Friedrich August Kekulé

(full name, Friedrich August Kekulé von Stradonitz). Born Sept. 7, 1829, in Darmstadt; died July 13, 1896, in Bonn. German organic chemist; assistant professor at the University of Heidelberg from 1856 to 1858, then professor of chemistry at the University of Ghent (Belgium). Became professor of chemistry at the University of Bonn in 1865 and president of the German Chemical Association in 1886. In 1854 he produced thioacetic acid, and in 1856, glycolic acid. In 1872 he collaborated with the Dutch chemist A. Fransimon (1844–1919) to produce triphenylmethane and anthraquinone.

Kekulé’s main works were devoted to theoretical chemistry. In 1854 he first formulated the concept of the dibasicity (that is, diatomicity or bivalency) of sulfur and oxygen; in 1857 he divided the elements into unibasic, dibasic, and tribasic. Together with the German chemist Kolbe, Kekulé defined carbon as a tetratomic element. In 1858 he demonstrated the ability of carbon atoms to combine with one another (the Scottish chemist A. Couper undertook the same task). In the following years, Kekulé developed the theory of polyatomic radicals. In 1865 he proposed the cyclic formula for the structure of benzene, with alternating single and double bonds; at the same time he expanded Butlerov’s theory on the chemical structure of aromatic compounds. Kekulé explained the structure of azo and diazo compounds.