CHE 321 Summer 2010 Exam 2 Form Choose the structure(s) that represent cis-1-sec-butyl-4-methylcyclohexane. I II III

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1 CE 321 Summer 2010 Exam 2 orm 2 Multiple Choice Questions: 60 points 1. Choose the structure(s) that represent cis-1-sec-butyl-4-methylcyclohexane. I II III (A) I only (B) II only (C) I and II only II and III only All of them 2. What is the relationship between the following two structures? (A) Enantiomers (B) Diastereomers (C) Identical Conformers Constitutional isomers 3. Consider the following two reactions. Select the one statement that is true. I + 1 A B II + 2 A B (A) Reaction I proceeds by S N 1 mechanism, while reaction II proceeds by S N 2. (B) Reaction I will proceed faster because substrate 1 is more stable than substrate 2. (C) The major product in reaction I will be B and the major product in reaction II will be A. Reaction II will proceed faster because the carbocation intermediate in reaction II is more stable than the carbocation intermediate in reaction I. Reaction II will proceed faster because substrate 2 is less stable than substrate 1. Page 1 of 7

2 CE 321 Summer 2010 Exam 2 orm 2 4. Select the major product of the following reaction. Na DM No Reaction 5. Select the major product of the following reaction. Na DMS Page 2 of 7

3 CE 321 Summer 2010 Exam 2 orm 2 6. Select the major product of the following reaction. C 3 Na DM C 3 7. Select the major product of the following reaction. C 3 C 3 8. Choose the correct number of possible stereoisomers for 2,5-dichlorohex-3-ene. (A) 2 (B) 3 (C) Page 3 of 7

4 CE 321 Summer 2010 Exam 2 orm 2 9. Select the statement that is not true concerning the following reaction. Nu + Nu (A) If the hydrogen atoms in structure 2 are replaced with methyl groups, then the rate of this reaction would decrease. (B) Increasing the stability of the nucleophile (1) will decrease the rate of the reaction. (C) If chlorine was replaced with fluorine in structure 2, then the energy of the transition state would decrease. The following reaction shows second order kinetics. Using a polar aprotic solvent will help increase the rate of the reaction. 10. Choose the correct IUPAC name for the following compound. I 3 C (A) (2S,4S)-4-bromo-4-iodo-2-methylpentane (B) (2S,4R)-2-bromo-2-iodo-4-methylpentane (C) (S)-2-bromo-2-iodo-4-methylpentane (R)-4-bromo-4-iodo-2-methylpentane (R)-2-bromo-2-iodo-4-methylpentane 11. Choose the order that has the following conformers correctly arranged with respect to increasing stability (A) increasing (B) increasing (C) increasing stability stability stability increasing increasing stability stability Page 4 of 7

5 CE 321 Summer 2010 Exam 2 orm Which of the following compounds are achiral? C C I II III C (A) I only (B) II only (C) I and II only II and III only All of them Short Answer Questions: 40 points 13. or each compound, provide the correct IUPAC name. 10 pts a) b) 5-bromo-2,3-dimethylheptane (S)-pent-4-en-2-ol or (S)-4-penten-2-ol 10 pts All correct 8 pts All correct, except for stereochemistry in (b) 5 pts ne completely correct 2 pts ne minor error in either compound Page 5 of 7

6 CE 321 Summer 2010 Exam 2 orm Draw the most stable conformation of (1S,3S)-1-isopropyl-3-methylcyclohexane. early draw the structure in the chair form, and clearly label all substituents as being axial or equatorial. 10 pts (a) (e) R (a) (e) 10 pts Correct 8 pts Drew a correct structure of the enantiomer. 5 pts Structure correct, but chose least stable conformation R drew a diastereomer. 2 pts ne aspect of structure correct. If no chair form, then no credit. If no axial/equatorial labels where appropriate, then dropped down one level. If labeled as axial, but looks equatorial or vice versa, then dropped down one level. If isopropyl substituent not properly drawn or ambiguous, then dropped down one level. 15. In chapter 6, you learned about 1,2 eliminations. Apply the same principles you learned and, using the curved arrow formalism, draw a mechanism showing all the bond-making and bond-breaking steps of the following reaction. 8 pts + 8 pts All 4 arrows correctly drawn 6 pts 3 arrows correctly drawn 4 pts 2 arrows correctly drawn 2 pts 1 arrow correctly drawn Any additional contradictory arrows drawn resulted in loss of partial credit. Page 6 of 7

7 CE 321 Summer 2010 Exam 2 orm Compounds A through E are five isomeric cyclobutanes with the molecular formula C 5 9. Based on the information given below, determine and clearly draw the structures of A, B, C, D and E, indicating stereochemistry where appropriate, using wedges and dashes. 12 pts a. Treatment of compounds A through D with Na in DM followed second-order kinetics and showed the following relative rates: A > B C D b. Compound E does not undergo S N 2 reaction under the given conditions. c. Compounds A, B, D, and E were found to be achiral. d. Compound C was found to be optically active containing two chirality centers, each having S configuration. e. Compounds B and D are stereoisomers, with compound B being the trans isomer. R A B R R R C R D E 12 pts All correct 9 pts Drew the enantiomer of C, but everything else correct. 6 pts At least two correct assignments (structures must be correct). 3 pts ne correct assignment. (If no wedges and dashes where appropriate, no credit. If more than one compound is drawn in a box, that particular compound letter is considered incorrect.) Page 7 of 7