ベンゼン電子式の発展
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概要
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The purpose of this study is to show why E. Huckel alone thought in the early 1930s that molecular orbital(M.O.) theory was better than valence bond(V.B.) theory. In order to elucidate it, the author has investigated the development of the electronic formula of benzene and has made clear the meaning of Huckel's quantum theoretical coutribution to the benzene problem. In the early 20th century, chemists proposed several types of the electronic formula of benzene: the ionic bond type, the tetrahedral carbon model type, the three electron bond type, the aromatic sextet type, and others. They compared these electronic formulas one another, together with the considerations of the experimental evidence. It was E. C. Crocker who first proposed the aromatic sextet type of electronic formula of benzene in 1922, although it is usually thought that R. Robinson first proposed that formula in 1925. Aromatic sextet had been recognized as one of the most reasonable structural hypothesis up to about 1930, and it was in a sense the revival of the old benzene problem, i.e., the difficulty of representation of the bonding state of benzene ring. At that time, Huckel treated the benzene problem based on wave mechamics and recognized aromatic sextet as a closed shell which was the result derived from M.O. theory but not from V.B. theory. According to Huckel, the stability of aromatic sextet should be understood as resulting from the nature of the closed shell like such of noble gas. Since Huckel could solve the benzene problem which had been unsolved for about 75 years, he thought that M.O. theory was better than V.B. theory. The author attributes rapid loss of the significance of aromatic sextet to the conflict between Robinson's and Huckel's view on, for example, induced polarities of substituted benzenes, to the critical opinion expressed by W. G. Penney, and to the imperfection of Huckel's interpretation mentioned above.
- 日本科学史学会の論文
- 1990-12-21