Cyclobutadien: der Inbegriff eines antiaromatischen Moleküls?

Abstract

Die Bildungsenthalpie von Cyclobutadien wurde jüngst durch Kass et al. bestimmt, was zum Anlass für einige Betrachtungen über die Schwierigkeit genommen wird, aus diesem Wert die „antiaromatische Destabilisierungsenergie“ und die Spannungsenergie dieser wichtigen Spezies abzuleiten.

Synthesis, Structure, and Reactivity of Lewis Base Stabilized Plumbacyclopentadienylidenes

“…[5] On the other hand, antiaromaticity, which was first introduced in 1965, [6] is used to explain peculiar instability of the cyclic conjugated compounds with 4n p electrons, [7] and even all-metal antiaromaticity has recently been proposed. [1l, 8] However, the question of whether antiaromaticity of compounds with heavier Group 14 atoms in the p-frameworks is maintained remains elusive, even though a few analogues of cyclobutadiene containing heavier Group 14 atoms have already been synthesized.…”

An Extensive n, π, σ‐Electron Delocalized Si4 Ring

“…[1] Its existence in solution is shown by various trapping reactions to form Diels-Alder adducts. One of the well-studied examples is cyclobutadiene, which is the smallest annulene containing conjugated double bonds (4p electrons).…”

“…One of the well-studied examples is cyclobutadiene, which is the smallest annulene containing conjugated double bonds (4p electrons). [1] Its existence in solution is shown by various trapping reactions to form Diels-Alder adducts. [2] Moreover, cyclobutadiene derivatives that are stable at room temperature, in which the carbon atoms are incorporated with sterically hindered substituents, have been synthesized and structurally characterized.…”