6 CHAPTER 1. Which of the following would you expect to have the highest boiling point? A) CH3CH2CH2Br D) CH3CH2CH2F B) CH3CH2CH2I E) CH3CH2CH3 C) CH3CH2CH2Cl Ans: 2. What would be the name of the following?
CH3CH2CHBrCHBrCH(CH3)2
A) 3,4-dibromo-2-methylhexane B) 1,2-dibromo-1-isopropylbutane C) 2,3-dibromohexane Ans: D) E) 3,4-dibromo-5-methylhexane 3,4-dibromo-3-methylhexane
3. What would be the major product of the following reaction?
H3C CH3CH2 H Br
Na+ -CN DMSO
H CN
?
A)
H3C CH3CH2
B)
H3C CH3CH2
H N C
C)
H3C CH3CH2 CN H
D)
H3C CH3CH2
N C H
E)
H3C H CH3CH
Ans: There you are at it again. Good luck.
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4. Which of the following would you expect to react fastest with the nucleophile I- (iodide)? A) CH3CH2CH2Br D) (CH3)2CHCH2Cl B) CH3CH2CH2Cl E) (CH3)3CCH2Br C) (CH3)2CHCH2Br Ans: 5. Predict the major product of the following reaction: Ph H A) Ph H N3 B) Ph N3 C) H N3 Ph D) N3 H E) no reaction occurs Ans: 6. Which of the following would you expect to have the weakest C-X bond? A) CH3Cl B) CH3CH2Br C) CH3F D) CH3CH2I E) (CH3)2CHBr Ans: 7. Which of the following haloalkanes would not undergo the reaction below? R-X + CH3SCH3SR + XA) (CH3)2CHI Ans: B) CH3Cl C) (CH3)3CBr D) CH3CH2Br E) CH3CH2CH2I Ph H I KN3 ?
Hope you can do most of these.
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8. What is the major product of the following reaction: Br A) + PPh3 Br B) C) P D) E) no reaction occurs Ans: 9. Indicate the reagents required to achieve the following transformation: CH3 H Br CH3O H CH3 A)
NaCN
? Br
Ph3P / DMSO
?
CH3 H CN CH3O H CH3
B)
1) NaF 2) KCN
C)
1) NaI 2) NaCN
D)
1) NaOMe 2) HCN / light
E) none of the above Ans:
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10. What reactants are required to achieve the following transformation?
? CN
A) 1. PBr3 2. NaCN B)
C) 1. Br2, h 2. HCN D) 1. SOCl 2 2. KCN E) 1. Br2, h 2. KCN Ans: Could you answer that question if you had to remember the reagents? No list to choose from? 11. To which side (if any) would the following equilibrium lie? CH3CH2S- K+ + A) B) C) D) E) Ans: HOH CH3CH2SH + KOH
to the left to the right equally to the right and left there is no way to tell only SN2, SN1 and E2 reactions are possible
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12. What reactants are required to achieve the following transformation?
OH
?
CN
A) B)
NaCN
1) NaOH 2) KCN
C)
O
1.
Cl
S CH3 , pyridine O
2. KCN D) 1) Br2 / light 2) NaCN none of the above
E) Ans:
That question actually requires knowledge of chapter 8. You know that OH is a poor LG. 13. Several alkyl halides, including iodomethane, are known carcinogens or cancer-suspect materials. To destroy these materials by conversion to non-electrophilic species, you can react them with nucleophiles. Which of the following would be the best for rapidly destroying methyl iodide (iodomethane)? A) CH3OH B) NH3 C) H2O D) NaI E) CH3CO2H Ans: 14. Which of the following is not normally a good leaving group on carbon? A) Br B) OCH3 C) Cl D) OSO2R E) I Ans: 15. Which of the following reagents would best accomplish a typical SN2 reaction? A) CH3OH B) H2O C) HCN D) KCN E) KOtBu Ans:
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16. What would be the organic product of the following reaction? CH3CO2- K+ + H C D A)
O H3C C O D H C CH3
Br CH3
?
+ KBr
B) O H3C C O H3C C) O H3C C O
(racemic)
C
H D
C
H CH3
D
D) all of the above E) none of the above Ans: You probably can figure out the answer, but isn't this a terrible way to draw a structure! I hope you do better on the exam. 17. SN2 substitution at secondary halides and sulfonates is often complicated by competing E2 elimination. Which of the nucleophiles below would you choose to obtain the highest yield in an SN2 reaction with menthyl bromide?
Nu
Br
(SN2)
Nu
A) B) CH3ONa CH3CO2Na C) (CH3)3N D) (CH3)3COK E) C6H5SNa Ans: What you need is a good Nu, which is a poor base.
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18. Arrange the following in order of increasing nucleophilicity.
NH2 NH3
NH4 NH4
NH2 NH4
OH
H 2O OH
OH NH3
H 2O
OH NH2
NH3 H 2O
NH4
NH 3 H2O
H 2O NH2
A) B) C) D) E) Ans:
NH2 NH3
NH4 OH
NH4
H 2O
NH3
OH
NH2
19. The Walden Inversion (inversion of configuration) is associated with which of the following? A) E1 reaction D) SN2 reaction B) free-radical halogenation E) none of the above C) SN1 reaction Ans: 20. Predict the major product of the following reaction: Cl A) Cl P(CH3 )3 B) P(CH3 )3
C) Cl + D) Cl E) Ans: You know about neutral nucleophiles. What type of solvent promotes their SN2 reactions? P(CH3 )3 none of the above HPCH 3
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21. Which of the following can be used to synthesize (R)-2-cyanopentane from (R)-2bromopentane? A) NaBr D) NaCN followed by HI B) NaCN E) this reaction cannot occur C) NaI followed by KCN Ans: You probably need a double inversion (R to S, followed by S to R). 22. What is the correct stereochemistry of the product of the following reaction: Br excess NaCN
Cl A) 3R,4S Ans: B) 2S,3R C) 2R,3S D) 2R,3R E) 3R,4R
23. Which of the following is the best leaving group?
I A) B) Ans: Bet you got that one.
NH 2
C)
HO
D)
F
E)
CH 3O
24. Name the following compound:
Cl
Br
A) B) C) D) E) Ans:
(1S, 2S, 5R)-1-bromo-2-isopropyl-5-chlorocyclohexane (1R, 2R, 5R)-1-bromo-2-isopropyl-5-chlorocyclohexane (1S, 3S, 4R)-1-chloro-3-bromo-4-isopropylcyclohexane (1S, 2S, 4R)-2-bromo-4-chloro-1-isopropylcyclohexane (1R, 2S, 4R)-2-bromo-4-chloro-1-isopropylcyclohexane
Were you tempted to use cis / trans? Not necessary when you assign the absolute configuration. Be sure you understand why
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25. Predict the major product of the following reaction: Cl NaSCH3
A)
SCH3
B)
SCH3
C)
CH3
D)
SCH3
E) no reaction will occur Ans:
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26. If the reaction rate of the following reaction is x, doubling the concentration of KCN would give what rate?
Cl
+ KCN
A) 2x B) x/2 Ans:
C) x2
D) x2/2
E) no change in reaction rate
27. Predict the major product of the following reaction:
CH2 CH3
NaN3
H3 C H I
?
A)
CH2 CH3 H3 C H N3
B)
CH2 CH3 H3 C N3 I
C)
CH2 CH3 N3 H CH3
D)
N3 H CH3 CH2 CH3
E) none of the above Ans: Another Fischer projection. Remember: exchanging two substituents inverts the absolute configuration
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28. Which of the following statements best describes why I is a better nucleophile than F in solution? A) F is a stronger base than I. B) Solvation of F impedes its nucleophilicity compared to I. C) I is a stronger base than F. D) Solvation of I increases its nucleophilicty compared to that of F. E) A and B both offer explanations as to why I is a better nucleophile than F in solution. Ans: 29. For the following reaction what is the most likely product?
Br NaSH acetone
A) B) C) Ans:
SH
SH racemic mixture SH
D) E) no reaction
30. Which of the following statements is true of an SN2 reaction. A) follow a first order rate law B) typically are stereoselective C) the fastest step is the rate-determining step D) the carbocation intermediate adopts a trigonal planar geometry E) all of the above Ans: 31. Which set of reagents will best accomplish the following reaction?
H OH Br H O H
H
A) NaBr, acetone B) H2SO4, H2O C) Br2, hv Ans:
D) E)
NaOEt, DMSO none of the above
Do you remember the intramolecular SN reaction. I showed it to you with an OH ; you make the alkoxide from the alcohol by reacting it with a base. You made it through another set congratulations.
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