April 24th, 2002

Dr. S. A. Dandekar

CHEM 2370

Exam 3 (100 points)

Name _________________________

Select the best answer from the given choices for ANY 28 of questions 1-

32. You may do more than the required number of questions if you wish.

1. What is the simplest alkene, i.e., the one with the smallest

molecular weight, which can exhibit optical activity?

a. 3-methyl-1-pentene

b. 3-methyl-2-pentene

c. 4-methyl-1-pentene

d. 3-methyl-1-butene

e. 4-methyl-2-hexene

2. One mol of each of the following alkenes is subjected to complete

combustion. Which would you expect to liberate the least heat?

a. 1-Pentene

b. 2-Pentene

c. 2-Methyl-1-butene

d. 2-Methyl-2-butene

e. 3-Methyl-1-butene

3. Which of the following carbocations would be likely to undergo

rearrangement?

a. CH₃——CH——CH——CH₃

+ |

CH₃

b. CH₃

CH₃——CH——C——CH₃

+ |

CH₃

c. CH₃

CH₃——C——CH₂——CH₃

d. More than one of these

e. All of these

Exam 3 (100 points)--Page 2

4. Which mechanistic step in the acid-catalyzed dehydration of

3,3-dimethyl-2-butanol is the rate determining step?

a. Step 1. CH₃ CH₃

| |

CH₃——C———CH——CH₃ + H₃O⁺ ‹===› CH₃——C———CH——CH₃ + H₂O

| | | |

CH₃ OH CH₃ OH₂

b. Step 2. CH₃ CH₃

| |

CH₃——C———CH——CH₃ ‹===› CH₃——C———CH——CH₃ + H₂O

| | | +

CH₃ OH₂ CH₃

c. Step 3. CH₃ CH₃

| |

CH₃——C——CH——CH₃ ‹===› CH₃——C——CH——CH₃

| + + |

CH₃ CH₃

d. Step 4. CH₃

CH₃——C——CH——CH₃ + H₂O ‹===› (CH₃)₂CC(CH₃)₂ + H₃O⁺

+ |

CH₃

5. Rearrangements are likely to occur in which of the following

reaction types?

a. S_N1 reactions

b. S_N2 reactions

c. E1 reactions

d. E2 reactions

e. Both S_N1 and E1 reactions

6. Which can exist as cis-trans isomers?

a. 1-Pentene

b. 3-Hexene

c. Cyclopentene

d. 2-Methyl-2-butene

e. 3-Ethyl-2-pentene

7. What characteristic(s) of alkynes would make it difficult to prepare

cyclohexyne?

a. the requirement for linearity at the triple bond center

b. the large electron density between carbons of a triple bond

c. the short carbon-carbon triple bond length

d. the need that the carbon-carbon triple bond be internal in the

chain

e. All of these

Exam 3 (100 points)--Page 3

8. On hydrogenation, a compound C₉H₁₂ absorbs 2 mol of hydrogen.

Which of the following is a possible structure for the compound?

a. I

b. II

c. III

d. IV

e. V

9. Which would be the major product of the following reaction?

a. I

b. II

c. III

d. IV

e. V

10. A compound with the formula C₁₀H₁₄ reacts with excess hydrogen

and a catalyst to yield a compound with the formula C₁₀H₁₈. The

compound could have:

a. one ring and three double bonds.

b. two rings and two double bonds.

c. two rings and a triple bond.

d. no rings and two double bonds.

e. More than one of these

Exam 3 (100 points)--Page 4

11. The correct IUPAC name for

H₃C Cl is:

\ /

/ \

Br CH₂CHCH₃

CH₃

a. (E)-2-Bromo-3-chloro-5-methyl-2-hexene

b. (E)-2-Bromo-3-chloro-5-methyl-3-hexene

c. (Z)-2-Bromo-3-chloro-5-methyl-3-hexene

d. (Z)-2-Bromo-3-chloro-5-methyl-2-hexene

e. (E)-2-Methyl-5-bromo-4-chloro-4-hexene

12. Predict the major product.

a. I

b. II

c. III

d. Equal amounts of I and II

e. No E2 reaction will occur.

13. Which alkene would you expect to be the major product of the

following dehydration?

a. I

b. II

c. III

d. IV

e. V
Exam 3 (100 points)--Page 5

14. What product would result from the following reaction?

a. I

b. II

c. III

d. IV

e. V

15. Which alkene would yield only CH₃CH₂COOH on oxidation with hot

alkaline potassium permanganate?

a. H₃C H

\ /

/ \

H CH₂CH₂CH₃

b. H₃C CH₂CH₂CH₃

\ /

/ \

H H

c. H₃C CH₂CH₃

\ /

/ \

H₃C H

d. H₃CH₂C H

\ /

/ \

H CH₂CH₃

e. H₃C H

\ /

/ \

H CH(CH₃)₂

Exam 3 (100 points)--Page 6

16. Which of these is not formed when cyclopentene reacts with an

aqueous solution of bromine?

a. I

b. II

c. III

d. IV

e. V

17. Which reaction is regioselective?

a. I

b. II

c. III

d. IV

e. None of these

18. Select the structure of the major product formed in the following

reaction.

a. I

b. II

c. III

d. IV

e. V

Exam 3 (100 points)--Page 7

19. Which reaction of an alkene proceeds with anti addition?

a. Dissolving metal reduction

b. Bromination

c. Radical catalysed hydrohalogenation

d. Hydrogenation

e. Epoxidation

20. A chain reaction is one that:

a. involves a series of steps.

b. involves two steps of equal activation energy.

c. can be initiated by light.

d. involves a series of steps, each of which generates a reactive

intermediate that brings about the next step.

e. involves free radicals that have an unusual stability and thereby

cause a large quantum yield.

21. The p-orbital of a methyl radical carbon, CH₃, contains how many

electrons?

a. 1

b. 2

c. 3

d. 4

e. 0

22. Which of the following statements is true when used to compare the

reaction of chlorine with isobutane and the reaction of bromine with

isobutane?

a. Bromine is the less reactive and the more selective.

b. Chlorine is the less reactive and the more selective.

c. Chlorine is the more reactive and the more selective.

d. Bromine is the more reactive and the more selective.

e. None of these

23. Select the structure of the major product formed in the following

reaction.

a. I

b. II

c. III

d. IV

e. V

Exam 3 (100 points)--Page 8

24. What would be the major product of the following reaction?

a. I

b. II

c. III

d. IV

e. V

25. In the presence of light, ethane (1 mol) reacts with chlorine

(1 mol) to form which product(s)?

a. CH₂ClCHCl₂

b. CH₃CHCl₂

c. CH₃CH₂Cl

d. ClCH₂CH₂Cl

e. All of these

26. The reaction of 2-methylbutane with chlorine would yield how many

monochloro derivatives (include stereoisomers)?

a. 2

b. 3

c. 4

d. 5

e. 6

27. How many ¹H NMR signals would you expect from this compound?

a. 1

b. 2

c. 3

d. 4

e. 5

Exam 3 (100 points)--Page 9

28. A compound with the molecular formula C₃H₆Cl₂ gave a ¹H NMR spectrum

consisting only of a triplet centered at d 3.7 and a quintet centered

at d 2.2 . The most likely structure for the compound is:

a. CH₃CH₂CHCl₂

b. CH₃CHClCH₂Cl

c. ClCH₂CHClCH₃

d. ClCH₂CH₂CH₂Cl

e. CH₃CCl₂CH₃

29. For the C-2 methylene group in 1-bromopropane,

CH₃——CH₂——CH₂——Br

c b a

the theoretical multiplicity in the ¹H NMR spectrum, presuming that

J_ab is sufficiently different from J_bc and that the instrument has

sufficient resolving power, is which of these?

a. 2

b. 5

c. 6

d. 8

e. 12

30. In the structure shown, H_b and H_c are classified as:

a. homotopic protons.

b. vicinal protons.

c. enantiotopic protons.

d. diastereotopic protons.

e. isomeric protons.

31. Consider the ¹H NMR spectrum of very pure 1-propanol,

CH₃—CH₂—CH₂—OH.

a b c d

Assuming the maximum multiplicity of signals and non-superposition of peaks,

what is the number of peaks to be observed theoretically, in the order:

(a, b, c, d)

a. (3, 6, 4, 1)

b. (3, 6, 4, 3)

c. (3, 12, 3, 1)

d. (3, 12, 3, 3)

e. (3, 12, 6, 3)

Exam 3 (100 points)--Page 10

32. Distinction between the methine protons in the compounds

H Cl

| |

CH₃——C——CH₂CH₃ and CH₃——C——CH₂CH₃

| |

Cl H

should be possible in the ¹H NMR spectra if:

a. a very high field instrument is used.

b. the spectra are determined in a chiral solvent.

c. a long scan time is used for each compound.

d. a high amplitude setting is employed.

e. Distinction between the enantiomers is impossible.

Exam 3 (100 points)--Page 11 April 24th, 2002

ANSWER KEY (a)

Dr. S. A. Dandekar CHEM 2370

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|Chapter| Ref |Question|Answer| Type | Cat | Lvl | Obj | Page |

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| 7 16 1 a M-Choice |

| 7 17 2 d M-Choice |

| 7 20 3 d M-Choice |

| 7 24 4 b M-Choice |

| 7 30 5 e M-Choice |

| 7 33 6 b M-Choice |

| 7 51 7 a M-Choice |

| 7 35 8 d M-Choice |

| 7 41 9 a M-Choice |

| 7 37 10 e M-Choice |

| 7 55 11 e M-Choice |

| 7 57 12 b M-Choice |

| 7 65 13 c M-Choice |

| 8 14 14 c M-Choice |

| 8 16 15 d M-Choice |

| 8 18 16 e M-Choice |

| 8 28 17 a M-Choice |

| 8 32 18 d M-Choice |

| 8 29 19 b M-Choice |

| 10 1 20 d M-Choice |

| 10 4 21 a M-Choice |

| 10 9 22 a M-Choice |

| 10 23 23 b M-Choice |

| 10 27 24 a M-Choice |

| 10 33 25 e M-Choice |

| 10 35 26 e M-Choice |

| 9 26 27 b M-Choice |

| 9 10 28 d M-Choice |

| 9 31 29 e M-Choice |

| 9 36 30 d M-Choice |

| 9 41 31 e M-Choice |

| 9 37 32 b M-Choice |

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