Siva_chem341_Chapter 7_Answers

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman8. Give the configurations, respectively, of the following two molecules.A) R and R B) R and S C) S and S D) S and RAns: A9. Which one of the following groups has the highest rank as assigned by the Cahn-Ingold-Prelog system for stereogenic carbons?A) –CH=CH 2 B) –CH 2 OH C) –CH=O D) –CH 2 SHAns: D10. Give the configurations of carbons 1 and 2, respectively, in the structure shown below.A) R and R B) R and S C) S and S D) S and RAns: B11. What is the IUPAC name of the following compound?A) (2S, 3S)-2,3-dibromopentane C) (2R, 3S)-2,3-dibromopentaneB) (2S, 3R)-2,3-dibromopentane D) (2R, 3R)-2,3-dibromopentaneAns: D12. Which of the following statements are true?I. If a molecule has a plane of symmetry it is achiral.II. If a molecule has a center of symmetry it is achiral.III. If a molecule has one stereogenic center it is chiral.A) I and II B) I and III C) II and III D) I, II, and IIIAns: DPage 3Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman23. What is the relationship between the following two compounds?A) identical B) enantiomers C) diastereomers D) constitutional isomersAns: B24. In terms of stereochemistry, the following reaction givesA) a single enantiomer. C) a nonracemic pair of enantiomers.B) a racemic pair of enantiomers. D) two diastereomers.Ans: D25. Which of the following has a meso stereoisomer?I. 2,4-dichloropentaneII. 1,3-dimethylcyclopentaneIII. 2,3-dichloropentaneA) only I B) only II C) I and III D) I and IIAns: DPage 6Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman26. Which of the following amines gives a pair of diastereomeric salts when reacted with(S)-(-)-malic acid?A) only I B) only II C) only III D) I and IIIAns: D27. Which of the following C 6 H 10 cycloalkenes would give a pair of diastereomericepoxides when reacted with peroxyacetic acid, CH 3 CO 3 H?A) 1-methylcyclopentene C) 1,2-dimethylcyclobuteneB) 3-methylcyclopentene D) 3,3-dimethylcyclobuteneAns: B28. The addition of HBr to 1-octene givesA) a racemic mixture of 2-bromooctane.B) a nonracemic mixture of 2-bromooctane.C) 1-bromooctane.D) a racemic mixture of 1,2-dibromooctane.Ans: A29. Compound X, C 6 H 10 , is optically active. Hydrogenation of the compound givesmethylcyclopentane. Which compound below is compound X?A) A B) B C) C D) DAns: CPage 7Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman30. Which of the following is the best method to make a racemic mixture of (+) and (–)–2,3-dibromobutane?A) photochemical bromination of 2-bromobutaneB) addition of HBr to racemic 3-bromo-2-buteneC) addition of Br 2 to cis-2-buteneD) addition of Br 2 to trans-2-buteneAns: C31. Which of the following compounds gives a pair of diastereomers upon epoxidation withperoxyacetic acid, CH 3 CO 3 H?A) A B) B C) C D) DAns: D32. How many stereoisomers are there of D-fructose (including D-fructose), shown below?A) four B) six C) eight D) twelveAns: CPage 8Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman33. Which of the following Fischer projections corresponds to the compound shown below?A) A B) B C) C D) DAns: A34. The four isomeric dimethylcyclopropanes are shown below. Identify two of the isomerswhich are related as diastereomers.A) I and III B) I and IV C) II and III D) III and IVAns: C35. How many stereoisomers are there of 1-isopropyl-4-methylcyclohexane?A) only 1 structure possible - no stereoisomers B) two C) three D) fourAns: B36. Which object below is achiral?A) golf club (wood driver) B) baseball glove C) tennis shoe D) baseball batAns: D37. Which compound below has a meso form?A) 1,2-dichlorobutane C) 2,3-dichlorobutaneB) 1,3-dichlorobutane D) 1,4-dichlorobutaneAns: CPage 9Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman38. Which compound below has no stereoisomers?A) 1,2-dichlorobutane C) 2,3-dichlorobutaneB) 1,3-dichlorobutane D) 1,4-dichlorobutaneAns: D39. Compound X (C 7 H 12 ) is optically active. Hydrogenation of compound X gives twoisomeric 1,2-dimethylcyclopentanes, one is optically active and the other is opticallyinactive. Of the following compounds, which is the only one that fits the data?A) A B) B C) C D) DAns: C40. Which sawhorse drawing below has the identical conformation as the following Fischerprojection?A) A B) B C) C D) DAns: BPage 10Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman44. Which reaction below gives a pair of diastereomers?A) A B) B C) C D) DAns: A45. Which one of the following isomeric dibromobutanes is shown below?A) (2R, 3R)-2,3-dibromobutane C) meso-2,3-dibromobutaneB) (2S, 3S)-2,3-dibromobutane D) (R)-1,2-dibromobutaneAns: CPage 12Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman46. The following isomer of dibromohexane can be synthesized byA) addition of Br 2 to trans-3-hexene. C) addition of HBr to trans-3-hexene.B) addition of Br 2 to cis-3-hexene. D) addition of HBr to cis-3-hexene.Ans: A47. What are the configurations of C(1) and C(2), respectively, for the stereoisomer of 2-methylcyclopentanol shown below?A) (1R, 2R) B) (1R, 2S) C) (1S, 2R) D) (1S, 2S)Ans: B48. Which one of the following is a diastereomer of (2R,3R)-2,3-dibromopentane?A) (2S,3S)-2,3-dibromopentane C) R-1,2-dibromopentaneB) (2S,3R)-2,3-dibromopentane D) (2R,4R)-2,4-dibromopentaneAns: B49. Which of the following is the enantiomer of (2R,3R)-2,3-dibromopentane?A) (2S,3S)-2,3-dibromopentane C) (2R,3S)-2,3-dibromopentaneB) (2S,3R)-2,3-dibromopentane D) (2R,4R)-2,4-dibromopentaneAns: APage 13Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman50. What is the IUPAC name of the following hydrocarbon?A) (R)-4-ethylpentanane C) (S)-2-ethylpentaneB) (S)-3-methylhexane D) (R)-3-methylhexaneAns: B51. What is the total number of stereoisomers (including the one shown) for the followingalcohol?A) zero (none are possible) B) two C) three D) fourAns: B52. Which of the following best describes a racemic mixture?A) A mixture containing equal amounts of two diastereomers.B) A mixture containing a meso stereoisomer.C) A mixture containing unequal amounts of enantiomers.D) A mixture containing equal amounts of enantiomers.Ans: D53. Which one of the isomeric C 4 H 9 Cl molecules is chiral?A) 1-chlorobutane C) 1-chloro-2-methylpropaneB) 2-chlorobutane D) 2-chloro-2-methylpropaneAns: BPage 14Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman54. Which of the following molecules is(are) chiral?A) only I B) I and II C) II and III D) I, II, and IIIAns: A55. How many stereoisomers of 2,3-pentanediol are possible?OHOHA) 2 B) 3 C) 4 D) 6Ans: C56. How many stereoisomers are possible for this structure?OHA) 1 B) 4 C) 8 D) 16Ans: C57. How many stereoisomers of 2,4-pentanediol are possible?HOOHA) 2 B) 3 C) 4 D) 6Ans: CPage 15Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman58. The tartaric acid found in fruits, when isolated, exhibits [α] = +12°. Whichconfiguration is NOT possible for this naturally-occurring material?HOHO 2 COHtartaric acidCO 2 HA) R,R B) R,S C) S,S D) there is no way to tellAns: B59. Which statement would be true of this reaction?CH 3 CH 2 CH 2 CH 3Br 2CH 3 CH 2 CHBrCH 3lightA) The organic product is achiral.B) The product is racemic.C) The product is more of one enantiomer than the other.D) There is no way to guess the stereochemistry.Ans: B60. The most specific description of the relationship between the following two moleculesis:CH 3HCCH 3 CH 2BrandH 3 CHCBrCH 2 CH 3A) identical B) isomers C) enantiomers D) diastereomersAns: A61. What are the R/S assignments in this molecule? (assume the carbons are numbered asshown)OHHO 2 C23OHCO 2 HA) 2S, 3R B) 2S, 3S C) 2R, 3S D) 2R, 3RAns: BPage 16Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman62. What is the most important reason that chiral drugs are typically sold as singleenantiomers?A) one enantiomer is typically a more effective drugB) one enantiomer is typically cheaper to makeC) racemic mixtures have already been patentedD) one enantiomer is typically easier to separateAns: A63. The free-radical bromination of (R)-2-chlorobutane could produce how many monobromo2-chlorobutanes? (count all isomers that could be formed, includingstereoisomers)only (R)HClBr 2light?A) four B) five C) six D) eightAns: C64. (-)-Fenchone can be purchased in 70% optical purity. What ratio of enantiomers ispresent?OA) 70% (-) : 30% (+) C) 55% (-) : 45% (+)B) 85% (-) : 15% (+) D) 60% (-) : 40% (+)Ans: B65. One stereoisomer of the structure below is a poison found in a certain mushroom. Howmany stereoisomers of this structure are possible?HOH 3 CON(CH 3 ) 3A) 4 B) 8 C) 16 D) 32Ans: BPage 17Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 7 Stereochemistry: AnswersProf. Sivaguru Jayaraman66. How many chiral centers are present in histrionicotoxin?A) 2 B) 3 C) 4 D) 5Ans: C67. How many chiral centers are in this molecule?HOmorphineOHOH N CH 3A) 2 B) 4 C) 5 D) 6Ans: CPage 18Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.