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 ?
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.
It was thought that the cyclopentadienyl cation ought to be antiaromatic and hence unstable, because its electronic configuration corresponds to that predicted by theory to be antiaromatic.