Butalene

Butalene is a polycyclic hydrocarbon composed of two fused cyclobutadiene rings.[1] A reported possible synthesis of it involves an elimination reaction from a Dewar benzene derivative. The structure itself can be envisioned as benzene with an internal bridge, and calculations indicate it is somewhat less stable than the open 1,4-didehydrobenzene biradical, the valence isomer in which that bridged bond is broken.

Butalene
Names
IUPAC name
Bicyclo[2.2.0]hexa-1,3,5-triene
Other names
Butalene
Identifiers
3D model (JSmol)
Properties
C6H4
Molar mass 76.098 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure and bonding
Resonance is significant around the perimeter rather than through the middle.

Ab initio calculations indicate butalene has a planar geometry and, in keeping with a planar structure with 6 π-electron configuration, is aromatic. Thus, the most significant π bonding interactions involve conjugation around the periphery of the whole six-atom structure, similar to benzene, rather than cross-ring resonance along the bridging bond.[2] Significant resonance around one or the other four-membered ring alone would be a less-stable antiaromatic form, as is seen in cyclobutadiene itself.

See also

References
  1. Warner, Philip M.; Jones, Graham B. (2001). "Butalene and Related Compounds:  Aromatic or Antiaromatic?". J. Am. Chem. Soc. 123 (42): 10322–10328. doi:10.1021/ja011134v.
  2. Sakai, Shogo; Udagawa, Taro; Kita, Yuki (2009). "Theoretical Studies on the Structures and the Aromaticity for Condensed Cyclobutadienoids Series: The Combination of Kekulé Structures". J. Phys. Chem. A. 113 (50): 13964–13971. doi:10.1021/jp906258e.
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