Archibald Scott Couper

Archibald Scott Couper

Archibald Scott Couper (born March 31, 1831 in Kirkintilloch , Scotland ; † March 11, 1892 ibid) was a Scottish chemist who established an early theory of chemical structure and bond . He developed the idea of ​​tetravalent carbon atoms joining together to form large molecules. He was convinced that the bond order of the atoms in a molecule can be determined from its chemical properties.

life and work

Couper was the only surviving son of a wealthy textile mill owner near Glasgow . He studied at the universities of Edinburgh and Glasgow and, with interruptions during the years 1851–54, also in Germany. Formally, he began studying chemistry in the fall of 1854 at the University of Berlin . In 1856 he went to the private laboratory of Charles Adolphe Wurtz at the medical faculty in Paris (today's University of Paris V ).

Couper published his "New Chemical Theory" on June 14, 1858 in compressed form in French, then in August 1858 in extensive papers in French and English. Couper developed the idea that carbon atoms to each other to connect, while rules of valence follow. He did this independently of a paper in which August Kekulé described the same concept. The thesis that carbon is tetravalent was put forward by Kekulé as early as 1857. As a result of a misunderstanding with Wurtz, Kekulé's work was the first to appear in print in May 1858, so priority as the discoverer of the self-linking of carbon went to Kekulé. When Couper angrily confronted Wurtz, Wurtz expelled him from the laboratory.

In December 1858, Couper was offered an assistantship at the University of Edinburgh. However, after his disappointment, Couper's health began to decline. In May 1859 he suffered a nervous breakdown and went to a mental institution as a private patient. When he was released in July 1859, there was a relapse almost immediately, which was explained as the result of a sunstroke. Treatment continued until November 1862. But Couper's health was now so bad that he was unable to do any serious work. He spent the last 30 years of his life in the care of his mother.

Archibald Coupers structural formulas for alcohol and oxalic acid . Element symbols stand for atoms and lines for bonds. (1858)

Couper's research differed from Kekulé's in several ways. In contrast to Kekulé, he was open to the idea of ​​a divalent carbon. In his essay he had more enlightened formulas than Kekulé. In two cases he even suggested heterocyclic formulas which Kekulé may have influenced in the later elucidation of the structure of the benzene ring . Couper assumed the atomic weight of oxygen to be 8 instead of 16, so that in Couper's formulas there are twice as many oxygen atoms as in those of Kekulé. Couper drew dotted and dashed lines between the atoms in his formulas, which comes close to the appearance of later formula drawings. In this regard, his work likely influenced the early structural theorists Alexander Michailowitsch Butlerow and Alexander Crum Brown .

Web links

• Literature by and about Archibald Scott Couper in the catalog of the German National Library