Claus' benzene explained

Claus' benzene (C₆H₆) is a hypothetical hydrocarbon and an isomer of benzene.^[1] It was proposed by Adolf Karl Ludwig Claus in 1867^[2] as a possible structure for benzene at a time when the structure of benzene was still being debated. The molecule can be described as a hexagon with carbon atoms positioned at the corners, with each carbon connected to its two ortho carbons (the nearest carbons) and the one para carbon connected diametrically.^[3] High strain energy makes its synthesis impossible. Although it is often referred to alongside Dewar benzene and prismane, it is not possible to synthesise it, while Dewar benzene and prismane can be.^[4]

Notes and References

1. Organic Reactions And Their Mechanisms P. S. Kalsi 2000
2. Claus, Adolph K. L. (1867) "Theoretische Betrachtungen und deren Anwendungen zur Systematik der organischen Chemie" (Theoretical considerations and their applications to the classification scheme of organic chemistry), Berichte über die Verhandlungen der Naturforschenden Gesellschaft zu Freiburg im Breisgau (Reports of the Proceedings of the Scientific Society of Freiburg in Breisgau), 4: 116–381. In the section Aromatischen Verbindungen (aromatic compounds), p. 315–347, Claus presents Kekulé's hypothetical structure for benzene (p. 317), presents objections to it, presents an alternative geometry (p. 320), and concludes that his alternative is correct (p. 326). See also figures on p. 354 or p. 379.
3. 10.1021/ja00039a058. Valence isomers of benzene and their relationship to isomers of isoelectronic P6. 1992. Warren . D. S.. Gimarc . B. M.. Journal of the American Chemical Society. 114. 13. 5378 .
4. 10.1002/anie.200705775. 18418829. 2008. Hoffmann . R.. Hopf . H.. Learning from molecules in distress. 47. 24. 4474–4481. Angewandte Chemie International Edition in English .