antiaromatic

antiaromatic

[‚an·tē‚ar·ə′mad·ik]
(chemistry)
A cyclic compound with delocalized electrons that does not obey Hückel's rule, and is much less stable than similar nonaromatic compounds.
References in periodicals archive ?
Aromatic systems have pretty negative NICS values, antiaromatic systems have strongly positive NICS values, and nonaromatic cyclic systems should have NICS values close to zero [35,42-44].
When the value of the HOMA index is less than zero, the structure is antiaromatic.
They're classified as antiaromatic molecules, which chemical theory predicts will be extremely reactive--in contrast to aromatics, such as benzene, which have unusually stable structures.
The cyclopentadienyl cation is a common textbook example of an antiaromatic molecule, a molecule so electronically unstable and, therefore, extremely reactive that it should not exist for any length of time.