Exam 0 - PDFs

Chapter 10 Conjugation in Alkadienes and Allylic Systems: Answers Prof. Sivaguru Jayaraman

Page Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

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Chapter 10: Conjugation in Alkadienes and Allylic Systems

1. Identify the allylic halide(s).

A) only II B) I and II C) I and IV D) I, III, and IV Ans: C

2. How many vinylic hydrogens are there in 1-ethylcyclohexene?

A) one B) two C) three D) four Ans: A

3. Which of the following carbocations is the most stable?

A) A B) B C) C D) D Ans: D



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4. What is(are) the expected product(s) of the following reaction?

A) only II B) only III C) I and III D) II and IV Ans: C

5. What is the IUPAC name of the following diene?

A) 3-chloro-2,5-dimethyl-2,6-heptadiene B) 3-chloro-2,5-dimethyl-1,5-heptadiene C) 5-chloro-3,5-dimethyl-1,6-heptadiene D) 5-chloro-3,6-dimethyl-1,5-heptadiene

Ans: D

6. Which of the following are conjugated dienes? I. 1,2-octadiene II. 1,3-octadiene III. 2,5-octadiene IV. 1,7-octadiene

A) only I B) only II C) I and II D) II and III Ans: B

7. Chlorination of 14C-labeled propene (H2

14C=CHCH3) with Cl2 at high temperature would give which of the following chloropropenes?

A) only I B) only II C) I and II D) I and III Ans: C

8. Which compound below has the lowest heat of hydrogenation?

A) 1,5-hexadiene C) 3,4-hexadiene B) (E)-1,4-hexadiene D) (E,E)-2,4-hexadiene

Ans: D



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9. What type or types of stereoisomers are possible for 3,4-heptadiene, shown below? CH3CH2CH=C=CHCH2CH3 A) a pair of enantiomers B) two diastereomers, E and Z C) three diastereomers, (E,E), (E,Z), and (Z,Z) D) no stereoisomers are possible

Ans: A

10. Which of the following compounds most readily undergoes solvolysis with methanol? A) (E)-1-bromo-1-butene C) 3-bromo-1-butene B) 2-bromo-1-butene D) 4-bromo-1-butene

Ans: C

11. What is the product of the reaction sequence shown below?

A) A B) B C) C D) D Ans: B

12. What is the relationship between the s-cis and s-trans forms of 1,3-butadiene?

A) constitutional isomers B) different conformations of the same compound C) diastereomers D) resonance forms

Ans: B



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13. Which compound undergoes 1,4-addition with Br2?

A) A B) B C) C D) D Ans: A

14. Addition of one equivalent of HBr to 1,3-cyclohexadiene gives

A) bromocyclohexane. B) 3-bromocyclohexene. C) 4-bromocyclohexene. D) 3-bromocyclhexene and 4-bromocyclohexene.

Ans: B

15. Which of the following is the 1,4-addition product in the reaction shown below?

A) A B) B C) C D) D Ans: C



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16. What is the kinetically controlled product in the following reaction?


17. Rank the following carbocations in decreasing order of stability.

A) I > II > III B) III > II > I C) II > I > III D) They are of equal stability. Ans: A

18. Give the total number of resonance forms of the carbocation which results from the SN1

ionization of the compound shown below.

A) no resonance forms - a single Lewis structure B) two C) three D) four Ans: C



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19. Which reaction sequence below would work best (and with highest overall yield) in the following conversion?


20. Methanolysis of 4-bromo-2-methyl-2-pentene gives two isomeric substitution products,

one of which is shown. What is the other substitution product?


21. Which one of the following gives only a single allylic bromide on heating with NBS in

carbon tetrachloride?




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22. Which of the following is the product of the intramolecular Diels-Alder reaction shown below?


23. What is the product of the following Diels-Alder reaction?


24. Which one of the following is the s-trans conformation of (E)-2-methyl-2,4-hexadiene?




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25. Identify the weakest carbon-hydrogen bond in the following diene.

A) C-H on C(1) B) C-H on C(2) C) C-H on C(4) D) C-H on C(7) Ans: C

26. Identify the diene and dienophile which would give the following product.




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27. Which dienophile is most reactive with 1,3-butadiene?


28. Which of the following compounds cannot react as a diene in a Diels-Alder reaction?




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29. Identify the diene used in the reaction shown below.




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30. What is the product of the reaction shown below?


31. Which of the following is not true concerning the addition of HCl to 1,3-butadiene?

A) The intermediate is an allylic carbocation. B) A carbocation rearrangement leads to the 1,4-addition product. C) The 1,4-addition product is the thermodynamically controlled product. D) The reaction mechanism has two steps.

Ans: B



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32. Which of the following is the monomer or monomers needed to make the polymer neoprene shown below?




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33. Identify the diene and dienophile needed to make the following Diels-Alder adduct.


34. Allylic bromination of methylenecyclohexane would be expected to give two isomeric

monobromination products. Identify the other isomer.




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35. Which one of the following is not true concerning Diels-Alder reactions? A) The reaction is stereospecific. B) The reaction mechanism has only one step. C) The reaction mechanism involves a resonance stabilized carbocation. D) The diene must be a conjugated diene.

Ans: C

36. Which of the following isomers of C10H12 has the greatest resonance energy (delocalization energy)?


37. Identify the diene needed for the following reaction.

A) 1,3-pentadiene C) 2-methyl-1,3-butadiene B) 1,4-pentadiene D) 1-methyl-1,3-cyclohexadiene

Ans: A

38. Which of the following is the 1,4-addition product of Br2 to 1,3-cyclohexadiene?




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39. The addition of HBr to 1,3-butadiene gives two products. One of the products is shown. Identify the second product.


40. What product do you NOT expect from this reaction?


41. Why is 1,3-cyclopentadiene not sold by ANY chemical suppliers?

A) it cannot be made B) it is too expensive C) it reacts with itself D) it is a gas, and gases are too dangerous to transport

Ans: C



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42. Which would be the most reactive dienophile?


43. Which of the following would react fastest with 1,3-cyclopentadiene?


44. 1,3-cyclopentadiene is known for

A) its unusually high acidity (pKa ~ 16) B) slowly dimerizing at room temperature C) being a good Diels-Alder diene D) all of the above.

Ans: D



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45. What material is cyclopentadiene made from?

A B

C D A) A B) B C) C D) D Ans: B

46. What product will result from this reaction?

O

OCH3+?

CH2

CO2CH3

CH2

CO2CH3

CH2

CO2CH3

CH2

CO2CH3

A B

C D A) A B) B C) C D) D Ans: B

Chapter 11 Arenes and Aromaticity: Answers Prof. Sivaguru Jayaraman


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Chapter 11: Arenes and Aromaticity 1. What is the IUPAC name of the following compound?

A) ortho-ethyliodobenzene C) para-ethyliodobenzene B) para-ethylphenyl iodide D) 1-ethyl-4-iodo-1,3,5-cyclohexatriene

Ans: C

2. How many isomeric dichlorobenzenes are there? A) no isomers - only a single compound B) 2 C) 3 D) 4 Ans: C

3. What is the IUPAC name of the following compound?

A) 4-tert-butyl-3-chlorophenol C) ortho-tert-butylchlorophenol B) 4-tert-butyl-5-chlorophenol D) 2-tert-butyl-meta-chlorophenol

Ans: A


A) 6-phenylheptane C) 2-heptylbenzene B) 2-benzylheptane D) 2-phenylheptane

Ans: D



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5. Which of the following is 2-chloro-4-ethylphenol?


6. What is the correct IUPAC name of the following compound?

A) 1,4-dibromo-3-nitrobenzene C) 2-nitro-1,4-dibromobenzene B) 1,4-dibromo-2-nitrobenzene D) 1-nitro-2,5-dibromobenzene

Ans: B

7. How many isomeric tribromobenzenes are possible? A) one B) two C) three D) four Ans: C

8. Which of the following is not true concerning the structure of benzene?

A) All C-C-C bond angles are exactly 120o. B) The carbon-carbon bonds rapidly alternate between single and double bonds. C) The six hydrogens are equivalent. D) The π bonds are completely conjugated.

Ans: B



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A) 4,6-dichloro-2-benzoic acid C) 3,5-dichlorobenzoic acid B) 2,4-dichlorobenzoic acid D) meta-dichlorobenzoic acid

Ans: C

10. The total number of resonance forms of the cyclopentadienide anion, C5H5¯, is A) two. B) three. C) four. D) five. Ans: D

11. Which of the following ions are aromatic species?

A) I and III B) II and III C) II and IV D) III and IV Ans: B

12. Identify the aromatic compounds.

A) I and II B) III and IV C) I, II, and IV D) all of them Ans: C



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13. How many isomeric bromoanthracenes are there?

A) none, only one structure B) two C) three D) four Ans: C

14. Which of the following reacts at the fastest rate when heated with N-bromosuccinimide

(NBS) and benzoyl peroxide in carbon tetrachloride at 80oC? A) toluene C) isopropylbenzene (cumene) B) ethylbenzene D) tert-butylbenzene

Ans: C

15. The Birch reduction of benzene with sodium in NH3/CH3OH goes by a four-step mechanism. The first step is the A) transfer of a proton from CH3OH to benzene. B) transfer of an electron from Na to benzene. C) transfer of an electron from benzene to NH3. D) transfer of a hydride ion, H¯, from NH3 to benzene.

Ans: B

16. Which species is oxidized in the Birch reduction shown below?

A) benzene B) Na C) CH3OH D) NH3 Ans: B

17. The benzyl carbocation is shown below. Besides the benzylic carbon, identify any other

carbon atoms which carry a partial positive charge based on resonance theory.

A) ortho and para carbon atoms C) meta and para carbon atoms B) meta carbon atoms D) ortho and meta carbon atoms

Ans: A



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18. Side chain oxidations of alkylbenzenes with Na2Cr2O7 and H2SO4/H2O will not work if the alkyl side chain has A) only one carbon. C) benzylic hydrogens. B) four or more carbons. D) no benzylic hydrogens.

Ans: D

19. Which of the following are consistent with the requirements for aromaticity? I. A system with delocalized π electrons in a ring. II. 4n π electrons in the ring. III. All the ring atoms must be carbons. IV. (4n + 2) π electrons in the ring.

A) I and II B) I and IV C) I, II, and III D) I, III, and IV Ans: B

20. Cyclopentadiene is unusually acidic for a hydrocarbon. Why?

A) Cyclopentadiene is aromatic. B) The conjugate base of cyclopentadiene is aromatic. C) Cyclopentadiene is an unstable diradical. D) The conjugate base of cyclopentadiene is an unstable diradical.

Ans: B

21. Which of the following would most readily react with a strong base, such as NaNH2, to form a carbanion?




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22. What is the value of n from Huckel's rule for the following aromatic compound?

A) n = 3 B) n = 4 C) n = 8 D) n = 9 Ans: B

23. The name of the following compound is

A) meta-bromoanisole. C) meta-bromoaniline. B) meta-bromonitrobenzene. D) meta-bromophenol.

Ans: C

24. Which hydrogen atom would be most easily extracted by a bromine atom?

A) 1 B) 2 C) 3 D) 4 Ans: A



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25. What is the product of the reaction shown below?

A) I B) II C) III D) IV Ans: D

26. Propylbenzene is subjected to the sequence of reactions below. What is the final

product?




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27. A compound X, C8H10, is oxidized to benzoic acid with potassium dichromate, K2Cr2O7, in sulfuric acid. What is compound X?

A) para-xylene B) propylbenzene C) styrene D) ethylbenzene Ans: D

28. Acid-catalyzed dehydration of cis-2-phenylcyclopentanol gives

A) 1-phenylcyclopentene. C) 4-phenylcyclopentene. B) phenylcyclopentane. D) 1-phenylcyclopentanol.

Ans: A

29. Predict the major organic product in the following reaction.


30. Which of the following has the fastest rate of SN1 hydrolysis in aqueous acetone?

A) I B) II C) III D) IV Ans: C



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31. Select the best method to convert styrene, C6H5CH=CH2, to 2-phenylethanol with minimal by-product formation. A) H2O, H2SO4 B) (1) BH3-THF (2) H2O2, NaOH C) (1) HBr (2) KOH, H2O D) (1) HBr, peroxides (2) NaOH, H2O

Ans: B

32. Which of the following would be a correct number of π electrons for a planar, monocyclic, completely conjugated polyene to be aromatic?

A) 3 B) 8 C) 18 D) 24 Ans: C

33. Which of the following is an aromatic hydrocarbon?


34. Which of the following has the lowest heat of reaction on catalytic hydrogenation? (4

moles of H2 per mole of hydrocarbon)




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35. In which of the following are carbon-carbon bond lengths arranged in the correct order?


36. Benzene has _______ π molecular orbitals (bonding and antibonding), and the lowest

_________ molecular orbitals are filled with electrons in the ground state. A) three, three B) six, two C) six, three D) twelve, six Ans: C

37. Which of the following ions has a ground state which is predicted to be a diradical by

simple molecular orbital theory?




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38. Identify the site of protonation when one equivalent of HCl is added to the compound below.

A) N-1 B) N-2 C) both N-1 and N-2 (about 50% each) D) neither N-1 or N-2, the compound is not basic

Ans: A

39. What is the hybridization of the nitrogen atom in pyrrole?

A) sp B) sp2 C) sp3 D) 2p Ans: B



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40. Starting with toluene, which sequence of reactions below works best to prepare the following cyclohexadiene compound?


41. Which of the following isomers would you predict has the highest heat of

hydrogenation? A) 1-ethyl-1,4-cyclohexadiene C) 1-ethyl-1,3-cyclohexadiene B) 3-ethyl-1,4-cyclohexadiene D) 5-ethyl-1,3-cyclohexadiene

Ans: B



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42. Which of the following is the product from the reaction sequence shown below?

A) I B) II C) III D) IV Ans: B

43. Which one of following is not a resonance form of the benzyl free radical?




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44. Which one of the following compounds has the fastest SN1 reaction rate with H2O in acetone?

A) I B) II C) III D) IV Ans: A

45. How many π electrons are there in the following polycyclic aromatic hydrocarbon?

A) 6 B) 8 C) 10 D) 14 Ans: C



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46. In the following conformation of styrene, the alignment of the -CH=CH2 group results in

A) maximum conjugation and maximum steric hindrance with the C6H5 group. B) maximum conjugation and minimal steric hindrance with the C6H5 group. C) minimal conjugation and maximum steric hindrance with the C6H5 group. D) minimal conjugation and minimal steric hindrance with the C6H5 group.

Ans: D

47. How many isomeric tetrachlorobenzenes are there? A) two B) three C) four D) five Ans: B

48. 1,3-cyclopentadiene is known for

A) its unusually high acidity (pKa ~ 16) B) slowly dimerizing at room temperature C) being a good Diels-Alder diene D) all of the above.

Ans: D

49. Which of the resonance structures below is most important in explaining why this molecule has a relatively large dipole moment?




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50. Which of these would be most reactive with pure methanol?


51. Considering aromaticity, which of these would be the most acidic?


52. Which statement is true of the hydrogenation of benzene?

A) The ΔHhydrogenation of benzene is greater than three times that of cyclohexene. B) The ΔHhydrogenation of benzene is equal to three times that of cyclohexene. C) The ΔHhydrogenation of benzene is less than three times that of cyclohexene. D) Benzene cannot be hydrogenated under any conditions.

Ans: C

53. From left to right, these two compounds are

A) aromatic and antiaromatic C) antiaromatic and aromatic B) antiaromatic and non-aromatic D) both are antiaromatic

Ans: B

54. When a ______ ______ is on an atom directly attached to a benzene ring, the benzene ring will stabilize it by resonance. A) negative charge C) unpaired electron (a radical) B) positive charge D) all of the above

Ans: D



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55. Where would this reaction occur fastest in this molecule?


56. When treated with acid, pyrrole forms what?


Chapter 12 Reactions of Arenes - Electrophilic Aromatic Substitution: Answers Prof. Sivaguru Jayaraman


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Chapter 12: Reactions of Arenes - Electrophilic Aromatic Substitution

1. What is the product of the following reaction?

A) isobutylbenzene C) sec-butylbenzene B) 2-methyl-1-phenylpropene D) tert-butylbenzene

Ans: D

2. The major product(s) in the nitration of benzoic acid is(are) A) mixture of ortho and para-nitrobenzoic acid. B) nitrobenzene. C) meta-nitrobenzoic acid. D) nitrobenzene and para-nitrobenzoic acid.

Ans: C

3. Which of the following aromatic compounds reacts faster than benzene in electrophilic aromatic bromination?


4. Nitration of benzoic acid has a reaction rate which is __________ than the nitration rate

of benzene and gives primarily the _____________ product(s). A) slower, meta C) faster, ortho,para B) slower, ortho,para D) faster, meta

Ans: A



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5. Which one of the following is the electrophile in the reaction shown below?

A) benzene B) NO3¯ C) NO2

+ D) H2SO4 Ans: C

6. What is the electrophile in the Friedel-Crafts alkylation reaction below?

A) AlCl3 B) Cl¯ C) benzene D) (CH3)3C+ Ans: D

7. Which point on the potential energy diagram corresponds to the species shown to the

right for the electrophilic bromination of benzene with Br2/FeBr3?


8. Which species below best depicts the electrophile in the FeBr3-catalyzed bromination of

benzene?

A) Br2 B) FeBr4- C) D) FeBr3

Ans: C



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9. Which one of the following reactions does not give tert-butylbenzene? A) benzene + (CH3)3CCl/AlCl3 C) benzene + (CH3)3CH/AlCl3 B) benzene + (CH3)2C=CH2/H2SO4 D) benzene + (CH3)3COH/H2SO4

Ans: C

10. Which point on the potential energy diagram corresponds to the species shown to the right for the electrophilic nitration of benzene with HNO3/H2SO4?


11. What is(are) the product(s) of the following reaction?

A) C6H5CH2CH2CH3 B) C6H5CH(CH3)2 C) C6H5CH2CH2CH2C1 D) a mixture of C6H5CH2CH2CH3 and C6H5CH(CH3)2

Ans: D



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12. Which one of the following is not a resonance form of the cyclohexadienyl cation intermediate in the bromination of benzene?


13. How many mononitration products are possible in the nitration of naphthalene, shown

below?

A) only 1 B) 2 C) 3 D) 4 Ans: B

14. Rank the following compounds in order of decreasing reactivity to aromatic

electrophilic bromination. I. benzene II. toluene III. benzoic acid IV. phenol A) IV > II > I > III C) II > I > IV > III B) IV > III > II > I D) II > III > IV > I

Ans: A

15. Which of the following groups are ortho/para directors? I. –NO2 II. –OCH3 III. –CO2CH3 IV. –CH3

A) I and III B) II and III C) II and IV D) III and IV Ans: C



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16. Predict the effect the substituent attached to the benzene ring below would have on electrophilic aromatic substitution reactions?

A) ortho/para director, activator C) meta director, activator B) ortho/para director, deactivator D) meta director, deactivator

Ans: D

17. In the Friedel-Crafts alkylation of benzene, dialkylation is often a significant by-product. In the Friedel-Crafts acylation of benzene, diacylation is not a significant by-product. Which of the following is the primary reason for this difference? A) Alkyl groups activate the ring to further substitution, acyl groups deactivate it. B) Alkyl groups are less sterically hindered than acyl groups. C) Acyl cations are more difficult to make with Lewis acids. D) Unlike acyl cations, carbocations can undergo rearrangements.

Ans: A

18. Which of the following is the best method to make n-butylbenzene?




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19. What is the major product of the following reaction?

A) 4-ethyl-2-nitrophenol C) 1-ethyl-4-nitrobenzene B) 4-ethyl-3-nitrophneol D) 4-nitrophenol

Ans: A

20. Based on resonance theory, what is the approximate charge on the indicated carbon?

A) +1 B) +0.50 C) +0.33 D) +0.20 Ans: C

21. Which isomer of dichlorobenzene gives a single mononitration product?

A) ortho B) meta C) para D) none of them Ans: C

22. Arrange the following compounds in order of increasing reaction rate with

HNO3/H2SO4. I. C6H5CH=O II. C6H5OCH3 III. C6H5Br IV. C6H5CH3 A) I < III < IV < II C) III < I < II < IV B) I < IV < III < II D) III < I < IV < II

Ans: A



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23. Salicylic acid reacts with two equivalents of ICl to give one of the products below. Which one is it? (Hint: Cl is more electronegative than I.)


24. Identify the preferred site(s) of electrophilic attack on the following compound.

A) ortho/para positions on ring 1 C) ortho/para positions on ring 2 B) meta position on ring 1 D) meta position on ring 2

Ans: C

25. Which of the following is the best method to make meta-bromoethylbenzene from benzene?




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26. Which one of the following compounds undergoes electrophilic aromatic sulfonation at the fastest rate?


27. What is the product of the following series of reactions?




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28. Nitration of chlorobenzene has a reaction rate which is __________ than the nitration rate of benzene and gives primarily the _____________ product(s).

A) faster, ortho/para B) faster, meta C) slower, ortho/para D) slower, meta Ans: C

29. What is the major product of the Friedel-Crafts alkylation of benzene with

(CH3)2CHCH2Cl and AlCl3? A) isobutylbenzene C) sec-butylbenzene B) tert-butylbenzene D) butylbenzene

Ans: B

30. Where would the compound shown below undergo bromination with Br2/FeBr3?

A) ortho/para position on ring 1 C) ortho/para position on ring 2 B) meta position on ring 1 D) meta position on ring 2

Ans: A

31. Where would the compound shown below undergo bromination with NBS and benzoyl peroxide?

A) ortho/para position on ring 1 C) C(2) position on ring 2 B) meta position on ring 1 D) methyl group on ring 2

Ans: D



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32. Based on directing effects in electrophilic aromatic substitution reactions, predict the major addition product of the following reaction.


33. Which one of the following substituents is deactivating and ortho-para directing in

electrophilic aromatic substitution reactions? A) –Cl B) –N(CH3)2 C) –CO2H D) –CH=CH2 Ans: A

34. Consider the partial rate factors for electrophilic aromatic substitution at the indicated

position of anisole and nitrobenzene. Which of the following correlates to these partial rate factors?




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35. Starting with toluene, which of the following is the best synthesis of meta-bromobenzoic acid?


36. Predict which position of the naphthalene compound below is the most reactive with

electrophiles in electrophilic aromatic substitution?




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37. Starting with toluene, which of the following is the best method to make the ether shown below? (Assume you can separate ortho and para isomers.)


38. Identify the major product(s) of the reaction sequence shown below.

A) ortho and para-chloroacetophenone C) ortho and para-chlorobenzaldehyde B) meta-chloroacetophenone D) meta-chlorobenzaldehyde

Ans: B



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39. Which of the following is not a valid resonance form of the intermediate species in the reaction shown below?


40. How many mononitration products are possible in the nitration of the compound shown

below?

A) only 1 B) 2 C) 3 D) 4 Ans: B



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A) benzene B) ortho-chloroaniline C) meta-chloroaniline D) aniline Ans: D



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43. Which one of the following has the weakest carbon-chlorine bond?


44. Which compound in each of the following pairs is the most reactive to the conditions

indicated?

A) I and III B) I and IV C) II and III D) II and IV Ans: A

45. Which of the following reacts at the fastest rate with potassium methoxide (KOCH3) in

methanol? A) fluorobenzene C) 2,4-dinitrofluorobenzene B) 4-nitrofluorobenzene D) 2,4,6-trinitrofluorobenzene

Ans: D

46. Which of the following reacts at the fastest rate with potassium methoxide (KOCH3) in methanol? A) fluorobenzene C) p-fluorotoluene B) p-nitrofluorobenzene D) p-bromofluorobenzene

Ans: B



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47. Which of the following is the kinetic rate equation for the addition-elimination mechanism of nucleophilic aromatic substitution? A) rate = k[aryl halide] C) rate = k[aryl halide][nucleophile] B) rate = k[nucleophile] D) rate = k[aryl halide][nucleophile]2

Ans: C

48. Which of the following is not a resonance form of the intermediate in the nucleophilic addition of hydroxide ion to para-fluoronitrobenzene?

A) I B) II C) III D) IV Ans: C

49. Which chlorine is most susceptible to nucleophilic substitution with NaOCH3 in

methanol?

A) #1 C) #1 and #2 are equally susceptible. B) #2 D) No substitution is possible.

Ans: B


A) N,N-dimethylaniline C) phenyllithium (C6H5Li) B) para-chloro-N,N-dimethylaniline D) meta-chloro-N,N-dimethylaniline

Ans: A



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51. Which one of the reagents readily reacts with bromobenzene without heating? A) NaOCH2CH3 B) NaCN/DMSO C) NaNH2/NH3 D) (CH3)2NH Ans: C

52. Which of the following would work best for the synthesis of the ether shown below?




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53. Carbon-14 labelled chlorobenzene is reacted with sodium amide in ammonia as shown below. Which of the following depicts the carbon-14 labeled in the product(s)?




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54. Identify the product(s) of the following reaction.

A) only ortho-methylaniline B) ortho-methylaniline and meta-methyaniline C) meta-methylaniline and para-methyaniline D) ortho-methylaniline and para-methyaniline

Ans: B

55. Which of the following best estimates the percentages of the three isomeric methylanilines from the reaction shown below?




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56. Which of the following is a key intermediate in the reaction shown below?




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57. Identify the diene required for the synthesis shown below.


58. Assume that the following reaction goes by the elimination-addition mechanism for

nucleophilic aromatic substitution. Based on that, how many isomeric naphthylamines are expected in the following reaction?

A) only a single product B) two C) three D) four Ans: C



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59. Which of the following best estimates the percentages of the three isomeric deuterated anilines from the reaction shown below?


60. Which of the following is(are) true concerning the intermediate benzyne?

I. Benzyne is aromatic. II. All the hydrogens of benzyne are equivalent and indistinguishable. III. The benzyne molecule has strain energy.

A) only I B) only III C) I and III D) II and III Ans: C



23

61. Which of the following is(are) true concerning the intermediate in the addition-elimination mechanism of the reaction below?

I. The intermediate is aromatic. II. The intermediate is a resonance stabilized anion. III. Electron withdrawing groups on the benzene ring stabilize the intermediate.

A) only I B) only II C) I and III D) II and III Ans: D

62. Which one of the following has the fastest rate of reaction with sodium ethoxide,

NaOCH2CH3, at 25°C? A) para-fluoronitrobenzene C) para-bromonitrobenzene B) para-chloronitrobenzene D) para-iodonitrobenzene

Ans: A

63. Arrange the following compounds in order of increasing reactivity with sodium methoxide, NaOCH3?

A) I < II < III B) I < III < II C) II < I < III D) III < II < I Ans: B



24

64. Which position on the potential energy diagram corresponds to the species shown for the reaction of para-fluoro (trifluoromethyl) benzene with sodium methoxide?




25

65. Which of the following is the product from the reaction sequence shown below?




26

66. Identify the likely mechanism in the reaction shown below.

A) SN2 C) electrophilic addition-elimination B) SN1 D) nucleophilic addition-elimination

Ans: D

67. Which of the following is NOT a common electrophile in electrophilic aromatic substitution reactions?

A) +SO3H B) +Br C) +CN D) +NO2 Ans: C

68. Ranked in order of decreasing reactivity in electrophilic aromatic substitution reactions,

the order would be (more reactive > less reactive) A) chlorobenzene > toluene > acetophenone B) chlorobenzene > acetophenone > toluene C) toluene > chlorobenzene > acetophenone D) toluene > acetophenone > chlorobenzene

Ans: C

69. Which statement is true in electrophilic aromatic substitution? A) no meta directors have a nitrogen atom directly attached to the ring B) all ortho/para directors make the ring more reactive than benzene C) no meta directors have non-bonding electrons on the atom directly attached to the

ring D) all ortho/para directors have non-bonding electrons on the atom directly attached

to the ring Ans: C



27

70. What would be the most efficient way to make meta-nitrobromobenzene?

A) bromobenzene + HNO3/H2SO4 B) nitrobenzene + Br2/FeBr3 C) either of these approaches would work D) neither of these approaches would work

Ans: B

71. Which one of the common electrophilic aromatic substitution reactions puts an electron donating group on a benzene ring?

A) Br2, FeBr3 B) SO3 + H2SO4 C) RCOCl + AlCl3 D) RCl + AlCl3 Ans: D

72. What major product do you expect?




28

73. How many TOTAL resonance structures can be drawn for this intermediate? (incl. this one)

A) one B) two C) three D) four Ans: D

74. Of the choices given, where would an aromatic substitution occur on this molecule?


75. What major product(s) would you expect from this reaction?




29

76. How would you best accomplish this?

A) 1. SO3, H2SO4, heat; 2. K2Cr2O7, H2SO4 B) 1. K2Cr2O7, H2SO4, heat; 2. SO3, H2SO4 C) either of these would work. D) neither of these would work.

Ans: B

Chapter 3 Conformations of Alkanes and Cycloalkanes: Answers Prof. Sivaguru Jayaraman


1

Chapter 3: Conformations of Alkanes and Cycloalkanes 1. Identify the conformation of butane shown below.

A) anti B) gauche C) skewed D) eclipsed Ans: B

2. What is the IUPAC name of the compound shown in the following Newman projection?

A) 1,1,2,2-tetramethylethane C) 2,2,3,3-tetramethylbutane B) 1,2-dimethylethane D) 2,3-dimethylbutane

Ans: D

3. What is the IUPAC name of the compound shown below?

A) 1,2,3-trimethylbutane C) 2,3,4-trimethylpentane B) 2,3-dimethylpentane D) 2-isopropylbutane

Ans: B



2

4. What is the dihedral (torsion) angle between the two bromine atoms in the following sawhorse drawing?

A) 0o B) 30o C) 60o D) 90o Ans: C

5. At room temperature, the various conformations of butane

A) do not interconvert; only the anti form is present. B) do not interconvert, but all conformations are present. C) interconvert very slowly. D) interconvert very rapidly.

Ans: D

6. Which statement is correct concerning the relative stabilities of the two conformations, A and B, below?

A) A is more stable. B) B is more stable. C) A and B are equal in stabilities. D) A and B are not equal in stability, but the preferred conformation cannot be

determined by inspection. Ans: C



3

7. Identify the spatial relationship of the two chlorine atoms.

A) gauche B) anti C) eclipsed D) twist Ans: B

8. Which statement is correct concerning the relative stabilities of the two conformations,

A and B, below?

A) A is more stable. B) B is more stable. C) A and B are equal in stabilities. D) A and B are not equal in stability, but the preferred conformation cannot be

determined by inspection. Ans: B


A) trans-1,4-dimethylcyclohexane C) trans-1,3-dimethylcyclohexane B) cis-1,4-dimethylcyclohexane D) cis-1,3-dimethylcyclohexane

Ans: A



4

10. What is the dihedral (torsion) angle between the two bromine atoms in the wedge-and-dash drawing below?

A) 60o B) 90o C) 120o D) 180o Ans: D

11. Identify the relationship between the following two structures.

A) constitutional isomers B) stereoisomers C) different conformations of the same compound D) identical

Ans: C

12. Predict which of the following constitutional isomers of C5H10 would have the highest heat of combustion? A) methylcyclobutane C) cis-1,2-dimethylcyclopropane B) cyclopentane D) trans-1,2-dimethylcyclopropane

Ans: C

13. Identify the two atoms anti to the bromine.

A) the equatorial H's on C-2 and C-6 C) C-2 and C-6 B) the axial H's on C-2 and C-6 D) C-3 and C-5

Ans: D



5

14. Cyclohexane adopts the chair conformation rather than a planar structure because I. torsional strain is minimized. II. the C—C—C bond angles are close to 109.5o. III. there are no 1,3-diaxial interactions in a planar structure.

A) only I B) only II C) I and II D) I, II, and III Ans: C


A) constitutional isomers B) stereoisomers C) different conformations of the same compound D) identical

Ans: B

16. The most stable conformation of the compound shown has

A) all methyl groups equatorial. B) equatorial methyl groups at C-1 and C-2, axial at C-4. C) equatorial methyl groups at C-1 and C-4, axial at C-2. D) equatorial methyl groups at C-2 and C-4, axial at C-1.

Ans: D

17. The most stable chair conformation of cis-1-tert-butyl-3-methylcyclohexane has A) both groups equatorial. B) both groups axial. C) the tert-butyl group equatorial and the methyl group axial. D) the tert-butyl group axial and the methyl group equatorial.

Ans: A



6

18. Identify the relationship of the two compounds below.

A) identical B) constitutional isomers C) stereoisomers D) different conformations of the same compound

Ans: C



7

19. Identify the correct stereoisomer and the most stable conformation of the following compound.




8

20. Identify the relationship of the two compounds below.

A) identical B) constitutional isomers C) stereoisomers D) different conformations of the same compound

Ans: A


A) bicyclo[2.2.2]octane C) bicyclo[3.3.3]octane B) bicyclo[2.2.2]hexane D) bicyclo[3.3.3]hexane

Ans: A

22. Which statement below is true concerning the conversion of cis-1,4-dimethylcyclohexane to trans-1,4-dimethylcyclohexane? A) The conversion takes place by chair conformation ring-flipping. B) You cannot do the conversion without breaking covalent bonds. C) The conversion takes place by rotating the C(1)-C(2) bond by 180°. D) The conversion takes place through the skew boat conformations.

Ans: B

23. What is the IUPAC name of the following bicycloalkane?

A) bicyclo[6.3.0]heptane C) bicyclo[4.2.1]hexane B) bicyclo[4.1.0]hexane D) bicyclo[4.1.0]heptane

Ans: D



9


A) identical B) different conformations of the same compound C) stereoisomers D) constitutional isomers

Ans: C



10

25. Which isomer of 1-tert-butyl-3-ethyl-5-methylcyclohexane below is thermodynamically the most stable?


26. What would the C—C—C bond angles be in a planar cyclohexane?

A) 60o B) 90o C) 109.5o D) 120o Ans: D



11

27. Identify the relationship between the following two Newman projections.

A) identical B) stereoisomers C) different conformations of the same compound D) constitutional isomers

Ans: C

28. The IUPAC name of the following compound is

A) cis-1,2-dimethylcyclohexane. C) 1,1-dimethylcyclohexane. B) trans-1,2-dimethylcyclohexane. D) cis-1,3-dimethylcyclohexane.

Ans: A

29. The following structure is

A) cis-1,3-dimethylcyclohexane. C) trans-1,3-dimethylcyclohexane. B) cis-1,4-dimethylcyclohexane. D) trans-1,4-dimethylcyclohexane.

Ans: C



12

30. The sawhorse drawing of butane below is

A) a gauche conformation. B) the anti conformation. C) the least stable eclipsed conformation. D) the most stable eclipsed conformation.

Ans: A

31. The sawhorse drawing of butane below is the

A) least stable staggered conformation. C) least stable eclipsed conformation. B) most stable staggered conformation. D) most stable eclipsed conformation.

Ans: C

32. Which constitutional isomer of dimethylcyclohexane does not exhibit cis-trans isomerism? A) 1,1-dimethylcyclohexane C) 1,3-dimethylcyclohexane B) 1,2-dimethylcyclohexane D) 1,4-dimethylcyclohexane

Ans: A



13

33. What is the estimated dihedral angle between the two methyl groups on the structure shown below?

A) 30o B) 60o C) 90o D) 120o Ans: B

34. Which one of the following is a stereoisomer isomer of trans-1,3-

dimethylcyclopentane? A) 1,1-dimethylcyclopentane C) ethylcyclopentane B) cis-1,2-dimethylcyclopentane D) cis-1,3-dimethylcyclopentane

Ans: D

35. Which of the following best describes the conformation of propane shown below?

A) C(1) - C(2) staggered and C(2) - C(3) staggered B) C(1) - C(2) staggered and C(2) - C(3) eclipsed C) C(1) - C(2) eclipsed and C(2) - C(3) staggered D) C(1) - C(2) eclipsed and C(2) - C(3) eclipsed

Ans: C



14

36. Which one of the following is the butane conformation shown below?

A) gauche B) anti C) skew D) eclipsed Ans: A

37. What is the correct IUPAC name of the following compound?

A) cis-1-ethyl-2-methylcyclohexane C) cis-1-ethyl-6-methylcyclohexane B) trans-1-ethyl-2-methylcyclohexane D) trans-1-ethyl-6-methylcyclohexane

Ans: B

38. Which of the following can have cis-trans stereoisomers? A) 1,1-dimethylcyclobutane C) 1,1,3-trimethylcyclobutane B) 1,3-dimethylcyclobutane D) 1,1,3,3-tetramethylcylclobutane

Ans: B

39. The C—C—C bond angle in cyclopropane is A) 60o. B) 90o. C) 109.5o. D) 120o. Ans: A

40. The most stable conformation of cis-4-methyl-1-tert-butylcyclohexane is a chair

conformation with A) both the -CH3 and -C(CH3)3 equatorial. B) both the -CH3 and -C(CH3)3 axial. C) the -CH3 equatorial and the -C(CH3)3 axial. D) the -CH3 axial and -C(CH3)3 equatorial.

Ans: D



15


A) cis-1,3-dimethylcyclohexane C) cis-1,4-dimethylcyclohexane B) trans-1,3-dimethylcyclohexane D) trans-1,5-dimethylcyclohexane

Ans: B


A) cis-1,2-diethylcyclobutane C) cis-1,3-diethylcyclobutane B) trans-1,2-diethylcyclobutane D) trans-1,3-diethylcyclobutane

Ans: C

43. Which is more stable, cis-1,3-dimethylcyclohexane or trans-1,3-dimethylcyclohexane? A) trans-1,3-dimethylcyclohexane B) cis-1,3-dimethylcyclohexane C) They are equally stable. D) Stabilities of cis, trans stereoisomers cannot be compared.

Ans: B



16

44. What is the relationship between the following two structures?

A) identical B) stereoisomers C) different conformations of the same compound D) constitutional isomers

Ans: D

45. How many alkyl groups would be equatorial in the most stable conformation of the cyclohexane below?

A) one B) two C) three D) four Ans: B

46. Menthol is the most stable isomer of 2-isopropyl-5-methylcyclohexanol. Which

compound is it?




17

47. The planar form of which ring would have bond angles close to the tetrahedral value but is destabilized by eclipsing interactions?

A B C D A) A B) B C) C D) D Ans: C

48. Consider these two molecules; which statement is true?

I II A) I is more stable than II. C) I and II are equally stable. B) II is more stable than I. D) There is no way to predict this.

Ans: B

49. Which of the staggered conformations of 2-methylbutane is most stable?

H

CH3

H

CH3

CH3

H

H

CH3

H

CH3

H

H3C

H

H3C

H

CH3

CH3

H

H

CH3

H

CH3

CH3

H

A B C D A) A B) B C) C D) D Ans: A

50. What would be the least stable isomer of 1,2,3,4,5,6-hexamethylcyclohexane?

A B C D A) A B) B C) C D) D Ans: A



18

51. What is the most specific name for the conformation shown?

CH3

H H

CH3H

H

A) anti B) staggered C) gauche D) eclipsed Ans: C

52. β-D-Glucose is the six-carbon sugar with all non-hydrogen groups equatorial. Which

structure is it?

O

OH

OH

HO

HO

CH2OH

O

OH

OH

HO

HO

CH2OH

O

OH

OH

HO

HO

CH2OH

O

OH

OH

HO

HO

CH2OH

A B C D A) A B) B C) C D) D Ans: B

Chapter 4 Alcohols and Alkyl Halides: Answers Prof. Sivaguru Jayaraman


1

Chapter 4: Alcohols and Alkyl Halides 1. What is the IUPAC name of the compound below?

A) 5,5-dimethyl-2-hexanol C) 5,5-dimethyl-2-pentanol B) 2,2-dimethyl-5-hexanol D) 2,2-dimethyl-5-pentanol

Ans: A

2. What is the IUPAC name of the compound below?

A) 3-isobutyl-2-hexanol C) 2-methyl-5-propyl-6-heptanol B) 2-methyl-5-(1-hydroxyethyl)octane D) 6-methyl-3-propyl-2-heptanol

Ans: D

3. What is the IUPAC name of the compound below?

A) 8-chloro-4-isopropyl-4,7-dimethylnonane B) 2-chloro-6-isopropyl-3,6-dimethylnonane C) 2-chloro-3,6,7-trimethyl-6-propyloctane D) 6-sec-butyl-2-chloro-3,6-dimethyloctane

Ans: B

4. Rank the following three compounds in order of increasing boiling point. I. CH3CH2CH3 II. CH3CH2OH III. CH3OCH3

A) I < II < III B) I < III < II C) II < III < I D) II < I < III Ans: B



2


A) cis-3-methylcyclohexanol C) cis-5-methylcyclohexanol B) trans-3-methylcyclohexanol D) trans-5-methylcyclohexanol

Ans: B

6. Which of the following is isobutyl alcohol? A) CH3CH2CH2CH2OH C) (CH3)2CHCH2OH B) CH3CH2CH(OH)CH3 D) (CH3)3COH

Ans: C

7. Identify the tertiary alcohol(s).

A) only I B) only II C) only III D) both I and III Ans: C

8. Identify the tertiary halide(s).

A) I and II B) II and III C) III and IV D) only IV Ans: C

9. What is the hybridization of the oxygen atom in alcohols?

A) sp B) sp2 C) sp3 Ans: C



3

10. What is the nucleophile in the following substitution reaction?


11. The C—O—H bond angle in alcohols is closest to

A) 90o. B) 109.5o. C) 120o. D) 180o. Ans: B

12. Rank the following alcohols in order of increasing reaction rate with HBr.

A) II < III < I B) III < II < I C) I < III < II D) I < II < III Ans: C

13. Chlorination of pentane gives a mixture of isomers having the molecular formula

C5H11Cl. The percentage of 1-chloropentane is 22%. Assuming the secondary hydrogens in pentane are equally reactive to monochlorination, what is the percentage of 3-chloropentane in the mixture?

A) 48% B) 26% C) 22% D) 14% Ans: B

14. Which one of the following gives a single monochlorination product?

A) 2,2-dimethylpropane C) 2,3-dimethylbutane B) 2,2-dimethylbutane D) 2-methylpropane

Ans: A

15. Which of the following hydrocarbons has the slowest reaction rate with Br2 and light? A) CH4 B) CH3CH2CH3 C) CH3CH2CH2CH3 D) (CH3)3CH Ans: A



4

16. Which method or methods would work to quantitatively prepare a sodium ethoxide solution? I. CH3CH2OH + NaOH II. CH3CH2OH + NaH III. CH3CH2OH + Na

A) I and II B) I and III C) II and III D) I, II, and III Ans: C

17. What are the products of the following reaction?

A) 1-bromobutane and water C) butane and HOBr B) 1-bromobutane and hydrogen D) CH3CH2CH2CH2OBr + hydrogen

Ans: A

18. Which of the following is not a good method to make bromocyclopentane? A) cyclopentanol plus HBr C) cyclopentanol plus PBr3 B) cyclopentanol plus NaBr D) cyclopentane plus Br2 with light

Ans: B

19. Which of the following is most reactive with HBr? A) CH3OH B) CH3CH2OH C) (CH3)2CHOH D) (CH3)3COH Ans: D

20. Arrange the following alcohols in order of their decreasing reactivity with HBr (most

reactive first).

A) I > II > III B) I > III > II C) III > I > II D) II > III > I Ans: B



5

21. Arrange the following carbocations in order of their decreasing stabilities (most stable first).

A) I > II > III B) III > II > I C) I > III > II D) II > III > I Ans: C

22. How many monochlorination products do you expect in the following reaction?

A) two B) three C) four D) five Ans: C

23. Which of the following is the most stable radical?




6

24. Which of the following are the chain propagating steps in the free radical chlorination of methane?

A) I and III B) II and VI C) III and IV D) III and V Ans: D


BrCH2CH2CH2CH2OH + SOCl2 → A) ClCH2CH2CH2CH2OH C) BrCH2CH2CH2CH2Cl B) BrCH2CH2CH2CH2SH D) ClCH2CH2CH2CH2SOCl

Ans: C

26. Calculate ΔH° of reaction for the free radical bromination of cyclopentane to give bromocyclopentane.

A) –121 kJ/mol B) –63 kJ/mol C) +121 kJ/mol D) +63 kJ/mol Ans: B

27. Which constitutional isomer of C6H14 gives only two monochlorination products?

A) 2-methylpentane C) 2,2-dimethylbutane B) 3-methylpentane D) 2,3-dimethylbutane

Ans: D



7

28. Consider the following reaction (X = Cl or Br).

Which statement(s) is(are) correct? I. Statistically the 1-halopropane should be the major isomer. II. The 2-halopropane to 1-halopropane ratio is largest when X=Br. III. The 2-halopropane to 1-halopropane ratio is the largest when X=Cl.

A) only II B) only III C) I and II D) I and III Ans: C

29. The central carbon of the tert-butyl carbocation, (CH3)3C+, is

A) sp2 hybridized with a +1 formal charge. B) sp2 hybridized with a 0 formal charge. C) sp3 hybridized with a +1 formal charge. D) sp3 hybridized with a 0 formal charge.

Ans: A

30. What are the C—C—C bond angles in the tert-butyl carbocation, (CH3)3C+? A) 60o B) 90o C) 109.5o D) 120o Ans: D

31. Studies indicate that the methyl radical is trigonal planar. Based on this, which of the

following best describes the methyl radical? A) The carbon is sp2 hybridized and the unpaired electron occupies an sp2 orbital. B) The carbon is sp2 hybridized and the unpaired electron occupies a 2p orbital. C) The carbon is sp3 hybridized and the unpaired electron occupies an sp3 orbital. D) The carbon is sp3 hybridized and the unpaired electron occupies a 2p orbital.

Ans: B



8

32. Dibromination of isopropylcyclopentane gives a product which can be isolated in good yields. Which of the following would you predict to be this product?


33. Which of the following is the key intermediate in the chlorination reaction below?




9

34. The structure below is a generalized abbreviation for which class of compounds?

A) ketones B) aldehydes C) carboxylic acids D) esters Ans: B

35. Identify the functional group in the boxed area.

A) ester B) ketone C) carboxylic acid D) ether Ans: A


A) 3-methyl-2-butanol C) 2-methyl-2-butanol B) 3-methyl-3-butanol D) 2,2-dimethyl-1-butanol

Ans: C



10

37. What is the name of the following compound?

A) cis-3-methylcyclohexanol C) cis-2-methylcyclopentanol B) trans-3-methylcyclohexanol D) trans-3-methylcyclopentanol

Ans: B

38. Which of the following mechanistically depicts the protonation of tert-butyl alcohol by hydrogen bromide?


39. How many C3H6Cl2 constitutional isomers do you expect in the dichlorination of

propane? A) two B) three C) four D) five Ans: C



11

40. What is the IUPAC name of the following alcohol?

A) trans-4-methylcyclohexanol C) trans-3-methylcyclohexanol B) cis-4-methylcyclohexanol D) cis-3-methylcyclohexanol

Ans: A

41. Upon free-radical chlorination, the alkane shown would yield

C C C

C

C

A) a single monochloride C) three isomeric monochlorides B) two isomeric dichlorides D) four isomeric monochlorides

Ans: D

42. What is the major product in the mono-chlorination of pentane?

C C C C C C C C C C C C C C C

Cl Cl Cl

A B C

D. none of these is formed.




12

43. If the compound below containing three types of alcohols were exposed to ONLY 1 equivalent of HCl, what major product would you expect?

OH

OHHOCH2

1 HCl?

OH

OHClCH2

Cl

OHHOCH2

OH

ClHOCH2

A B C

D: there is no way to know. A) A B) B C) C D) D Ans: B

44. Which of these five-carbon alcohols would you expect to be most water soluble?

OHOH OH

OH

A B C D A) A B) B C) C D) D Ans: B

45. The reaction shown below is what type?

Cl• + CH4 HCl + H3C•

A) addition B) termination C) propagation D) initiation Ans: C

46. Which halogen forms the weakest bond to carbon?

A) F B) Cl C) Br D) I Ans: A



13

47. If you wanted to get the best yield of compound B from compound A, you would:

X

compound Bcompound A

?

A) use chlorine + light rather than bromine + light B) use bromine + light rather than chlorine + light C) neither would give >50% yield D) either would give >50% yield

Ans: A

48. Where would this reaction occur fastest in this molecule?

Br2

light?

AB

CD


Chapter 5 Structure and Preparation of Alkenes - Elimination Reactions: Answers Prof. Sivaguru Jayaraman


1

Chapter 5: Structure and Preparation of Alkenes – Elimination Reactions

1. Carbon-carbon double bonds do not freely rotate like carbon-carbon single bonds. Why? A) The double bond is much stronger and thus more difficult to rotate. B) Overlap of the two 2p orbitals of the π bond would be lost. C) The shorter bond length of the double bond makes it more difficult for the

attached groups to pass each other. D) Overlap of the sp2 orbitals of the carbon-carbon σ bond would be lost.

Ans: B


A) 2,5-dimethyl-1-hexene C) 2,5-dimethyl-2-hexene B) 1,4-dimethyl-1-hexene D) 2,5-dimethyl-5-hexene

Ans: A


A) 2-methyl-3-propyl-2-pentene C) 4-ethyl-5-methyl-4-hexene B) 3-ethyl-2-methyl-2-hexene D) 4-methyl-3-propyl-3-pentene

Ans: B


A) 3-ethyl-8-methyl-3-nonene C) 1,1-diethyl-6-methyl-3-heptene B) 7-ethyl-2-methyl-6-nonene D) 3-ethyl-7-isopropyl-3-octene

Ans: A

5. How many isomeric alkenes of formula C4H8, including stereoisomers, are possible? A) two B) three C) four D) five Ans: C



2

6. How many isomeric alkenes of formula C5H10, including stereoisomers, are possible? A) three B) four C) five D) six Ans: D


A) 3-bromo-2-methylcyclohexene C) 6-bromo-1-methylcyclohexene B) 1-bromo-2-methyl-2-cyclohexene D) 2-bromo-1-methylcyclohexene

Ans: C


A) 3-ethyl-propyl-1-heptene C) 4,6-diethyl-1-octene B) ethyl-3-vinyloctane D) 3,5-diethyl-1-octene

Ans: D

9. Which of the following alkenes exhibit E-Z isomerism?

CH3CH2CH CHCH2CH3

(CH3)2C CHCH3

CH3CH2CH CHBr

H2C CHCH2CH(CH3)2

I.

II.

III.

IV. A) I and II B) I and III C) II and IV D) I, II, and III Ans: B

10. Which of the following alkenes exhibit E-Z isomerism?

I. 1-chloropropene II. 2-chloropropene III. 3-chloropropene A) only I B) I and II C) II and III D) I and III Ans: A



3


A) (E)-3-bromo-1-fluoro-2-methylpropene B) (Z)-3-bromo-1-fluoro-2-methylpropene C) (E)-1-bromo-3-fluoro-2-methylpropene D) (Z)-1-bromo-3-fluoro-2-methylpropene

Ans: A

12. Which of the following C6H12 isomers has the highest heat of combustion? A) 1-hexene B) trans-3-hexene C) cis-3-hexene D) 2-methyl-2-pentene Ans: A

13. Identify the major organic product expected from the acid-catalyzed dehydration of 2-

methyl-2-pentanol. A) 2-methyl-1-pentene C) 3-methyl-1-pentene B) 2-methyl-2-pentene D) cis-3-methyl-2-pentene

Ans: B

14. Which alcohol below would undergo acid-catalyzed dehydration most readily?


15. What is the slow, rate-determining step, in the acid-catalyzed dehydration of 2-methyl-

2-propanol?

A) Protonation of the alcohol to form an oxonium ion. B) Loss of water from the oxonium ion to form a carbocation. C) Loss of a β-hydrogen from the carbocation to form an alkene. D) The simultaneous loss of a β-hydrogen and water from the oxonium ion.

Ans: B



4

16. Which of the following carbocations is(are) likely to undergo a rearrangement?

A) only I B) I and III C) II and III D) I, II, and III Ans: D

17. Predict the major product of the following reaction.


18. Which of the following expressions is the experimentally observed rate law for an E2

reaction of an alkyl halide? A) rate = k[RX] B) rate = k[RX][base] C) rate = k[RX]2 D) rate = k[base] Ans: B

19. Which of the following most readily undergoes an E2 reaction with sodium ethoxide

(NaOCH2CH3)? A) (CH3)3CF B) (CH3)3CCl C) (CH3)3CBr D) (CH3)3CI Ans: D



5

20. How many isomeric alkenes are possible, including stereoisomers, in the following reaction?

A) two B) three C) four D) five Ans: B

21. In the dehydrohalogenation of 2-bromobutane, which conformation below leads directly

to the formation of cis-2-butene?

A) only I B) only II C) only III D) I and II Ans: A

22. Which of the following cannot undergo an E2 reaction?

A) only I B) only II C) only III D) I and III Ans: A

23. Which of the following would you predict to be the best method for doing the following

conversion with the highest yield?

A) H2SO4, heat B) NaOCH2CH3 C) H3PO4 D) (1) PBr3 (2) KOC(CH3)3 Ans: D



6

24. When a strong base is used in the elimination reaction of an alkyl halide the mechanism, in general, is A) E1. B) E2. C) E1 for tertiary halides, E2 for primary and secondary halides. D) E2 for tertiary halides, E1 for primary and secondary halides.

Ans: B

25. Which of the following sets of conditions most favors the E1 mechanism? A) when the alkyl halide is tertiary and the base is a weak base B) when the alkyl halide is tertiary and the base is a strong base C) when the alkyl halide is primary or secondary and the base is a weak base D) when the alkyl halide is primary or secondary and the base is a strong base

Ans: A

26. Which of the following would have the fastest rate of reaction to form 4-tert-butylcyclohexene?




7

27. What is the first step in the mechanism of the dehydration reaction of a tertiary alcohol with sulfuric acid to form an alkene? A) the loss of OH– to form a carbocation B) the protonation of the hydroxyl group C) the loss of the proton from the hydroxyl group to give an alkoxide ion D) the removal of a β-hydrogen from the alcohol

Ans: B

28. Which of the following does not give 1,2-dimethylcyclohexene as one of the acid-catalyzed dehydration products?


29. Including E-Z isomers, how many E2 products are possible in the following reaction?

A) one B) two C) three D) four Ans: C

30. Which of the following compounds gives a single E2 product on reaction with sodium

ethoxide, NaOCH2CH3?

A) I and II B) I and III C) II and III D) I, II, and III Ans: B



8

31. Which of the following will give 2-methyl-1-butene as the only alkene product on treatment with KOC(CH3)3 in dimethyl sulfoxide? A) 2-bromo-3-methylbutane C) 2-bromo-2-methylbutane B) 1-bromo-3-methylbutane D) 1-bromo-2-methylbutane

Ans: D

32. If the following E2 reaction proceeds through an anti-periplanar transition state, what product or products are expected?

CH3

Cl

KOC(CH3)3

(CH3)3COH

A) only 1-methylcyclohexene B) only 3-methylcyclohexene C) only 4-methylcyclohexene D) equal amounts of 1-methylcyclohexene and 3-methylcyclohexene

Ans: B

33. Which of the following stereoisomers gives the exclusive E2 product shown?




9

34. Zaitsev's rule can be used to predict the major product for which of the following reactions? A) 2-methylpentane + Br2(with light) B) 2-bromo-2-methylpentane + NaOCH2CH3 (in ethanol) C) 2-methyl-2-pentanol + PBr3 D) 2-methyl-2-pentanol + HCl

Ans: B

35. The acid-catalyzed dehydration of the alcohol shown below gives a major product which results from a carbocation rearrangement. Identify this major product.


36. Consider the following reaction.

R = –CH3 or –C(CH3)3 Which statement(s) below is(are) correct? I. X is the major product based on Zaitsev's rule. II. The X:Y ratio is greater when R = –CH3 than when R = –C(CH3)3. III. The X:Y ratio is greater when R = –C(CH3)3 than when R = –CH3.

A) I and II B) I and III C) only II D) only III Ans: A

37. How many different E2 products are expected in the reaction of 3-bromo-1,1-

dimethylcyclohexane with NaOCH2CH3? A) only 1 B) 2 C) 3 D) 4 Ans: B



10

38. Which one of the following compounds cannot undergo an E2 reaction? A) 1-bromo-2,2-dimethylbutane C) 1-bromo-3,3-dimethylbutane B) 1-bromo-2,3-dimethylbutane D) 2-bromo-2,3-dimethylbutane

Ans: A

39. What is the major product of the reaction sequence shown below?

A) 2-methyl-1-butene C) 3-methyl-1-butene B) 2-methyl-2-butene D) 2-methylbutane

Ans: B

40. Which of the following compounds gives 4,4-dimethylcyclohexene as the exclusive E2 product?

A) A B) B C) C D) both A and B Ans: A

41. How many stereoisomers are possible for the following diene?

CH3CH=CHCH2CH2CH=CHCH2CH2CH3

A) only 1 B) two C) three D) four Ans: D



11

42. Based on Zaitsev's rule, which of the following is the major product of the reaction below?


43. Which of the alkenes below has the Z-configuration?

H3CCH3

Cl

OCH3

HOCH3

CH3

CH3

H3CCH3

N

CH2CH3

H3CCH3

H3CO

OCH3

H3C CH3

A) B)

C) D)




12

44. Which alkene of formula C5H10 gives off the least heat (per mol) when burned?

A) B)

C) D)


45. When a C=C is present in a molecule, what is the minimum number of atoms that must

lie in a single plane? A) 2 B) 4 C) 6 D) 8 Ans: C

46. If you wanted to make compound III, starting with compound I or II, what would you

do?

OH

Br

I

II

III

?

?

A) React I with H2SO4. B) React II with NaOEt. C) Either of the reactions in A or B above would work. D) Neither of the reactions in A or B above would work.

Ans: B



13

47. Which compound would react slowest with KOtBu?

Br Br

Br Br

D D

D D

A B

C D A) A B) B C) C D) D Ans: A

48. Which reagent accomplishes the following?

OH

?

Cl

A) HCl B) Cl2, light C) SOCl2 D) NaCl Ans: C

49. What would be the proper name of the molecule below?

A) (E)-2-ethyl-2-butene C) (E)-3-methyl-2-pentene B) (Z)-3-methyl-3-pentene D) (Z)-2-isohexene

Ans: C

Chapter 6: Reactions of Alkenes ‐ Addition Reactions: Answers Prof. Sivaguru Jayaraman


1

Chapter 6: Reactions of Alkenes - Addition Reactions 1. Which one of the following is not a metal catalyst for the hydrogenation of an alkene?

A) Pd B) Pt C) Na D) Ni Ans: C

2. What is(are) the product(s) in the Pd-catalyzed hydrogenation of 1,2-

dimethylcyclopentene? A) trans-1,2-dimethylcyclopentane B) cis-1,2-dimethylcyclopentane C) a mixture of trans and cis-1,2-dimethylcyclopentane D) 1,1-dimethylcyclopentane

Ans: B

3. Which of the following alkenes is expected to have the highest heat of hydrogenation? A) 1-pentene B) trans-2-pentene C) cis-2-pentene D) 2-methyl-2-butene Ans: A

4. Which alkene below is thermodynamically the most stable?

A) 1-hexene B) trans-3-hexene C) cis-3-hexene D) 2-methyl-2-pentene Ans: D

5. The stereochemical pathway for the hydrogenation of an alkene with a metal catalyst,

such as platinum, occurs via A) syn addition. C) Markovnikov addition. B) anti addition. D) anti-Markovnikov addition.

Ans: A

6. The product(s) in the following reaction is(are)

A) only trans-1-4-dimethylcyclohexane. B) only cis-1-4-dimethylcyclohexane. C) both trans and cis-1-4-dimethylcyclohexane. D) methylcyclohexane.

Ans: C



2





3

8. What is the intermediate in the following reaction?


9. Which of the following is not a possible reaction of a carbocation?

A) addition of a nucleophile B) rearrangement to a more stable carbocation C) addition of a proton to form an alkane D) loss of a β-hydrogen to form an alkene

Ans: C

10. Addition of HCl to 3-methyl-1-pentene gives two products. One of these is 2-chloro-3-methylpentane. What is the other product? A) 1-chloro-3-methylpentane C) 3-chloro-2-methylpentane B) 3-chloro-3-methylpentane D) 2-chloro-2-methylpentane

Ans: B

11. Predict which of the following alkenes reacts the fastest with HCl. A) CH3CH2CH2CH2CH=CH2 C) trans-CH3CH2CH=CHCH2CH3 B) cis-CH3CH2CH=CHCH2CH3 D) (CH3)2C=CHCH2CH3

Ans: D



4

12. Which species below is the intermediate in the free radical addition of HBr to 1-butene?


13. Which reagent(s) below would work best in converting 2-methyl-2-hexene to 2-methyl-

3-hexanol? A) (1) H2SO4 (2) H2O B) 50% H2SO4/H2O C) (1) BH3/THF (2) H2O2, NaOH D) Br2/H2O

Ans: C



5



15. What is(are) the product(s) of the following hydroboration-oxidation reaction?

A) 1-methylcyclobutanol C) cis-2-methylcyclobutanol B) trans-2-methylcyclobutanol D) equal amounts of 2 and 3

Ans: B

16. The hydroboration-oxidation reaction can be characterized as the ___________________ to an alkene. A) anti-Markovnikov syn addition of water B) anti-Markovnikov anti addition of water C) Markovnikov syn addition of water D) Markovnikov anti addition of water

Ans: A



6


A) 1,2-dibromo-2-methylhexane C) 2,3-dibromo-2-methylhexane B) 2,2-dibromo-2-methylhexane D) 2,4-dibromo-2-methylhexane

Ans: C

18. Which of the following alkenes gives 1-bromo-2-methyl-2-pentanol upon reaction with Br2/H2O?


19. Rank the following in order of decreasing reactivity with bromine, Br2.

A) I > II > III B) II > III > I C) III > I > II D) III > II > I Ans: A

20. Which of the following is least likely to react with an alkene?




7

21. Which of the following series of reactions would convert cyclohexanol to 1,2-epoxycyclohexane?


22. Which species below acts as the nucleophile in the acid-catalyzed addition of water to

an alkene? A) H3O+ B) the carbocation C) OH- D) H2O Ans: D



8

23. Addition of hypobromous acid, HOBr, to 1-methylcyclohexene gives:


24. A compound, C15H24, is reacted with excess hydrogen using a metal catalyst. One

equivalent of the compound consumed three equivalents of hydrogen. How many rings did the original compound have?

A) 1 only B) 2 only C) 3 only D) none Ans: A

25. A compound, C20H30, can be hydrogenated with platinum metal and hydrogen to give a

compound C20H38. How many double bonds (DB) and rings (R) does the original compound have? (The original compound has no triple bonds.)

A) 4 DB, 2 R B) 4 DB, 1 R C) 3 DB, 3 R D) 2 DB, 4 R Ans: A

26. Determine the SODAR (sum of double bonds and rings) for a compound with the

formula of C6H9BrO. A) one B) two C) three D) four Ans: B



9

27. The reaction of 1-butene with bromine, Br2, in aqueous solution gives primarily 1-bromo-2-butanol. Identify the nucleophilic species in the reaction.

A) Br2 B) C) H2O D) HOBr

Ans: C

28. A compound is treated with ozone followed by zinc in water to give the following three products. Which structure below best fits the data?


29. Which of the following gives acetone, (CH3)2C=O, as one of the products of its

ozonolysis?




10

30. Which of the following species is the intermediate in the bromination of propene?


31. A compound, C7H13Cl, is reacted with sodium ethoxide and gives a single elimination

product, C7H12. Treatment with ozone followed by zinc and water gives the compound below. Identify the original compound.

A) 2-chloro-1,1-dimethylcyclopentane C) 4-chloro-1,2-dimethylcyclopentane B) 1-chloro-1,2-dimethylcyclopentane D) 2-chloro-1,3-dimethylcyclopentane

Ans: D



11

32. Which of the following correctly depicts the mechanistic first step in the addition of HBr to 2-methylpropene?


33. The rearrangement which occurs in the following reaction can be described as a

A) hydride shift from C-2 to C-1. C) proton shift from C-2 to C-1. B) hydride shift from C-3 to C-2. D) methyl group shift from C-3 to C-2.

Ans: B



12

34. Which structure corresponds to the trimer of (CH3)2C=CH2 formed under conditions of cationic polymerization?


35. Which of the following does not give 1-bromo-1-methylcyclopentane as the major

product?




13

36. Which point on the potential energy diagram corresponds to the species below for the reaction of 2-methylpropene with hydrogen chloride?


37. Identify the nucleophile in the following electrophilic addition reaction.




14

38. Which of the following is the rate-determining step in the acid-catalyzed addition of water to 2-methylpropene?


39. Which reaction sequence below would work best in converting 3-pentanol into 2,3-

dibromopentane?




15

40. Which reaction proceeds by anti addition?


41. Which point on the potential energy diagram corresponds to the carbocation

intermediate, (CH3)3C+, for the reaction shown below?




16

42. Which of the following reactions occurs by a one-step mechanism as opposed to a two-step mechanism?


43. What is the product in the following reaction?

A) (CH3CH2CH2)3B B) [(CH3)2CH]3B C) CH3CH2CH3 D) polypropylene Ans: A

44. Identify the following polymer.

A) polyethylene B) polypropylene C) polyisobutylene D) polybutylene Ans: B



17

45. Which of the following is the product of the reaction shown below?


46. Identify the electrophilic species in the following reaction.

A) H2C=C(CH3)2 B) H2O C) H3O+ D) (CH3)3COH Ans: C

47. Which of the following is the key intermediate in the Markovnikov addition of HBr to

1-butene?




18

48. Which reagent(s) below would convert 2-methyl-2-pentene to 2-methyl-2-pentanol (shown below)?

A) (1) O3 (2) Zn, H2O C) Br2/H2O B) (1) BH3/THF (2) H2O2, NaOH D) H2O/H2SO4 (cat.)

Ans: D

49. What product results from this reaction?

Cl2

H2O

?

CH3

Cl

OH

CH3

OH

Cl

Cl

OH

CH3

A B C D

CH3

Cl

OH


50. Which of the alcohols below could NOT be prepared using hydroboration/oxidation of

an alkene?

OH

OH

OH

OH

AB

CD




19

51. Which brief statement most accurately describes why alkenes react the way they do? A) C=C double bonds are weak. B) a π bond is lost but a stronger σ bond is gained. C) C=C double bonds are unstable. D) C=C π bonds are attacked by nucleophiles.

Ans: B

52. What major product would you expect from this reaction?

C

C

H

C

CH3

CH3

CH3

H

H

H2O

cat. H2SO4

?

A) 3,3-dimethyl-2-butanol C) 2,3-dimethyl-2-butanol B) 3,3-dimethyl-1-butanol D) 2,2-dimethyl-3-butanol

Ans: C


C

H3C

H3C

C C

H3C

H3C

CH3

CH3O2

O

C C

H3C

H3C

CH3

CH3

H OH

C C

H3C

H3C

CH3

CH3

HO OH

AB

C D




20


1. O3

2. Zn or Me2S

?

OH

OH

OH

OH

O

O

O

A B

C D


55. How many of these reagents cause only syn additions to alkenes?

HBr H2, catalyst BH3

Br2CH3CO3H

A) 1 B) 2 C) 3 D) 4 Ans: C

56. What reagents would be required to accomplish the conversion shown below?

CH3

Br

CH3

Br

make into

A) NaOCH3, then Br2 and light. C) NaOCH3, then HBr. B) KOCH3, then HBr and peroxides. D) KOtBu, then Br2 and light.

Ans: B



21

57. The polymerization of styrene gives a polymer that has which structure?

styrene

Ph Ph Ph

Ph Ph

Ph Ph Phn

Ph Ph

n

Ph Ph

n

A. B.

C. D. none of these


Chapter 7 Stereochemistry: Answers Prof. Sivaguru Jayaraman


1

Chapter 7: Stereochemistry 1. Which of the molecules below are chiral?

A) only II B) only III C) I and III D) II and III Ans: D

2. Which of the molecules below are chiral?

A) only I B) I and III C) II and III D) I, II, and III Ans: B

3. Identify the chiral compound(s) below.

A) only II B) II and III C) III and IV D) I, II, and IV Ans: A



2

4. Which of the following molecules are chiral?

A) only II B) only III C) II and III D) I, II, and III Ans: A

5. How many stereogenic centers are there in the following molecule?

A) only 1 B) two C) three D) four Ans: B

6. How many stereogenic centers are there in the following molecule?

A) only 1 B) two C) three D) four Ans: C

7. Give the configurations, respectively, of the following two molecules.

A) R and R B) R and S C) S and S D) S and R Ans: B



3

8. Give the configurations, respectively, of the following two molecules.

A) R and R B) R and S C) S and S D) S and R Ans: A

9. Which one of the following groups has the highest rank as assigned by the Cahn-Ingold-

Prelog system for stereogenic carbons? A) –CH=CH2 B) –CH2OH C) –CH=O D) –CH2SH Ans: D

10. 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 R Ans: B


A) (2S, 3S)-2,3-dibromopentane C) (2R, 3S)-2,3-dibromopentane B) (2S, 3R)-2,3-dibromopentane D) (2R, 3R)-2,3-dibromopentane

Ans: D

12. 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 III Ans: D



4

13. What is the relationship between the following two molecules?

A) identical B) enantiomers C) diastereomers D) constitutional isomers Ans: A

14. What are the configurations of carbons 2 and 3 in the Fischer projection below?

A) 2R, 3R B) 2R, 3S C) 2S, 3R D) 2S, 3S Ans: D

15. Compound X, C5H10O, is optically active. The compound consumes one equivalent of

hydrogen to give C5H12O. The hydrogenation product is also optically active. Which compound below matches the information?


16. A pure sample of (S)-phenylalanine has a specific rotation of +70°. A mixture of the two

enantiomers of phenylalanine has a specific rotation of +7.0°. What are the percentages of the S and R enantiomers in the mixture? A) 95% S, 5% R C) 55% S, 45% R B) 90% S, 10% R D) 52.5% S, 47.5% R

Ans: C



5

17. How many stereoisomers are there for the compound shown below?

A) two B) four C) six D) eight Ans: A

18. Give the total number of stereoisomers of 2,3-dibromobutane.

A) none, only a single structure B) two C) three D) four Ans: C

19. What is the relationship between the following two compounds?

A) identical B) enantiomers C) diastereomers D) constitutional isomers Ans: D


A) different conformations of the same compound B) enantiomers C) diastereomers D) constitutional isomers

Ans: C

21. (+)–Tartaric acid has a specific rotation of +12.0°. What is the specific rotation of a mixture of 75% (+)–tartaric acid and 25% (–)–tartaric acid?

A) +4.0° B) +6.0° C) +8.0° D) +9.0° Ans: B

22. The addition of bromine, Br2, to trans-2-butene gives

A) (2R,3R)-2,3-dibromobutane. B) (2S,3S)-2,3-dibromobutane. C) a racemic mixture of (2R,3R) and (2S,3S)-2,3-dibromobutane. D) meso-2,3-dibromobutane.

Ans: D



6


A) identical B) enantiomers C) diastereomers D) constitutional isomers Ans: B

24. In terms of stereochemistry, the following reaction gives

A) a single enantiomer. C) a nonracemic pair of enantiomers. B) a racemic pair of enantiomers. D) two diastereomers.

Ans: D

25. Which of the following has a meso stereoisomer? I. 2,4-dichloropentane II. 1,3-dimethylcyclopentane III. 2,3-dichloropentane

A) only I B) only II C) I and III D) I and II Ans: D



7

26. 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 III Ans: D

27. Which of the following C6H10 cycloalkenes would give a pair of diastereomeric

epoxides when reacted with peroxyacetic acid, CH3CO3H? A) 1-methylcyclopentene C) 1,2-dimethylcyclobutene B) 3-methylcyclopentene D) 3,3-dimethylcyclobutene

Ans: B

28. The addition of HBr to 1-octene gives A) 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: A

29. Compound X, C6H10, is optically active. Hydrogenation of the compound gives methylcyclopentane. Which compound below is compound X?




8

30. Which of the following is the best method to make a racemic mixture of (+) and (–)–2,3-dibromobutane? A) photochemical bromination of 2-bromobutane B) addition of HBr to racemic 3-bromo-2-butene C) addition of Br2 to cis-2-butene D) addition of Br2 to trans-2-butene

Ans: C

31. Which of the following compounds gives a pair of diastereomers upon epoxidation with peroxyacetic acid, CH3CO3H?


32. How many stereoisomers are there of D-fructose (including D-fructose), shown below?

A) four B) six C) eight D) twelve Ans: C



9

33. Which of the following Fischer projections corresponds to the compound shown below?


34. The four isomeric dimethylcyclopropanes are shown below. Identify two of the isomers

which are related as diastereomers.

A) I and III B) I and IV C) II and III D) III and IV Ans: C

35. How many stereoisomers are there of 1-isopropyl-4-methylcyclohexane?

A) only 1 structure possible - no stereoisomers B) two C) three D) four Ans: B

36. Which object below is achiral?

A) golf club (wood driver) B) baseball glove C) tennis shoe D) baseball bat Ans: D

37. Which compound below has a meso form?

A) 1,2-dichlorobutane C) 2,3-dichlorobutane B) 1,3-dichlorobutane D) 1,4-dichlorobutane

Ans: C



10

38. Which compound below has no stereoisomers? A) 1,2-dichlorobutane C) 2,3-dichlorobutane B) 1,3-dichlorobutane D) 1,4-dichlorobutane

Ans: D

39. Compound X (C7H12) is optically active. Hydrogenation of compound X gives two isomeric 1,2-dimethylcyclopentanes, one is optically active and the other is optically inactive. Of the following compounds, which is the only one that fits the data?


40. Which sawhorse drawing below has the identical conformation as the following Fischer

projection?




11

41. Which one of the following is a diastereomer of (R)-4-bromo-cis-2-hexene? A) (S)-4-bromo-cis-2-hexene C) (R)-4-bromo-trans-2-hexene B) (R)-5-bromo-cis-2-hexene D) (S)-5-bromo-trans-2-hexene

Ans: C

42. Which of the following statements is false? A) Racemic mixtures are optically inactive. B) Enantiomers have specific rotations which are equal, but have opposite signs. C) Achiral molecules are optically inactive. D) Meso compounds contain equal amounts of enantiomers.

Ans: D

43. Which reaction below gives a single enantiomer of a chiral product?




12

44. Which reaction below gives a pair of diastereomers?


45. Which one of the following isomeric dibromobutanes is shown below?

A) (2R, 3R)-2,3-dibromobutane C) meso-2,3-dibromobutane B) (2S, 3S)-2,3-dibromobutane D) (R)-1,2-dibromobutane

Ans: C



13

46. The following isomer of dibromohexane can be synthesized by

A) addition of Br2 to trans-3-hexene. C) addition of HBr to trans-3-hexene. B) addition of Br2 to cis-3-hexene. D) addition of HBr to cis-3-hexene.

Ans: A

47. 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: B

48. Which one of the following is a diastereomer of (2R,3R)-2,3-dibromopentane?

A) (2S,3S)-2,3-dibromopentane C) R-1,2-dibromopentane B) (2S,3R)-2,3-dibromopentane D) (2R,4R)-2,4-dibromopentane

Ans: B

49. Which of the following is the enantiomer of (2R,3R)-2,3-dibromopentane? A) (2S,3S)-2,3-dibromopentane C) (2R,3S)-2,3-dibromopentane B) (2S,3R)-2,3-dibromopentane D) (2R,4R)-2,4-dibromopentane

Ans: A



14

50. What is the IUPAC name of the following hydrocarbon?

A) (R)-4-ethylpentanane C) (S)-2-ethylpentane B) (S)-3-methylhexane D) (R)-3-methylhexane

Ans: B

51. What is the total number of stereoisomers (including the one shown) for the following alcohol?

A) zero (none are possible) B) two C) three D) four Ans: B

52. 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: D

53. Which one of the isomeric C4H9Cl molecules is chiral? A) 1-chlorobutane C) 1-chloro-2-methylpropane B) 2-chlorobutane D) 2-chloro-2-methylpropane

Ans: B



15

54. Which of the following molecules is(are) chiral?

A) only I B) I and II C) II and III D) I, II, and III Ans: A

55. How many stereoisomers of 2,3-pentanediol are possible?

OH

OH

A) 2 B) 3 C) 4 D) 6 Ans: C

56. How many stereoisomers are possible for this structure?

OH

A) 1 B) 4 C) 8 D) 16 Ans: C

57. How many stereoisomers of 2,4-pentanediol are possible?

OHHO

A) 2 B) 3 C) 4 D) 6 Ans: C



16

58. The tartaric acid found in fruits, when isolated, exhibits [α] = +12°. Which configuration is NOT possible for this naturally-occurring material?

CO2HHO2C

HO OH

tartaric acid

A) R,R B) R,S C) S,S D) there is no way to tell Ans: B

59. Which statement would be true of this reaction?

Br2

lightCH3CH2CH2CH3 CH3CH2CHBrCH3

A) 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: B

60. The most specific description of the relationship between the following two molecules is:

C

CH3CH2

Br

CH3H

C

Br

CH2CH3

H

H3C

and

A) identical B) isomers C) enantiomers D) diastereomers Ans: A

61. What are the R/S assignments in this molecule? (assume the carbons are numbered as

shown)

HO2C

CO2H

OH

OH

2

3

A) 2S, 3R B) 2S, 3S C) 2R, 3S D) 2R, 3R Ans: B



17

62. What is the most important reason that chiral drugs are typically sold as single enantiomers? A) one enantiomer is typically a more effective drug B) one enantiomer is typically cheaper to make C) racemic mixtures have already been patented D) one enantiomer is typically easier to separate

Ans: A

63. The free-radical bromination of (R)-2-chlorobutane could produce how many mono-bromo 2-chlorobutanes? (count all isomers that could be formed, including stereoisomers)

ClH

Br2

light?

only (R)

A) four B) five C) six D) eight Ans: C

64. (-)-Fenchone can be purchased in 70% optical purity. What ratio of enantiomers is

present?

O A) 70% (-) : 30% (+) C) 55% (-) : 45% (+) B) 85% (-) : 15% (+) D) 60% (-) : 40% (+)

Ans: B

65. One stereoisomer of the structure below is a poison found in a certain mushroom. How many stereoisomers of this structure are possible?

O

HO

H3C

N(CH3)3

A) 4 B) 8 C) 16 D) 32 Ans: B



18

66. How many chiral centers are present in histrionicotoxin?

A) 2 B) 3 C) 4 D) 5 Ans: C

67. How many chiral centers are in this molecule?

O

HO

HN

CH3

HO

morphine

A) 2 B) 4 C) 5 D) 6 Ans: C

Chapter 8 Nucleophilic Substitution: Answers Prof. Sivaguru Jayaraman


1

Chapter 8: Nucleophilic Substitution 1. Identify the nucleophile in the following reaction.

A) CH3Br B) OH¯ C) H2O D) Br¯ Ans: B

2. Identify the leaving group in the following reaction.

A) CH3CH2Br B) HS¯ C) Br¯ D) CH3OH Ans: C

3. Which of the following cannot act as a nucleophile?

A) NH3 B) H2O C) I¯ D) CH4 Ans: D

4. In the SN2 reaction, the "2" stands for

A) two reactants in the reaction. C) two intermediates in the reaction. B) two steps in the reaction. D) bimolecular kinetics for the reaction.

Ans: D

5. Which of the following undergoes a substitution reaction with sodium cyanide in DMSO at the fastest rate?

A) CH3CH2F B) CH3CH2Cl C) CH3CH2Br D) CH3CH2I Ans: D

6. 1-Chloro-4-fluorobutane is reacted with one equivalent of sodium iodide in acetone.

During the reaction a precipitate forms. What is the precipitate? A) FCH2CH2CH2CH2I B) ClCH2CH2CH2CH2I C) NaCl D) NaF Ans: C

7. The rate law for the following reaction is

A) rate = k[CH3CH2CH2Cl]. C) rate = k[CH3CH2CH2Cl][NaCN]2. B) rate = k[CH3CH2CH2Cl][NaCN]. D) rate = k[NaCN].

Ans: B



2

8. Which of the following reacts the fastest by the SN2 mechanism? A) CH3Br B) CH3CH2Br C) (CH3)2CHBr D) (CH3)3CBr Ans: A

9. Give the product(s) of the following reaction?

A) A B) B C) C D) a mixture of A and B Ans: B

10. Which halide ion reacts the fastest with cyclopentyl p-toluenesulfonate in

ethanol/water?




3

11. Which one of the following species forms the strongest ion-dipole attraction with 18-crown-6?

A) F- B) K+ C) Cr2O7

2- D) Br2 Ans: B

12. Identify the major product(s) in the reaction of (R)-2-bromopentane with sodium

cyanide in DMSO? A) (R)-2-cyanopentane C) racemic mixture of 2-cyanopentane B) (S)-2-cyanopentane D) trans-2-pentene

Ans: B

13. Which of the following reacts fastest with methanol by the SN1 mechanism?


14. A pentacoordinate carbon is a transition state in the _____ mechanism.

A) SN1 B) SN2 C) E1 D) E2 Ans: B



4

15. What is the leaving group in the following reaction?

A) OH- B) H2O C) CH3CH2

+ D) C1- Ans: B

16. Considering the SN1, SN2, E1, and E2 mechanisms, the energy diagram shown below

corresponds to

A) only the SN1 mechanism. C) both the SN1 and E1 mechanisms. B) only the SN2 mechanism. D) both the SN2 and E2 mechanisms.

Ans: D

17. Which of the following is the rate law for the SN1 mechanism of an alkyl halide with a nucleophile? A) rate = k[alkyl halide] C) rate = k[alkyl halide][nucleophile] B) rate = k[nucleophile] D) rate = k[alkyl halide]2[nucleophile]

Ans: A

18. Which of the following bases works best to maximize the E2 product in the reaction shown below?

A) KOCH2CH3 B) NaOCH2CH3 C) NaOC(CH3)3 D) NaOH Ans: C

19. Which of the following does not correctly describe SN2 reactions of alkyl halides?

A) Tertiary halides react faster than secondary halides. B) Rate of reaction depends on the concentrations of both the alkyl halide and the

nucleophile. C) The mechanism consists of a single step with no intermediates. D) The transition state species has a pentavalent carbon atom.

Ans: A



5

20. Identify the substitution product(s) in the following reaction.

A) A B) B C) C D) a mixture of A and B Ans: D



6



22. Starting with 1-hexene, which synthetic sequence below gives 2-cyanohexane?

A) (1) H2SO4 (cat.), H2O (2) NaCN B) (1) HBr/peroxide (2) NaCN C) (1) HBr (2) NaCN D) (1) Br2, H2O (2) NaCN

Ans: C



7

23. Which sequence of reactions below gives the highest yield of ethyl isopropyl ether?


24. In the solvolysis of t-butyl chloride, a minor product is 2-methylpropene, which results

from the:

A) E2 mechanism with OH¯ acting as the base. B) E2 mechanism with H2O acting as the base. C) E1 mechanism with OH¯ acting as the base. D) E1 mechanism with H2O acting as the base.

Ans: D

25. What is the rate limiting step in the following reaction?




8

26. The mechanism of the following reaction is

A) SN1. B) SN2. C) E1. D) E2. Ans: B

27. Which of the following reacts the slowest with sodium cyanide, NaCN?


28. How would you synthesize the following compound starting with optically pure (R) or

(S)-2-butanol?

A) (1) (R)-2-butanol + TsCl (2) NaCN/DMSO B) (1) (S)-2-butanol + TsCl (2) NaCN/DMSO C) (1) (S)-2-butanol + H2SO4 (heat) (2) HBr (3) NaCN/DMSO D) (R)-2-butanol + NaCN/DMSO

Ans: A



9

29. Starting with optically pure (R) or (S)-2-butanol which method below would give the best yield of the following ether?

A) (1) (R)-2-butanol + TsCl (2) CH3ONa B) (1) (S)-2-butanol + TsCl (2) CH3ONa C) (1) (R)-2-butanol + Na (2) CH3I D) (1) (S)-2-butanol + Na (2) CH3I

Ans: D

30. Which of the following conditions favor the SN1 mechanism as opposed to the SN2 mechanism? I. tertiary alkyl halide II. primary alkyl halide III. polar solvent

A) only I B) only II C) I and III D) II and III Ans: C

31. The species shown below represents the transition state for the

A) reaction of 1-propanol with HBr. B) reaction of 1-bromopropane with OH–. C) elimination of HBr from 1-bromopropane. D) addition of HBr to propene with peroxides.

Ans: B

32. The species shown below represents the transition state for the

A) reaction of 1-propanol with HBr. B) reaction of 1-bromopropane with OH–. C) addition of HOBr to 1-propene. D) addition of HBr to propene with peroxides.

Ans: A



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33. Which of the following is the double substitution product of the reaction below?




11

34. Starting with 1-methylcyclohexene, which of the following reaction sequences is the best synthesis of the azide shown below?


35. Rank the following in decreasing order of leaving group ability.

A) I > III > IV > II C) III > II > I > IV B) I > III > II > IV D) II > I > III > IV

Ans: B

36. Identify the mechanistic pathways, respectively, for the products in the following reaction.

A) E1, SN1 B) E1, SN2 C) E2, SN1 D) E2, SN2 Ans: D



12

37. Identify the mechanistic pathways, respectively, for the products in the following reaction.

A) E1, SN1 B) E1, SN2 C) E2, SN1 D) E2, SN2 Ans: A

38. What is the major product in the following reaction?




13

39. Which of the following mechanistic steps is the most likely route for the formation of the cyclic ether shown?


40. In which of the solvents below would the reaction shown take place at the fastest rate?

A) ethanol B) acetic acid C) dimethyl sulfoxide D) water Ans: C

41. Consider the reaction of each of the following with 1-bromopentane. Which one would

have the highest elimination/substitution ratio? A) NaOCH2CH3, ethanol, 55oC C) KOC(CH3)3, (CH3)3COH, 55oC B) NaSH, ethanol-water, 25oC D) KCN, DMSO, 40oC

Ans: C



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42. Which one of the following correctly describes the reaction below?


43. Which of the following undergoes SN1 solvolysis in ethanol/water at the fastest rate?


44. The major product of the following reaction is an alcohol. Which of the following best

describes this reaction?

A) SN2 with inversion of configuration C) SN1 with inversion of configuration B) SN2 with racemization D) SN1 with racemization

Ans: D



15

45. What reagent would you choose to get the best yield of this product?

A) CH3ONa B) CH3CH2OK C) (CH3)2CHONa D) (CH3)3COK Ans: D

46. The major product(s) of this reaction would be

BrH

CH3OH

?(R) only

A) only (R) B) only (S) C) (R) and (S) D) achiral Ans: C


BrH

CH3SNa?(R) only

A) only (R) B) only (S) C) (R) and (S) D) achiral Ans: B


BrH

CH3ONa?(R) only

A) only (R) B) only (S) C) (R) and (S) D) achiral Ans: D

49. Which mechanism is least important for reactions of alkyl halides and sulfonates?

A) SN1 B) SN2 C) E1 D) E2 Ans: C



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50. The major product expected from the reaction below would be

CH3

BrNaCN

CH3OH

?

CH3

CN

CH3

OCH3

CH3 CH2

A B DC A) A B) B C) C D) D Ans: C

51. What major product, if any, is expected here?

I

CH3 CH3OH

?

cis + trans

C

OCH3

CH3 CH3

CH3

OCH3

A B

D: no reaction occurs

cis + trans


Chapter 9 Alkynes: Answers Prof. Sivaguru Jayaraman


1

Chapter 9: Alkynes 1. What is the IUPAC name of the following compound?

A) 5-propyl-3-heptyne C) 5-ethyl-3-octyne B) 5-isopropyl-3-heptyne D) 4-ethyl-5-octyne

Ans: C

2. Which of the following describes the orbital overlap of the C(1) - C(2) sigma bond of 1-butyne, shown below?

A) sp-sp B) sp2-sp2 C) sp3-sp3 D) 2p-2p Ans: A

3. Which of the following gives only one organic product on ozonolysis?

A) 2-hexyne B) 3-hexyne C) 2-heptyne D) 3-heptyne Ans: B


A) 2-methyl-5-propyl-3-heptyne C) 5-ethyl-2-methyl-3-octyne B) 1-isopropyl-3-propyl-1-pentyne D) 4-ethyl-7-methyl-5-octyne

Ans: C

5. Which one of the following describes the C(2)-C(3) sigma bond in the structure below?

A) sp-sp B) sp2-sp2 C) sp3-sp3 D) 2p-2p Ans: A

6. Select the best base to quantitatively remove a proton from acetylene.

A) NaNH2 B) NH3 C) NaOH D) NaOCH2CH3 Ans: A



2

7. Arrange the following in order of decreasing base strength (strongest base first).

A) IV > III > II > I C) I > II > IV > III B) II > III > I > IV D) II > III > IV > I

Ans: D

8. Predict the major product(s) in the reactions below.

A) 1-nonyne B) 2-nonyne C) cis-2-nonene D) trans-2-nonene Ans: B

9. Which one of the following alkynes gives a single ketone in the acid-catalyzed

hydration of each? A) 2-decyne B) 3-decyne C) 4-decyne D) 5-decyne Ans: D

10. Which sequence of reactions works best in synthesizing cis-3-nonene?


11. Which sequence of reactions below works best in carrying out the following

conversion?

A) (1) HBr (2) excess NaNH2 B) (1) Br2 (2) excess NaNH2 C) (1) Br2, H2O (2) excess NaNH2 D) (1) H2O, H2SO4(cat.) (2) excess NaNH2

Ans: B



3

12. Which of the following is the enol intermediate in the acid-catalyzed addition of water to propyne?


13. Which reagent below would be used to convert 2-pentyne to trans-2-pentene?

A) NaNH2, NH3 B) Na, NH3 C) H2, Lindlar Pd D) H2O, HgSO4/H2SO4 Ans: B



4

14. Select the best method to carry out the following conversion.


15. Which of the following is the correct IUPAC name of the product for the reaction

shown below?

A) cis-2-methyl-5-heptene C) cis-6-methyl-2-heptene B) trans-2-methyl-5-heptene D) trans-6-methyl-2-heptene

Ans: D

16. Identify compound Y.

A) 2-bromobutane B) meso-2,3-dibromobutane C) racemic (2R,3R) and (2S,3S)-2,3-dibromobutane D) 2,3-dibromo-2-butene

Ans: C

17. When a terminal alkyne is treated with sodium amide, NaNH2, in liquid ammonia, sodium amide acts as a

A) Brønsted acid. B) Brønsted base. C) reducing agent. D) catalyst. Ans: B

18. When alkynes are treated with sodium metal, Na, in liquid ammonia, sodium acts as a

A) Brønsted acid. B) Brønsted base. C) reducing agent. D) catalyst. Ans: C



5

19. Select the best reaction sequence to make the following ketone.


20. Predict the major product of the following reaction.


21. What is the product of the following reaction sequence?

A) 1-hexanol B) 2-hexanol C) 1,2-hexanediol D) 1-hexene Ans: A



6

22. Rank the following anions in order of increasing base strength.

A) I < II < III B) II < III < I C) III < II < I D) III < I < II Ans: C

23. The larger acid dissociation constant, Ka, of acetylene as compared to ethylene is

primarily attributed to the A) greater electronegativity of an sp carbon as compared to an sp2 carbon. B) smaller electronegativity of an sp carbon as compared to an sp2 carbon. C) acetylide anion being resonance stabilized. D) the 4 π electrons of the acetylide anion stabilizing the negative charge.

Ans: A

24. How would you carry out the following conversion?


25. What is the major product of the reaction shown below?

A) 1,1-dichlorobutane C) 2,2-dichlorobutane B) 1,2-dichlorobutane D) 1,12,2-tetrachlorobutane

Ans: C

26. Why can't methanol, CH3OH, be used as a solvent for sodium amide, NaNH2? A) Sodium amide is nonpolar and methanol is polar. B) Sodium amide is polar and methanol is nonpolar. C) Sodium amide does an acid-base reaction with methanol. D) There would be no ion-dipole attractive forces between the two compounds.

Ans: C

27. Which of the following gives only one organic product on acid-catalyzed hydrolysis? A) 2-hexyne B) 3-hexyne C) 2-heptyne D) 3-heptyne Ans: B



7

28. Ozonolysis of an alkyne gave the two compounds shown below. What is the IUPAC name of the original alkyne? CH3CH2CH2CO2H and (CH3)3CCO2H A) 2,2-dimethyl-3-octyne C) 2,2-dimethyl-3-heptyne B) 3,3-dimethyl-4-octyne D) 6,6-dimethyl-3-heptyne

Ans: C

29. Which of the following reagents would be used to convert 2-pentyne to cis-2-pentene? A) NaNH2, NH3 B) Na, NH3 C) H2, Lindlar Pd D) H2O, HgSO4/H2SO4 Ans: C

30. Hydration of an alkyne, C6H10, gave two ketones in approximately equal amounts.

Which of the following alkynes would be expected to give these results? A) 1-hexyne B) 2-hexyne C) 3-hexyne D) 3,3-dimethyl-1-butyne Ans: B

31. Which of the following ketones cannot be made by the acid-catalyzed hydration of an

alkyne?


32. What is the relationship between the keto and enol forms of acetone?

A) resonance structure C) conformations B) diastereomers D) constitutional isomers

Ans: D

33. Predict the product of the following reaction.

A) 1-bromo-1-chlorocyclopentane C) 1-bromocyclopentene B) 1-bromo-2-chlorocyclopentane D) cyclopentene

Ans: A



8


A) 3-methylhexane C) 3-methyl-1-hexyne B) 2-bromo-3-methylhexane D) 1-bromo-3-methylhexane

Ans: C

35. Is the proposed synthesis of cyclohexanone below likely to work? If not, why not?

A) Yes, it would work. B) No, you would need to start with 1,2-dibromocyclohexane. C) No, cyclohexyne will not form. D) No, the enol of cyclohexanone cannot be formed from cyclohexyne.

Ans: C

36. It is believed that the trans alkenyl radical, shown below, is an intermediate in the sodium metal reduction of an alkyne. Based on this information, the unpaired electron would be located in which of the following orbitals?

A) sp B) sp2 C) sp3 D) 2p Ans: B



9

37. What is the major product of the reaction shown below?


38. What base is able to efficiently (completely) form alkynyl anions from terminal

alkynes?

A) KOtBu B) NaNH2 C) NaOH D) CH3ONa Ans: B

39. What major product do you expect from this reaction?




10

40. How many organic products do you expect from this reaction?

H2O

cat. H2SO4

cat. HgSO4

CH3 ?

A) one B) two C) three D) four Ans: B

41. What major product results from this reaction?

O3

H2O

?

CO2H

CO2H

O

O

O

AB

C D A) A B) B C) C D) D Ans: C

42. What would the name of this molecule be?

A) 2,3-dimethyl-4-hexyne C) 4,5,5-trimethyl-2-pentyne B) 3-isopropyl-2-butyne D) 4,5-dimethyl-2-hexyne

Ans: D



11

43. The product of this reaction would be

C

CH3

C

H

H

only (S)

H2

Pt

?

A) only (S) B) only (R) C) (R) + (S) D) achiral Ans: D

44. The product of this reaction would be

A) only (S) B) only (R) C) (R) + (S) D) achiral Ans: A

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