Hückel, Erich Armand Arthur Joseph (1896-1980)

German physical chemist who, with Peter Debye, developed in 1923 the modern theory that accounts for the electrochemical behaviour of strong electrolytes in solution. Hückel also made discoveries relating to the structures of benzene and similar compounds that exhibit aromaticity (see aromatic compound).

Hückel was born in Berlin and studied at Göttingen. He worked with Debye at Göttingen and the Eidgenössische Technische Hochschule, Zürich, and held various academic posts, becoming professor of theoretical physics at the University of Marburg 1937.

In 1930, Hückel began his work on aromaticity, the basis of the chemical behaviour of benzene, pyridine, and similar compounds. He developed a mathematical approximation for the evaluation of certain integrals in the calculations concerned with the exact nature of the bonding in benzene. Extending his research to other, similar chemical systems, he formulated the Hückel rule for monocyclic systems, which states that for aromaticity to occur the number of electrons contributing to the correct type of bonding (π-bonding) must be 4n + 2, where n is a whole number. In large ring systems, however, the predicted aromaticity does not occur.