b) The two enantiomers of the unabsorbed compound will be of equal energy, as will the two enantiomers of the absorbed compound, since the chromatography column is achiral. Further, since enantiomers have identical chemical and physical properties in the absence of other chiral species, the transition states for the absorption will also be of equal energy, as will all points on the absorption / energy diagram as shown below. Thus the two enantiomers of the compound will be absorbed onto the column at the same rate, and with the same free energy of absorption. Hence, the chromatography column will not separate the two enantiomers of the compound.
c) The two enantiomers of the unabsorbed compound will be of equal energy,
however, since the chromatography column is chiral, the two enantiomers
of the absorbed compound will have different energies, and the transition
states for absorption will also be different. Hence, the two compounds
will be absorbed onto
the chromatography column at different rates and will be absorbed with
different binding strengths (ie with different free energies of absorption)
as shown below. The enantiomer which is absorbed least strongly will be
the first to be eluted from the chromatography column.
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