Cyclobutadiene Antiaromaticity

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cyclobutadiene


however, has long been questioned if cyclobutadiene genuinely antiaromatic , recent discoveries have suggested may not be. cyclobutadiene particularly destabilized , attributed antiaromaticity. however, cyclobutadiene adopts more double bond character in 2 of parallel bonds others , π electrons not delocalized between 2 double-bond-like bonds, giving rectangular shape opposed regular square. behaving 2 discrete alkenes joined 2 single bonds, , therefore non-aromatic rather antiaromatic.


despite lack of π-antiaromatic destabilization effect, none of 4n π-electron relatives (cyclooctatetraene, etc.) had close destabilization, suggesting there more going on in case of cyclobutadiene. found combination of angle strain, torsional strain, , pauli repulsion leads extreme destabilization experienced in molecule.


this discovery awkward in contradicts basic teachings of antiaromaticity. @ point of time, presumed cyclobutadiene continue used introduce concept of antiaromaticity in textbooks matter of convenience, though classifying antiaromatic technically may not accurate.








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