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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 .

  3. 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]

  4. Butadiene - Wikipedia

    en.wikipedia.org/wiki/Butadiene

    1,3-Butadiene (/ ˌ b juː t ə ˈ d aɪ iː n / ⓘ) [8] is the organic compound with the formula CH 2 =CH-CH=CH 2. It is a colorless gas that is easily condensed to a liquid. It is a colorless gas that is easily condensed to a liquid.

  5. 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 ...

  6. Aromaticity - Wikipedia

    en.wikipedia.org/wiki/Aromaticity

    Whereas benzene is aromatic (6 electrons, from 3 double bonds), cyclobutadiene is not, since the number of π delocalized electrons is 4, which of course is a multiple of 4. The cyclobutadienide (2−) ion, however, is aromatic (6 electrons).

  7. Heterocyclic compound - Wikipedia

    en.wikipedia.org/wiki/Heterocyclic_compound

    A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). [1] Heterocyclic organic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of organic heterocycles .

  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 ...