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Monday, October 1, 2012

August Kekule


Encyclopedia of World Biography on Friedrich August Kekulé

The German chemist Friedrich August Kekulé (1829-1896) was the founder of structural organic chemistry.
August Kekulé, later Kekulé von Stradonitz, was born on Sept. 7, 1829, in the city of Darmstadt. After studies in the local gymnasium, young August, obedient to his father's wishes, enrolled in the school of architecture at the University of Giessen. At school Kekulé demonstrated a great talent for mathematics and drawing. It was in chemistry, however, a discipline then grappling with the complexities of the structure of organic molecules, that Kekulé's mathematical bent, excellent memory, and sense of space made him an ideal student of baffling structural problems.
Supported by his affluent family, Kekulé was able to study in Paris, where he gained the friendship of the eminent chemist Charles Gerhardt, from whose theory of types he later evolved his own theory of valency. He also moved in the scientific circles of Jean Baptiste Dumas and Charles Wurtz, whose school of organic chemistry was the only one in Europe that was able to rival the later German institutes. After his Paris studies Kekulé moved to London, where he worked as an assistant to John Stenhouse and later worked with William Williamson and Reinhold Hoffmann. From 1855 to 1858 Kekulé followed up his apprenticeship by serving as privatdozent at Heidelberg. Later in 1858 he was professor of chemistry at Ghent and ended his scientific career at the University of Bonn, where he served from 1867 until his death on July 13, 1896. During this long tenure Kekulé contributed to the spectacular rise of organic chemistry and the chemical industry of Germany. His students came from all over Europe and went out to take leading professorships and to head industrial laboratories.
Kekulé was not a master experimentalist, but he became an inspired pedagogue. His mind was keyed to the problems of theory, particularly to the understanding of the architecture of the scores of new organic molecules that chemists were isolating from the plant and animal worlds and creating in their laboratories. It was Kekulé who brought order out of this chaos by grasping the fact that the secret of organic chemistry is contained in the tetravalency of the carbon atom and that this element has the unique capacity to link in long chains, with endless isomeric combinations possible.
Kekulé's supreme contribution to organic chemistry grew out of his solution to the problem of the structure of benzene (C6H6), the simplest of the aromatic series of carbon compounds. His solution to this puzzle, as told in his own words in 1865, was: "There I sat and wrote my Lehrbuch, but it did not proceed well, my mind was elsewhere. I turned the chair to the fireplace and fell half asleep. Again the atoms gamboled before my eyes. Smaller groups this time kept modestly to the background. My mind's eyes, trained by visions of a similar kind, now distinguished larger formations of various shapes. Long rows, in many ways more densely joined; everything in movement, winding and turning like snakes. And look, what was that? One snake grabbed its own tail, and mockingly the shape whirled before my eyes. As if struck by lightning I awoke. This time again I spent the rest of the night working out the consequences." From the dream of Kekulé had emerged the now familiar ring structure of benzene.