Chloroquine and hydroxychloroquine have an stereogenic sp 3 carbon atom in a central location of the molecules (Figure ). It is unclear in our survey of the literature if it is known which stereoisomer is the preferentially active one, or if both are. Consequently, both stereoisomers were investigated, with B97-D3(BJ)/cc-pVTZ identifying over 100 unique stationary points for each isomer whose relative energies range up to 16.5 kcal•mol -1 (Tables and). Only three and two conformations of chloroquine isomers 1 and 2 possessed relative energies below 2.0 kcal•mol -1 .