Benzene: Introduction to Aromatic Compounds
Structure of Benzene
Even though Michael Faraday had already discovered benzene and Eilhardt Mitscherlich had determined its empirical formula, the structure of benzene remained a riddle. Several possible structures were taken into account. Two of these structures were named after the scientists by whom they were proposed: Dewar benzene (after James Dewar) and Ladenburg benzene (after Albert Ladenburg). Two such other proposals for the benzene structure were benzvalene and 3,3'-bicyclopropenyl. The latter one was actually synthesized by W.E. Billups et al. in 1989.
The German chemist August Kekulé von Stradonitz then proposed a monocyclic structure of benzene, containing three cyclically conjugated double bonds. Systematically, this structure would be called 1,3,5-cyclohexatriene. As legend has it, Kekulé came up with the idea of this structure in a dream of snakes. Each of the snakes bit into the tail of another snake. As a result, the snakes depicted a cyclic structure.
Later, the so-called Kekulé formula was generally accepted. In 1861, even four years before Kekulé's proposal, the Austrian teacher Joseph Loschmidt had also published a similar benzene structure.