1 and E • 2 . We believe this due to a well-known problem of DFT in describing certain radical anions of atoms and small molecules. Treating EE as a single two-electron reduction step (8) allows the radical semiquinone anion Q -to be bypassed, the accurate treatment of which calls for a higher level of theory. Overall, the good agreement between computed and experimental E • EE values provided validation of the DFT approach to study electrochemical reduction of quinones and enabled us to explore a wider range of functional group substitutions in the next section.