3D model (JSmol)
|Molar mass||182.266 g·mol���1|
|Solubility in benzene||Soluble|
|Main hazards||Flammable, reactive|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Cyclotetradecaheptaene, often referred to as annulene, is a hydrocarbon with molecular formula C14H14, which played an important role in the development of criteria (Hückel's rule) for the aromaticity, a stabilizing property of central importance in physical organic chemistry. Although the conjugated ring of this annulene contains 4n+2 electrons, it only exhibits limited evidence for being aromatic. It does not fully conform to Hückel's rule because none of its cis/trans isomers can adopt a completely planar conformation due to crowding of the interior hydrogens. There is evidence that it has two isomeric forms of comparable stability (trans, cis, trans, cis, trans, trans, cis- with four interior hydrogens (shown in the infobox) and trans, cis, trans, cis, trans, cis, cis- with three interior hydrogens) which rapidly interconvert at room temperature but can be observed at low temperature by NMR. Its 1H NMR spectrum shows evidence of aromatic ring currents that result in an upfield shift for the interior hydrogens. In contrast, the corresponding - and annulenes, which are weakly antiaromatic or nonaromatic, have downfield shifted interior hydrogens. However, unlike the undoubtedly aromatic annulene, annulene does not bear the hallmark aromatic property of chemical stability, and it quickly decomposes when exposed to light and air.
- G. M. Badger. Aromatic Character and Aromaticity. Cambridge University Press. p. 96.
- H., Lowry, Thomas (1987). Mechanism and theory in organic chemistry. Richardson, Kathleen Schueller. (3rd ed.). New York: Harper & Row. ISBN 0060440848. OCLC 14214254.
- Sondheimer, Franz; Gaoni, Yehiel (1960). "Unsaturated Macrocyclic Compounds. XV. Cyclotetradecaheptaene". Journal of the American Chemical Society. 82 (21): 5765–5766. doi:10.1021/ja01506a061.
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