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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. 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 ...

  4. 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]

  5. Cyclopentadiene - Wikipedia

    en.wikipedia.org/wiki/Cyclopentadiene

    Cyclopentadiene monomer in an ice bath. Cyclopentadiene production is usually not distinguished from dicyclopentadiene since they interconvert. They are obtained from coal tar (about 10–20 g/t) and by steam cracking of naphtha (about 14 kg/t). [8]

  6. 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 ...

  7. 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 ...

  8. 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 ...

  9. Antiaromaticity - Wikipedia

    en.wikipedia.org/wiki/Antiaromaticity

    Cyclobutadiene, for example, rapidly dimerizes with no potential energy barrier via a 2 + 2 cycloaddition reaction to form tricyclooctadiene. [14] While the antiaromatic character of cyclobutadiene is the subject of debate, the relief of antiaromaticity is usually invoked as the driving force of this reaction. Dimerization of cyclobutadiene