Question

7) A solution of an enantiomerically pure sample of (R)- 3-chloropentanoic acid is made by dissolving 2.5 g of the compound in 100 mL of water. a. Calculate the specific rotation of (R)- 3-chloropentanoic acid if the observed rotation of the above sample is +2.78° when measured in a 40 cm tube. g/mL +2.7% = 127.5 10025(4) b. What is the specific rotation of (S)-3-chloropentanoic acid? -27,8 c. A chemist prepares a sample which is a mixture of both enantiomers of 3-chloropentanoic acid. The sample has a specific rotation of +12.7º. Which enantiomer is present in the higher concentration? d. What is the % e.e. of the sample? (217 278 e. What % of the sample is the R enantiomer? f. What % of the sample is the Senantiomer?

Answer 1

pecific notaton f (R)-3- thloro hotahon of Soln Calculate the peidanoie auid th obsenved above saup is +2.78* when mearued in a 4oun tube the Fonmula ved dobs Specific hotanon f obsehved hotab' on Sxeri mentaly con clnthaton in /ml Соbs tub e used in dm (ioun) path lauth Hera +2-78 dobi 25 17 C = o.02S 40 4dm +2-78 o. o25X4 « +27.8 Specific notahon )-3-chlotopentanoic a cio will be 27.0 reverse are Because R aund S еach онeя. R-3-chloropenteuoíe acid +27.0 -3-chloropeutanoie acid -27.8

P Presaut in tne R, eutuntiomer higher cancentrahion because + is stand yoh R in the 2ues hon will be fo K- euantiomes with (d) e.e. xloo +2.78 ylD +27. 8 Le) R+ Sloo/ e.e. R-S fhom eguation a' aud i) we 2R 1o the R enantromes 55 thauple the saumplo S enautiomes the