Under the strict application of the Cahn-Ingold-Prelog (CIP) sequence rules for assigning E/Z config — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

CIP priority is primarily determined by the atomic number of the directly attached atom. However, if the atoms are identical isotopes of the exact same element (like H, D, and T), CIP Rule 2 dictates that atomic mass acts as the definitive tie-breaker. Because Tritium ($T$, mass 3) is heavier than Deuterium ($D$, mass 2) and Hydrogen ($H$, mass 1), the priority order is strictly $-T > -D > -H$.