For part B, I think you\'re essentially creating diastereomers by forming an add
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For part B, I think you're essentially creating diastereomers by forming an adduct. They two molecules interact so strongly that it'll behave as a single molecule with two chiral centers. Is that it? Thanks in advance!
4. Answer questions a)-c) based on the figures provided below. a) Jason, a CHEM 30CL student, takes an 'H NMR of an R/S mixture of naproxen. Figure 1 shows the partial 'H NMR spectrum. He finds that he cannot figure out the R/S ratio based on this spectrum. Why? Fiqure 1 7.15 7.10 6.96 6.80 675 b) Jason adds quinine, a chiral solvating agent (CSA), to the RAS naproxen mixture. Quinine contains a basic tertiary amine moiety, which forms an acid-base adduct with the carboxylic acid group on naproxen. He takes the 'H NMR again, and sees two sets of signals this time in a 1:2 ratio. Why are the R and S enantiomers of naproxen now distinguishable by H NMR? Figure 2 -58 quinine 7.15 7.10 7.05 7.00 6.90 6 75Explanation / Answer
Answer:
a) We can not distinguish R & S isomers differ in the optical rotations , however they give rise to same PMR spectrum with the overlapping of the signals.Therefore ,R & S isomers cannot be distinguished by PMR.
b) When quinine is added to the mixture of R & S isomers the separation can be achieved as the pure enantiomer of chiral auxillary compound quinine forms a separable diastereoisomeric adducts . Hence , one gets separate sets of signals in PMR. Cleavage of the chiral auxillary separates two diastereoisomers of naproxen . By cleavage of chiral auxiliary frees both enantiomers of the recemates.
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