Preferred Label : antiaromaticity;
Detailed label : antiaromaticity (antithetical to aromaticity);
IUPAC definition : Those cyclic molecules for which cyclic electron delocalization provides for the reduction
(in some cases, loss) of thermodynamic stability compared to acyclic structural analogues
are classified as antiaromatic species. In contrast to aromatic compounds, antiaromatic
ones are prone to reactions causing changes in their structural type, and display
tendency to alternation of bond lengths and fluxional behavior (see fluxional molecules)
both in solution and in the solid. Antiaromatic molecules possess negative (or very
low positive) values of resonance energy and a small energy gap between their highest
occupied and lowest unoccupied molecular orbitals. In antiaromatic molecules, an external
magnetic field induces a paramagnetic electron current. Whereas benzene represents
the prototypical aromatic compound, cyclobuta-1,3-diene exemplifies the compound with
most clearly defined antiaromatic properties.;
Origin ID : AT06987;
See also
Those cyclic molecules for which cyclic electron delocalization provides for the reduction
(in some cases, loss) of thermodynamic stability compared to acyclic structural analogues
are classified as antiaromatic species. In contrast to aromatic compounds, antiaromatic
ones are prone to reactions causing changes in their structural type, and display
tendency to alternation of bond lengths and fluxional behavior (see fluxional molecules)
both in solution and in the solid. Antiaromatic molecules possess negative (or very
low positive) values of resonance energy and a small energy gap between their highest
occupied and lowest unoccupied molecular orbitals. In antiaromatic molecules, an external
magnetic field induces a paramagnetic electron current. Whereas benzene represents
the prototypical aromatic compound, cyclobuta-1,3-diene exemplifies the compound with
most clearly defined antiaromatic properties.
