29 11 2024 17 13 Chapter 5 practice Department of Chemistry and Earth Sciences Organic Chemistry CHEM 211 fall 2016 Stereochemistry sample problems for practice 1 are isomers which have the same bonding sequence but differ in the orientation of their atoms in space Answer Stereoisomers 2 What term describes the structural relationship between cis 1 2 dimethylcyclopentane and trans 1 3 dimethylcyclopentane A not isomers B constitutional isomers C enantiomers D diastereomers E conformers Answer B 3 What is the structural relationship between the two molecule shown below A constitutional isomers B enantiomers C diastereomers D conformational isomers E not isomers Answer A 5 Which of the following incorrectly describes cis 1 2 dimethylcyclopentane A It is a meso compound B It is achiral C It contains two asymmetric carbons D Its diastereomer is trans 1 2 dimethylcyclopentane E It has an enantiomer Answer E 6 Which of the following terms best describes the pair of compounds shown enantiomers Copyright 2013 Pearson Education Inc 1 about blank 1 9 29 11 2024 17 13 Chapter 5 practice diastereomers or the same compound Answer the same compound 7 Which of the following terms best describes the pair of compounds shown enantiomers diastereomers or the same compound Answer the same compound 8 How many asymmetric carbon atoms are present in the following compound A 0 B 1 C 2 D 3 E 4 Answer B 9 How many asymmetric carbons are present in the compound below Answer none 10 How many asymmetric carbons are present in the compound below Answer 5 11 How many asymmetric carbon atoms are present in the molecule shown Copyright 2013 Pearson Education Inc 2 about blank 2 9 29 11 2024 17 13 Chapter 5 practice A 0 B 1 C 2 D 3 E 4 Answer A 12 How many asymmetric carbon atoms are present in the molecule shown A 0 B 1 C 2 D 3 E 4 Answer C 14 Draw the enantiomer of the molecule shown below Answer 15 Which of the following terms best describes the pair of compounds shown enantiomers diastereomers or the same compound Copyright 2013 Pearson Education Inc 3 about blank 3 9 Answer 29 11 2024 17 13 Chapter 5 practice Answer enantiomers 16 Circle each chiral molecule among those shown below 17 Is the molecule shown below chiral or achiral Answer achiral 18 How many asymmetric carbons are present in the compound below Answer 2 19 Which of the following terms best describes the pair of compounds shown enantiomers diastereomers or the same compound Answer enantiomers Copyright 2013 Pearson Education Inc 4 about blank 4 9 29 11 2024 17 13 Chapter 5 practice 20 Which of the following structures are achiral and meso A 1 2 3 4 B 1 2 C 2 3 D 1 4 Answer D 21 How many asymmetric carbons are present in the compound below Answer 5 22 Label each asymmetric carbon in the molecule below as having the R or configuration S Answer Copyright 2013 Pearson Education Inc 5 about blank 5 9 29 11 2024 17 13 Chapter 5 practice 23 Assign the proper configurational label R or S to each chiral carbon in the molecule below Answer 24 Draw the structure of 1 2 3 stereochemistry properly Answer R S S 1 2 dibromo 3 ethylcyclohexane Take particular care to indicate 25 Captopril is used to treat high blood pressure and congestive heart failure Label the chiral centers as R or S Answer 26 Phantasmidine shown below is found in poisonous frog skin and has analgesic Assign each chiral Copyright 2013 Pearson Education Inc 6 about blank 6 9 29 11 2024 17 13 Chapter 5 practice center as having either R or configuration S Answer 27 Which of the following statements correctly pertains to a pair of enantiomers A They rotate the plane of polarized light by exactly the same amount and in opposite directions B They rotate the plane of polarized light by differing amounts and in opposite directions C They rotate the plane of polarized light by differing amounts and in the same direction D The have different melting points E They have the same melting point but they have different boiling points Answer A S 28 If glyceraldehyde has a specific rotation of 8 7 what is the specific rotation of glyceraldehyde A 0 0 B 8 7 C 8 7 D cannot be determined from the information given Answer C 29 Predict the specific rotation of the compound shown R A It is impossible to predict it must be determined experimentally B Because both asymmetric centers are R the compound is dextrorotatory C Because both asymmetric centers are S the compound is levorotatory D Zero the compound is achiral E Because this compound represents a racemic mixture the compound is dextrorotatory Answer D 30 A newly isolated natural product was shown to be optically active If a solution of 2 0 g in 10 mL of ethanol in a 50 cm tube gives a rotation of 2 57 what is the specific rotation of this natural product Answer 2 57 Copyright 2013 Pearson Education Inc 7 about blank 7 9 29 11 2024 17 13 Chapter 5 practice 31 A mixture of equal amounts of two enantiomers A is called a racemic mixture B is optically inactive C implies that the enantiomers are meso forms D both A and B E none of the above Answer D 32 The specific rotation of pure 2 butanol is 13 5 What of a mixture of the two enantiomeric forms is the form if the specific rotation of this mixture is 7 0 Answer 76 33 Is the molecule shown below chiral or achiral Explain what this means Answer The molecule is chiral because its mirror image is nonsuperimposable 34 Why is the following structure not a meso compound Answer The functional group at the top aldehyde is different from the bottom alcohol and thus there is no internal reflective plane in the molecule 35 Stereoisomers which are not mirror image isomers are Answer diastereomers 36 Which of the following molecules if isolated in its pure form would demonstrate optical activity Copyright 2013 Pearson Education Inc 8 about blank 8 9 29 11 2024 17 13 Chapter 5 practice A both IV and V B both I and III C only II D both III and IV E both I and V Answer A 37 The process by which enantiomers are separated is called Answer resolution Copyright 2013 Pearson Education Inc 9 about blank 9 9