2022 is a more appropriate year than 2015 to celebrate the 150th anniversary of the Kekulé benzene structure, for in 1865 Kekulé did not propose the familiar hexagonal 1,3,5-cyclohexatriene formulation. Why did he not?
Although the paper published by Kekulé in 1865 is generally accepted as the seminal document regarding the elucidation of the structure of benzene, it was not for another seven years that Kekulé introduced a “collision theory” which, in his view, made the 1,3,5-cyclohexatriene formulation at last acceptable. 2022 is therefore an appropriate year to celebrate the 150th anniversary of his proposal. The present Perspective focusses in particular on how Kekulé’s mind has evolved during that short period of time. After a short introduction, followed by a historical note about the emergence of aromatic chemistry and the role of Kekulé as founder of structural organic chemistry, this Perspective discloses in three chapters the step-by-step unveiling of the 1,3,5-cyclohexatriene structure and focusses on Kekulé’s own dubiety about this formula. Eventually, in 1872 Kekulé’s benzene saga is completed in the article in which he discloses his final theory on the structure of benzene. In the last section, a short review is presented on the later quest for a fully symmetric single-formula representation of benzene.Zum Volltext