Para-Bond or "Dewar" Benzene? Wilson Baker and Dennis H. Rouvray Department of Organic Chemistry The University Bristol, England and Institut f u r Strahlenchemie im Max-Planck-Znstitut fur Kohlenforschung Miilheim a n der Ruhr, Germany The preparation of bicyclo[2.2.0]hexa-2,5-dienesome 15 years ago ( I ) was hailed as the first complete synthesis of the simplest member of a new class of unsaturated hydrocarbons which for long had been termed "Dewar benzenes." This unfortunate naming arose from an almost incredible misreading of Sir James Dewar's paper of 1867 in the Proceedings of the Royal Society of Edinburgh (2). Few, if any, of the countless chemists who have since used the term "Dewar henzene" could ever have read this important communication, for it is almost universally thought that Dewar proposed a new structure for the henzene molecule in opposition to that postulated by KekulC. a year or so earlier (3).The two structures in question are depicted below
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Kekuli. Structure
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So-called Dewar Structure
A study of Dewar's Paper, however, reveals beyond any possibility of doubt that it was never Dewar's intention to do this, and as a consequence the name "Dewar henzene" is a misnomer and should therefore he dropped. A great chemist should not be forever dishonored by attributing to him a structure for benzene which he had not proposed and which was, to make matters worse, incorrect. The contributions of Dewar (1842-1923) to physics and chemistry have been manifold (4). Although primarily an organic chemist he investigated among other things several metal carhonyls, a method of preparing active charcoal, the formulas to he assigned to various organic species including that for pyridine, the use of spectroscopy for the study of oreanic structure. and he was also the inventor of the propellant explosive cordite. In 1884 he turned his attentions& thk study of low temperature phenomena and, in the course of the latter, invented
