Primary isotope effect

{
  "id": "MLC-T-CHM-009431",
  "term": "Primary isotope effect",
  "field": "Chemistry",
  "definition": "The change in reaction rate or equilibrium constant when an atom directly involved in the bond-breaking or bond-forming step of a reaction is replaced by one of its isotopes. This effect arises from the difference in vibrational frequencies of the isotopic bonds, which affects the zero-point energy. It is typically observed when hydrogen is replaced by deuterium or tritium.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "equilibrium constant",
    "isotope effect",
    "kinetic isotope effect",
    "pre-equilibrium",
    "rate-controlling step",
    "secondary isotope effect"
  ],
  "references": [
    "PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1130 (https://doi.org/10.1351/pac199466051077)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/primary-isotope-effect/"
}