Σ-adduct

{
  "id": "MLC-T-CHM-010475",
  "term": "Σ-adduct",
  "field": "Chemistry",
  "definition": "A species formed by the addition of an electrophile or nucleophile to a carbon atom of an aromatic or unsaturated system, resulting in the formation of a new sigma (σ) bond. This addition disrupts the aromaticity or pi system temporarily, creating an intermediate with a localized charge. These adducts, also known as Meisenheimer complexes in some cases, are key intermediates in nucleophilic and electrophilic aromatic substitution reactions.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "Meisenheimer adduct",
    "adduct",
    "attachment",
    "conjugated system",
    "electrophilicity",
    "entering group",
    "nucleophilicity",
    "radical"
  ],
  "references": [
    "PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1170 (https://doi.org/10.1351/pac199466051077)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/s-adduct/"
}