Typically, this would lead researchers to conclude that the
two structurally similar compounds have opposite absolute
configuration. On the contrary, the reaction proceeds with
retention of configuration as expected. A published study of the
single crystal CD spectroscopy on [Λ-Co(en)3]Cl3·NaCl·6H2O
allows students to understand why the CD spectra show
opposite sign of the rotation of polarized light for the same
absolute configuration at the metal center.12 A discussion of the
argument is presented in our Supporting Information. The
equations for calculation of enantiomeric excess from the
intensity of the CD signal at a given wavelength13 relative to
published literature values for samples of known optically pure
Λ-Co(en)3
3+ and Λ-Co(diNOsar)3+ products14 can also be
found in our Supporting Information.