Famous Dreamers - Friedrich August Kekulé's 'Structural Theory' & 'Benzene' Dreams

German scientist, Friedrich August Kekulé von Stradonitz (1829 – 1896) is a remarkable figure in the history of chemistry, specifically organic chemistry. In 1856 Kekulé became Privatdozent at the University of Heidelberg. In 1858 he was hired as full professor at the University of Ghent, then in 1867 he was called to Bonn, where he remained for the rest of his career. Twice Kekulé had dreams that led to major scientific discoveries. Kekulé discovered the tetravalent nature of carbon, the formation of chemical/organic "Structure Theory". However, he did not make this breakthrough by experimentation alone, but instead was inspired by the content of a dream sometime between 1856 - 1858. During a speech given at the Deutsche Chemische Gesellschaft (German Chemical Society), celebrating his contributions to organic chemistry in 1890, he outlined his dreams and how they lead to the success of his theory:

I fell into a reverie, and lo, the atoms were gamboling before my eyes! Whenever, hitherto, these diminutive beings had appeared to me, they had always been in motion; but up to that time, I had never been able to discern the nature of their motion. Now, however, I saw how, frequently, two smaller atoms united to form a pair; how a larger one embraced the two smaller ones; how still larger ones kept hold of three or even four of the smaller; whilst the whole kept whirling in a giddy dance. I saw how the larger ones formed a chain, dragging the smaller ones after them, but only at the ends of the chain. . . The cry of the conductor: “Clapham Road,” awakened me from my dreaming; but I spent part of the night in putting on paper at least sketches of these dream forms. This was the origin of the Structural Theory.

Later, in approximately 1865, he had a dream that helped him discover that the Benzene molecule, unlike other known organic compounds, had a circular structure rather than a linear one... solving a problem that had been confounding chemists:

...I was sitting writing on 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 gamboling before my eyes. This time the smaller groups kept modestly in the background. My mental eye, rendered more acute by the repeated visions of the kind, could now distinguish larger structures of manifold conformation; long rows sometimes more closely fitted together all twining and twisting in snake-like 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 also I spent the rest of the night in working out the consequences of the hypothesis.

The snake seizing its own tail gave Kekulé the circular structure idea he needed to solve the Benzene problem. A euphoric Kekulé is claimed to have said to his colleagues: “Let us learn to dream!”