CHM 220 Stereochemistry

Transcription

1 CM 220 Stereochemistry Stereocenters 1. ow many stereocenters are there in 2,2,4-tribromo-3-methyl-1-pentanol? (A) 2 (B) 3 (C) 4 (D) 5 2. ow many stereocenters are there in 2,3-dibromo-4-methylpentane? 3. ow many stereocenters are there in cyclohex-3-ene-1,2-diol? 4. ow many stereocenters are present in the following structure? N N N N N 2 5. ow many stereocenters are present in the following structure? N 2 N N Chirality 6. Which of the following molecules are chiral? 1. trans-1-chloro-2-methylcyclopropane 2. cis-1-chloro-2-methylcyclopropane 3. 1-chloro-1-methylcyclopropane 4. cis-1,2-dichlorocyclopropane (C) 1 and 2 (D) 3 and 4

2 7. Which of the following molecules are chiral? 1. 1-chloro-2-methylpropane 2. 2-bromobutane 3. 3-chloropentane 4. 2-chloro-3-methylbutane (C) 1 and 3 (D) 2 and 4 8. Which of the following molecules are achiral? 1. trans-1,2-cyclohexanediol 2. cis-1,2-cyclohexanediol 3. trans-1,4-cyclohexanediol 4. trans-1,3-cyclohexanediol (C) 1 and 2 (D) 3 and 4 9. Which of the following molecules are chiral? 1. 4-chlorocyclopentene 2. 2-chloro-3,4-dimethylpentane 3. trans-2-chlorocyclohexanol 4. cis-3,5-dichlorocyclopentene (C) 1 and 2 (D) 3 and Which of the following molecules are chiral? 1. cis-2-chlorocyclohexanol 2. 2-chloropentane 3. 2-chloro-1-pentene 4. 2-chloropropane 5. 2-chlorobutane 6. cis-3,5-dichlorocyclopentene (A) 1, 2, 5 (B) 2, 4, 6 (C) 1, 2, 4 (D) 4, 5, 6 Stereoisomers 11. What is the maximum number of stereoisomers possible for the following structure? 2 C (A) 2 (B) 4 (C) 8 (D) ow many total stereoisomers are possible for 1,2,3,4-pentanetetraol, and of these, how many are chiral? (A) 8 and 4 (B) 8 and 8 (C) 6 and 4 (D) 4 and 4

3 13. There are X isomers of dimethylcyclopropane of which Y are chiral. Select the right numbers for X and Y. X Y (A) 3 1 (B) 2 2 (C) 2 0 (D) Whcih of the following are stereoisomers? (C) 1 and 4 (D) 2 and Which of the following structures have the meso form? C 3 3 C C 3 3 C C 3 (A) 1 and 2 (B) 3 and 4 (C) 1 and 3 (D) 2 and The following structures are stereoisomers. Which are enantiomers? C 3 C 3 C 3 C 3 C 3 C 3 C 3 C 3 (A) 1 and 2 (B) 3 and 4 (C) 1 and 4 (D) 2 and or the following sets of structures, which pairs are enantiomers? (C) 2 and 3 (D) none 1 2 C 3 3 C 3 3 C 3 C 2 C C 2 C 3 3 C

4 18. What relationship do the following structures have? (C) structural isomers (D) identical 19. What relationship do the following structures have? C 3 C 3 C 3 C 3 (C) structural isomers (D) conformational isomers 20. What relationship do the following structures have? D C 3 D C 3 (C) structural isomers (D) identical 21. What relationship do the following structures have? 3 C C 3 (C) structural isomers (D) identical 22. Which of the following structures are pairs of enantiomers? 3 C C 3 C 2 C 3 C 3 3 C 3 C 2 C C 3 C 2 C 3 C 2 C 3 C 3 (C) 2 and 4 (D) none 23. What is the total number of pairs of enantiomers for the following molecules? C 3 CC 2 C 2 C 3 C 3 C 2 CC 2 C 3 C 2 C 2 C 2 C 2 C 3 C 3 C 2 CC 3 (A) 2 (B) 4 (C) 6 (D) 8

5 24. ow many pairs of diastereomers does 1,2-dimethylcyclopentane have? 25. Which of the following molecules can have diastereomers but not enantiomers? 3 CC CC 2 C 3 2 C CC 2 C 3 3 CC CC 2 C 3 3 C C 3 (A) 1 and 3 (B) 3 and 4 (C) 2 and 5 (D) 4 and Which of the following molecules can have both diastereomers and enantiomers? 3 C C 3 3 CC CC 3 (A) (B) (C) (D) The R/S System 27. What is the R,S configuration for the following structure (remember that this is a isher projection)? C 2 C 2 C 3 C 2 C 3 (A) 3R, 4R (B) 3S, 4S (C) 3R, 4S (D) 3S, 4R 28. What is the R,S configuration for the following structure? C 2 C 2 C 2 2 C (A) 2R, 3R (B) 2R, 3S (C) 2S, 3R (D) 2S, 3S 29. Which of the following structures are designated S? 2 N C 3 3 C 2 C 3 C 3 C C(C 3 ) 3 (A) 1 and 2 (B) 2 and 3 (C) 2 and 4 (D) 1 and 3

6 30. Which of the following structures are designated S? 3 C CC 3 C 2 C 2 2 CC ( 3 C) 3 C 3 C (C) 2 and 3 (D) all C(C 3 ) Which of the following structures have an R configuration? 3 C C 2 1 C 3 C 2 C 2 2 (C) 2 and 4 (D) 3 and 4 C 2 5 C 2 C 2 3 C 3 C 3 C What is the enantiomeric excess for the reaction that gives 66% of the S enantiomer and 33% of the R form? (A) 25% (B) 33% (C) 50% (D) 75% 33. The specific rotation of dextrarotatory tartaric acid is degrees. A mixture of dextrarotatory and levorotatory tartaric acid has a specific rotation of 6.35 degrees. What is the optical purity of the mixture? (A) 25% (B) 33% (C) 50% (D) 75%