CHAPTER 5: Question 5

 

Simple Answers


Consider the reaction between an enantiomerically pure substrate [(R)-sub)] and a racemic derivatizing agent [(R)-der / (S)-der]

(R)-sub + (R)-der ------>  (R,R)-sub-der     (A)
             + (S)-der               (R,S)-sub-der     (B)

Now consider the reaction between a racemic substrate [(R)-sub / (S)-sub] and an enantiomerically pure derivatizing agent [(R)-der]

(R)-sub + (R)-der ------> (R,R)-sub-der (C)
(S)-sub                             (S,R)-sub-der (D)

Reaction A is identical to reaction C. The only difference between these two situations in in reactions B and D, for which both the starting materials and products are enantiomeric. Reactions B and D will have identical energy profiles, since the starting materials are enantiomeric (and so of equal energy), the products are enantiomeric (and so of equal energy), and any point along the reaction pathway of reaction B will be enantiomeric with the corresponding point of reaction D. Thus, if any kinetic resolution occured in reaction B, an identical kinetic resolution would be observed in reaction D.
 

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