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Famous scholars from Kiel:

Ludwig Claisen

Brilliant chemist, headstrong person: Ludwig Claisen spent seven years at Kiel University.

Ludwig Claisen is known beyond Germany’s borders for his discoveries in the field of organic chemistry, at least amongst chemists: the Claisen condensation »was a fundamental discovery, which is imparted to every first-year student in the organic chemistry field. It is so fundamental that the name of the person making the discovery is often no longer even mentioned«, says Professor Günter Paulus Schiemenz from the Institute for Organic Chemistry. This also applies to the Claisen rearrangement. A rearrangement is a reaction, during which a new chemical compound is created through the regrouping of a molecule, in this case a carbonyl compound. It was only recognised much later that Claisen’s discovery contained a cross-linking reaction for a fundamental principle of reaction. Fame and awards were therefore gathered by those who carried out further research with Claisen’s principles, for example the American chemist Roald Hoffmann, who was awarded the Nobel Prize for this in 1981. Claisen himself had been born more than a century earlier in 1851, in Cologne. After completing his schooling, Claisen moved to Bonn for his scientific studies, where he studied for his doctorate under the renowned chemist Friedrich August Kekulé and qualified as a professor in 1878. Various postings followed: Manchester, Munich, Aachen.

In 1897 he was offered a chair in Kiel, which he accepted but not wholeheartedly. He was reluctant to leave his mother behind in the Rhineland, as she was 80 years old at the time, and was also unhappy at the thought of having to give the major lecture on inorganic experimental chemistry in Kiel. This was not his field. Nevertheless he took up his position as Professor of Chemistry here on 1 October 1897. He found the harsh climate difficult to cope with. All his life he had problems with his heart and lungs. His colleague at the time Professor Heinrich Blitz wrote this about him: »Claisen was a man of noble disposition, with great consideration for others, quiet and even-tempered; reserved. A typical old bachelor, who was concerned about his health and lifestyle.« In the middle of 1898 Claisen suffered such serious pneumonia that he momentarily considered giving up his profession. At the end of the same year he was appointed Privy Councillor (Geheimer Regierungsrat). Three years later his mother died; he had written to her every day from Kiel, and then Claisen was even expected to deal with the reorganisation of the Institute. It was too much for him. He felt pains in his head, dizziness and breathlessness. He retired and had an unconventional move out of the Kiel Institute in 1904. He later reported that when he wanted to leave his apartment on the campus late in the evening, the front garden gate was locked. As there was no one else in the building, he had to climb over the wall: »A strange move out of the Institute. Seven years ago I was proud to draw up in my carriage; now I have to leave the Institute by using this means of escape.«

A brief interlude in Berlin followed, where he completed the investigations on the effect of sodamide during condensation, which he had started in Kiel. Then he finally moved into his house in Godesberg near Bonn, which he had already purchased during his time in Kiel. He operated a private laboratory there, in which Otto Eisleb worked with him for many years, who later wrote: »It will be difficult for an outsider to believe that Claisen was particularly enthusiastic about the chemical "craft", whereas his publications were generally about important theoretical conclusions. (...) He really carried out the craft "con amore". It was moving to see how conscientious he was in approaching a new substance. (...) He then lovingly packed the compounds in attractive glass containers and put labels on them, which often contained a long description with scrupulous attention to detail on the development of the compound.« Heart and lungs had in the meantime been damaged to such an extent that Claisen even had to give up his beloved cigarettes. He died in 1930.

He was without doubt a headstrong character, which is illustrated by the reports of his contemporaries, but almost impossible to surpass in his field. His approach to work was meticulous, and he was so precise in every field that he even let one of his assistants re-write the dissertations of his students before he marked them. A thoroughness which was worthwhile, »his interpretations of discoveries all turned out to be correct«, says Schiemenz.

Jana E. Seidel

Key word: condensation reaction

Condensation plays an important role in organic chemistry: in many chemical reactions molecules interlink by separating other molecules – usually water. They "condense". In this way it is possible for enormous molecules to be created from small individual building blocks, for example fats and waxes, but also protein or starch.

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