene.

Persistence and intuition are the twin pillars of discovery.

As I near the end, I see my work as a thread in the tapestry of science.

I was sitting, writing at my textbook, but the work did not progress; my thoughts were elsewhere. I turned my chair to the fire and dozed. Again the atoms were juggling before my eyes. This time the smaller groups kept modestly in the background. My mental eye, rendered more acute by repeated visions of this kind, could now distinguish larger structures of manifold conformation: long rows, sometimes more closely fitted together; all twining and twisting in snakelike motion. But look! What was that? One of the snakes had seized hold of its own tail, and the form whirled mockingly before my eyes. As if by a flash of lightning I awoke; and this time I also spent the rest of the night in working out the consequences of the hypothesis.

The theory of atomicity, or of the valency of the elements, has become the guiding star of modern chemistry.

Carbon is tetravalent.

The number of atoms which can be united to one atom of carbon is four.

The benzene molecule is a closed ring of six carbon atoms, each united to one hydrogen atom.

The constitution of organic compounds is determined by the number and arrangement of their atoms.

The valency of an element is a constant quantity.

The idea of the 'atomicity' of the elements, or of 'valency' as it is now called, is the foundation of modern organic chemistry.

The properties of a compound depend not only on the nature of its constituent atoms, but also on their arrangement.

The ring structure of benzene is not a static arrangement, but a dynamic one, with the double bonds constantly shifting.

The concept of valency allows us to predict the formulas of new compounds.

The theory of valency provides a simple and elegant explanation for the vast number of organic compounds.

The benzene problem is solved.

The structure of a molecule is not merely a geometric arrangement, but a representation of its chemical behavior.

The dream was the key to the solution.

The true progress of science consists in the discovery of new facts and the development of new theories to explain them.

The atoms are the building blocks of matter.