https://doi.org/10.1351/goldbook.A00441
- In the traditional sense, 'having a chemistry typified by benzene'.
- A cyclically conjugated molecular entitywith a stability (due todelocalization) significantly greater than that of a hypothetical localized structure (e.g.Kekulé structure) is said to possess aromatic character. If the structure is of higher energy (lessstable) than such a hypothetical classical structure, the molecular entity is 'antiaromatic'. The most widely used method for determiningaromaticityis the observation of diatropicity in the 1HNMR spectrum.See also:Hückel (4n + 2) rule,Möbius aromaticity
- The terms aromatic and antiaromatic have been extended to describe the stabilization or destabilization of transition statesofpericyclic reactions. The hypothetical reference structure is here less clearly defined, and use of the term is based on application of theHückel (4n + 2) ruleand on consideration of the topology of orbital overlap in thetransition states. Reactions of molecules in theground stateinvolving antiaromatic transition states proceed, if at all, much less easily than those involving aromatic transition states.