The formula of benzene offered difficulty if the quadrivalence of carbon was to be maintained, and the same difficulty was encountered with other compounds, which, since they often possess aromatic odors, were called "aromatic compounds" by Kekulé. The correct structure of benzene was first given by Kekulé in a paper communicated to the Paris Chemical Society in 1865. In it, he says that "in all aromatic compounds . . . contain a common nucleus composed of six carbon atoms. Six carbon atoms [can] form an open chain . . . If the further assumption is made that the two carbon atoms which terminate the chain are bound to one another, a closed chain is obtained." The idea for the benzene formula was stated by Kekulé to have arisen in his famous dream, in which chains of carbon atoms were like snakes, twisting and curling until one gripped its own tail. Kekulé subsequently spent many years working on the structure on benzene and other aromatic substances, attempting to prove experimentally the reality of the flat or planar ring structure and the presence in the ring of three alternating double bonds. "All the research on aromatic compounds following the introduction of the ring formula proved to be consistent with the concept of a planar rather that a three-dimensional molecule . . . organic chemists found the Kekulé formula a satisfactory working concept; hence the chemistry of aromatic compounds advanced rapidly during the final three decades of the last [nineteenth] century."
Norman Library of Science, 1205;.Partington IV, p553-554.
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