https://doi.org/10.1351/goldbook.A05436
The product formed by the @[email protected] of an @[email protected] or @[email protected] @[email protected] or of a @[email protected] to a ring carbon of an aromatic species so that a new σ-bond is formed and the original @[email protected] is disrupted. (This has generally been called a 'σ-complex', but @[email protected] is more appropriate than complex according to the definitions given.) The term may also be used for analogous adducts to unsaturated (and conjugated) systems in general.
See also:
Meisenheimer adduct
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1170 [Terms] [Paper]