Element effect

{
  "id": "MLC-T-CHM-003801",
  "term": "Element effect",
  "field": "Chemistry",
  "definition": "A comparison of reaction rates in which only the leaving-group atom is changed to a different element, usually expressed as a quotient such as kBr/kCl. A value near 1 shows that departure of the leaving group is not part of the rate-determining step, whereas a large value shows that breaking of the bond to that atom is. In nucleophilic aromatic substitution, fluoride leaving faster than chloride is the classic sign of an addition-first mechanism.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "isotope effect",
    "leaving group"
  ],
  "references": [
    "PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1111 (https://doi.org/10.1351/pac199466051077)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/element-effect/"
}