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Unlike aromatic compounds, which follow Hückel's rule ([4n+2] π electrons) [1] and are highly stable, antiaromatic compounds are highly unstable and highly reactive. To avoid the instability of antiaromaticity, molecules may change shape, becoming non-planar and therefore breaking some of the π interactions.
Benzo[c]phenanthrene is a polycyclic aromatic hydrocarbon with the chemical formula C 18 H 12. It is a white solid that is soluble in nonpolar organic solvents. It is a nonplanar molecule [1] [2] consisting of the fusion of four fused benzene rings. The compound is of mainly theoretical interest but it is environmentally occurring [3] and ...
Annulenes may be aromatic (benzene, [6]annulene and [18]annulene), non-aromatic ([8] and [10]annulene), or anti-aromatic (cyclobutadiene, [4]annulene). Cyclobutadiene is the only annulene with considerable antiaromaticity, since planarity is unavoidable.
The barrier to being non-planar is very low at 0.6 kcal/mol, so at standard conditions the ring is on average flat. [1] Unlike aromatic compounds, it has alternating bond lengths in the rings. One double bond is in the exclusive part of the four member ring (from carbon 9 to 10) and four double bonds are in the eight-member ring, at positions 1 ...
Aromatic properties have been attributed to non-benzenoid compounds such as tropone. Aromatic properties are tested to the limit in a class of compounds called cyclophanes. A special case of aromaticity is found in homoaromaticity where conjugation is interrupted by a single sp³ hybridized carbon atom.
It is an unstable, non-planar compound which is non-aromatic. [1] [2] The dianion, however, satisfies Hückel's rule, is thermally stable, and is planar. [3] See also
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 ...
This organic compound is a conjugated 10 pi electron cyclic system and according to Huckel's rule it should display aromaticity. It is not aromatic, however, because various types of ring strain destabilize an all-planar geometry. [1]: 121–122