Two electrochemical oxidation waves assigned to the D5h isomer of Sc3N@C80 have beenidentified, and a 270-mV difference in the first electrochemical oxidation potentials of the Ih and D5h isomershas been measured. On the basis of this oxidative potential difference, a strategy for isomeric purificationinvolving a selective chemical oxidation of the D5h isomer is reported. Variable scan cyclic voltammetry ofthe resultingly pure Sc3N@C80Ih isomer shows evidence of a rapid endohedral chemical reaction followingthe first reduction process.