CHAPTER 5 HW: STEREOISOMERS

Transcription

1 CAPTER 5 W: STEREISMERS CIRALITY AND ENANTIMERS 1. Define the following terms: a. Chiral b. Enantiomers (and give an example) 2. Put an asterisk (*) on all chiral centers in these compounds. Some may have no chiral centers and some may have more than one. F 3. Find the chiral center in each compound, then draw both enantiomers. a. b. 4. Draw the enantiomer of each compound. Compound Enantiomer Compound Enantiomer F C 3 Page 1

2 DIASTEREMERS AND MES CMPUNDS 5. Define the following terms and give an example of each: a. Diastereomers b. Meso compound 6. Draw a diastereomer of each compound. Compound A diastereomer Compound A diastereomer C 3 C 3 7. Draw two stereoisomers of the structure below that are diastereomers of each other. 8. Draw a compound with a molecular formula of C that is A chiral compound. A meso compound. An achiral compound that is not a meso compound. A constitutional isomer of your previous structure. Page 2

3 9. Identify the relationship between each pair of compounds. Are they identical, constitutional isomers, enantiomers, diastereomers, or not isomers? C 2 C 3 C 2 C 3 C 2 C 3 C 2 C A meso compound has no enantiomer, but can have a diastereomer. Explain and give examples. 11. Explain why compound M has no enantiomer and why compound N has no diastereomer. C 2 C 2 C 2 C 3 M N 12. For n chiral centers in a compound, there may be 2 n possible stereoisomers. 2,4-dichloropentane has two chiral centers, but only has three stereoisomers. Explain why this is, using structures. Page 3

4 R,S DESIGNATINS 13. Circle the four different groups around each chiral center, then rank each group from 1-4 using priorities for R,S nomenclature. 14. Determine the R,S configuration of each chiral center. 3 C a. b. C C c. C 3 d. e. N 2 S 15. Ketamine is an anesthetic used in human and veterinary medicine. It is also used by some recreationally as a club drug. It is often administered as a racemic mixture, although the more active form is the S enantiomer. Which of the structures below is (S)-ketamine? NC 3 NC Why is cis-1-chloro-2-methylcyclopentane an incomplete name for this structure? C 3 Page 4

5 17. Give the IUPAC name for each compound, including R,S designations. Structure Name Structure C 2 C 3 C 3 F Name 18. Draw the structure from the following names, including dashed and wedged bonds where appropriate. Structure Name (R)-3-methylhexane (3S,6R)-6-isopropyl-3-methyldecane 19. Multiple choice: choose the best answer(s). a. The enantiomer of (2S,3S)-3-bromo-2-chloropentane is: (2S,3R)-3-bromo-2-chloropentane (2R,3R)-3-bromo-2-chloropentane (2R,3S)-3-bromo-2-chloropentane b. The following are diastereomers of (1R,3S)-1-ethyl-3-methylcyclohexane: (1R,3R)-1-ethyl-3-methylcyclohexane (1S,3R)-1-ethyl-3-methylcyclohexane (1S,3S)-1-ethyl-3-methylcyclohexane Page 5

6 FISCER PRJECTINS 20. Draw the following: Draw the enantiomer Draw a diastereomer Draw a constitutional isomer C 3 C 3 C 2 C 3 C 2 C Draw each structure in a Fischer projection, then decide whether the compound is chiral or achiral. Structure Fischer Chiral or achiral? 22. Draw Fischer projections of the following compounds to help determine their relationship. Are they identical, enantiomers, diastereomers, constitutional isomers, or not related? C 3 C 2 C 3 C 2 C 3 C 3 Page 6

7 23. Identify the relationship between each pair of compounds. Are they identical, constitutional isomers, enantiomers, diastereomers, or not isomers? C 3 C 2 C 3 C 3 C 2 C 3 C 3 C 2 C 2 C 3 C 3 C 3 C 3 C 2 C 3 C 3 C 3 C 3 PTICAL ACTIVITY AND PYSICAL PRPERTIES F STEREISMERS 24. Define the following terms. a. Plane-polarized light b. ptical rotation c. Racemic mixture d. Enantiomeric excess (ee) Page 7

8 25. The product mixture from a chemical reaction is reported as 98 ee. What does this mean? Give the percentages of the components present in the mixture. 26. Would the following pairs of compounds have identical or different physical properties (boiling points, densities, etc.)? int: determine if they re identical, enantiomers, or diastereomers. iefly explain. ief explanation ief explanation Page 8

9 27. Multiple choice. iefly explain each choice. a. Compound A has an optical rotation of 13.2, or [a ]= Compound B should have an optical rotation of (circle one): [a ]= [a ]= [a ]= 0 [a ]= some other number A B b. Compound C has a boiling point of 130 C. Compound D should have a boiling point of (circle one): b.p. = 130 b.p. = 0 C b.p. = some other number C 3 C 3 C C 3 D C 3 c. Compound E has an optical rotation of -8.3, or [a ]= Compound F should have an optical rotation of (circle one): [a ]= -8.3 [a ]= +8.3 [a ]= 0 [a ]= some other number E F d. Compound G has a density of 0.91 g/ml. Compound should have a density of (circle one): d = 0.91 g/ml d = some other number G Page 9