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  2. 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.

  3. Möbius aromaticity - Wikipedia

    en.wikipedia.org/wiki/Möbius_aromaticity

    In contrast to the rarity of Möbius aromatic ground state molecular systems, there are many examples of pericyclic transition states that exhibit Möbius aromaticity. The classification of a pericyclic transition state as either Möbius or Hückel topology determines whether 4N or 4N + 2 electrons are required to make the transition state aromatic or antiaromatic, and therefore, allowed or ...

  4. Aromaticity - Wikipedia

    en.wikipedia.org/wiki/Aromaticity

    Molecules that could be antiaromatic will tend to alter their electronic or conformational structure to avoid this situation, thereby becoming non-aromatic. For example, cyclooctatetraene (COT) distorts itself out of planarity, breaking π overlap between adjacent double bonds.

  5. Baird's rule - Wikipedia

    en.wikipedia.org/wiki/Baird's_rule

    The lowest triplet state of an annulene is, according to Baird's rule, aromatic when it has 4n π-electrons and antiaromatic when the π-electron count is 4n + 2, where n is any positive integer. This trend is opposite to that predicted by Hückel's rule for the ground state, which is usually the lowest singlet state (S 0).

  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. Aromatic compound - Wikipedia

    en.wikipedia.org/wiki/Aromatic_compound

    Heteroarenes are aromatic compounds, where at least one methine or vinylene (-C= or -CH=CH-) group is replaced by a heteroatom: oxygen, nitrogen, or sulfur. [3] Examples of non-benzene compounds with aromatic properties are furan, a heterocyclic compound with a five-membered ring that includes a single oxygen atom, and pyridine, a heterocyclic compound with a six-membered ring containing one ...

  8. Category:Aromatic compounds - Wikipedia

    en.wikipedia.org/wiki/Category:Aromatic_compounds

    Aromatic compounds, also known as arenes or aromatics, are chemical compounds that contain conjugated planar ring systems with delocalized pi electron clouds instead of discrete alternating single and double bonds. Typical aromatic compounds are benzene and toluene. They should satisfy Hückel's rule.

  9. Aliphatic compound - Wikipedia

    en.wikipedia.org/wiki/Aliphatic_compound

    Acyclic aliphatic/non-aromatic compound Cyclic aliphatic/non-aromatic compound (cyclobutane)In organic chemistry, hydrocarbons (compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (/ ˌ æ l ɪ ˈ f æ t ɪ k /; G. aleiphar, fat, oil).