Question

Can you use proton NMR and polarimetry to determine wither a chiral molecule with one chiral center is (r) or (s) enantiomer?

Answer 1

Chiral center is present in enantiomers (One chiral center) as well as diastereomers (More than one chiral center). Proton NMR will distinguish between diastereomers and not enantiomers. Because enantiomers are beheving similarly in achiral medium. Hence it can not be differentiated. But diastereomers can be differentiated between in proton NMR since they are chemically different.

Polarimetry can be used determine whether it is a chiral molecule or not. Because achiral molecules will be zero rotation in polarimetry and chiral molecules will be having postive or negative value but not zero.