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Stereochemistry Workshop
1. Assign the marked asymmetric centers with R or S designations.
2. Rank each of the following sets of substituents (highest priority substituent = 1; lowest priority substituent = 4). Place the number in the blank below the substituent.
(a)
(b)
3. Determine the relationship between each of the following pairs of structures (enantiomers, diastereomers, constitutional isomers, or identical).
(a)
(b)
(c)
(d)
3. Which of the following structures is different from the other three? Explain.
4. (a) Place asterisks at all of the asymmetric carbon atoms in the molecule shown below (prostacyclin). (b) Based on the number of asymmetric carbons, how many stereoisomers of prostacyclin are possible?
5. Hydrogenation of an alkene will yield an alkane. The alkane formed by hydrogenation of (S)-4-methyl-1-hexene (I) is optically active, while the one formed by hydrogenation of (S)-3-methyl-1-pentene (II) is not. Explain.
I II
6. Draw and label a stereoisomer of this compound that is chiral, and draw two that are achiral.
7. Draw the formula for an unsaturated alkyl chloride (C5H9Cl) that shows:
(a) neither geometric isomerism nor optical activity.
(b) both geometric isomerism and optical activity.
(c) geometric isomerism but not optical activity.
(d) optical activity but not geometric isomerism.
8. How many pairs of enantiomers and/or meso compounds are possible for the following?
a)
b)
9. Draw the enantiomer for each of the following compounds. Draw all diastereomers if they exist.
10. Draw all the possible stereoisomers for 2,3-dibromopentane and identify the relationships between molecules as enantiomers or diastereomers. Label your drawings as A, B, C and D and then discuss their relationships using