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  2. Cyclobutadiene - Wikipedia

    en.wikipedia.org/wiki/Cyclobutadiene

    The rectangular structure is consistent with the existence of two different 1,2-dideutero-1,3-cyclobutadiene valence isomers. This distortion indicates that the pi electrons are localized, in agreement with Hückel's rule which predicts that a π-system of 4 electrons is not aromatic. In principle, another situation is possible.

  3. Butalene - Wikipedia

    en.wikipedia.org/wiki/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 ...

  4. Cyclobutene - Wikipedia

    en.wikipedia.org/wiki/Cyclobutene

    The compound was first prepared by thermolysis of the ammonium salt [C 4 H 7 N(CH 3) 3]OH (cyclobutyltrimethylammonium hydroxide). [2] Cyclobutene thermally isomerizes to 1,3-butadiene. This strongly exothermic reaction reflects the dominance of ring strain. In contrast, the corresponding equilibrium for hexafluorocyclobutene disfavors ...

  5. Hückel's rule - Wikipedia

    en.wikipedia.org/wiki/Hückel's_rule

    Cyclooctatetraene (C 8 H 8) with eight π electrons has a nonplanar "tub" structure. However the dianion C 8 H 2– 8 (cyclooctatetraenide anion), with ten π electrons obeys the 4n + 2 rule for n = 2 and is planar, while the 1,4-dimethyl derivative of the dication, with six π electrons, is also believed to be planar and aromatic. [8]

  6. Antiaromaticity - Wikipedia

    en.wikipedia.org/wiki/Antiaromaticity

    For example, the aromatic species 1 can be reduced to 2 with a relatively small penalty for forming an antiaromatic system. The antiaromatic 2 does revert to the aromatic species 1 over time by reacting with oxygen in the air because the aromaticity is preferred. [15] The loss of antiaromaticity can sometimes be the driving force of a reaction.

  7. Benzocyclobutadiene - Wikipedia

    en.wikipedia.org/wiki/Benzocyclobutadiene

    Benzocyclobutadiene is the simplest polycyclic hydrocarbon, being composed of an aromatic benzene ring fused to an anti-aromatic cyclobutadiene ring. It has chemical formula C 8 H 6 . Though the benzene ring is stabilized by aromaticity , the cyclobutadiene portion has a destabilizing effect.

  8. Homoaromaticity - Wikipedia

    en.wikipedia.org/wiki/Homoaromaticity

    Homoaromaticity, in organic chemistry, refers to a special case of aromaticity in which conjugation is interrupted by a single sp 3 hybridized carbon atom. Although this sp 3 center disrupts the continuous overlap of p-orbitals, traditionally thought to be a requirement for aromaticity, considerable thermodynamic stability and many of the spectroscopic, magnetic, and chemical properties ...

  9. Annulene - Wikipedia

    en.wikipedia.org/wiki/Annulene

    Using this form of nomenclature 1,3,5,7-cyclooctatetraene is [8]annulene and benzene is [6]annulene (and occasionally referred to as just 'annulene'). [ 2 ] [ 3 ] The discovery that [18]annulene possesses a number of key properties associated with other aromatic molecules was an important development in the understanding of aromaticity as a ...