August Kekule

August Kekule was a German organic chemist who proposed that carbon atoms are tetravalent and bond to one another in chains, work that let chemists reason systematically about the structure of organic molecules for the first time. In 1865 he proposed that benzene, whose composition had long puzzled chemists, is a ring of six carbon atoms rather than a chain, resolving a structural problem that had resisted explanation for years. At a celebration in Berlin on 11 March 1890 marking the twenty-fifth anniversary of that proposal, Kekule told the audience the ring structure had come to him in a reverie of a snake seizing its own tail. The benzene ring itself is not in question, but historians of science treat the snake story with caution as a retrospective anecdote told twenty-five years after the fact for a commemorative occasion, with no contemporary record from 1865 to support it; some historians argue the story was shaped for its audience rather than recalled as a literal memory.