Question - (4) - The 3-substituted 3-amino oxindole is synthesized starting from ketimines derived from isatin. After close examination, it is observed that the final product is in the racemic form. How to find out exact percentage of the individual isomer in this racemic mixture?
Answer -
By HPLC method - Use HPLC with a chiral column for separation and area normalization for % isomers.
By NMR method - If you want to avoid chiral HPLC Column separation, you may try using a chiral shift reagent and get the ratio in NMR. If your enantiomers resolve, you can easily get the percent ratio.