The College at Old Westbury

ORGANIC 9

Chapter 9: Alkynes

1)What is the IUPAC name of the following compound?

1. 1. 5-propyl-3-heptyne                                           C)         5-ethyl-3-octyne
   2. 5-isopropyl-3-heptyne                                     D)        4-ethyl-5-octyne

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

1. 1. sp-sp      B) sp²-sp²       C) sp³-sp³       D) 2p-2p

3. Which of the following gives only one organic product on ozonolysis?
   1. 2-hexyne      B) 3-hexyne       C) 2-heptyne       D) 3-heptyne

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

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

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

1. 1. sp-sp      B) sp²-sp²       C) sp³-sp³       D) 2p-2p

6. Select the best base to quantitatively remove a proton from acetylene.
   1. NaNH₂       B) NH₃        C) NaOH        D) NaOCH₂CH₃

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

1. 1. IV > III > II > I                                                         C)         I > II > IV > III
   2. II > III > I > IV                                                         D)        II > III > IV > I

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

1. 1. 1-nonyne      B) 2-nonyne       C) cis-2-nonene       D) trans-2-nonene

9. Which one of the following alkynes gives a single ketone in the acid-catalyzed hydration of each?
   1. 2-decyne      B) 3-decyne       C) 4-decyne       D) 5-decyne

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

1. 1. A      B) B       C) C        D) D

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

1. 1. (1) HBr                                   (2) excess NaNH₂
   2. (1) Br₂                                     (2) excess NaNH₂
   3. (1) Br₂, H₂O                          (2) excess NaNH₂
   4. (1) H₂O, H₂SO₄(cat.)           (2) excess NaNH₂

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

1. 1. A      B) B       C) C        D) D

13. Which reagent below would be used to convert 2-pentyne to trans-2-pentene?
    1. NaNH₂, NH₃         B) Na, NH₃         C) H₂, Lindlar Pd           D) H₂O, HgSO₄/H₂SO₄

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

1. 1. A      B) B       C) C        D) D

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

1. 1. cis-2-methyl-5-heptene                                   C)         cis-6-methyl-2-heptene
   2. trans-2-methyl-5-heptene                             D)        trans-6-methyl-2-heptene

16. Identify compound Y.

1. 1. 2-bromobutane
   2. meso-2,3-dibromobutane
   3. racemic (2R,3R) and (2S,3S)-2,3-dibromobutane
   4. 2,3-dibromo-2-butene

17. When a terminal alkyne is treated with sodium amide, NaNH₂, in liquid ammonia, sodium amide acts as a
    1. Brønsted acid.       B) Brønsted base.       C) reducing agent.        D) catalyst.

18. When alkynes are treated with sodium metal, Na, in liquid ammonia, sodium acts as a
    1. Brønsted acid.       B) Brønsted base.       C) reducing agent.        D) catalyst.

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

1. 1. A      B) B       C) C        D) D

20. Predict the major product of the following reaction.

1. 1. A      B) B       C) C        D) D

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

1. 1. 1-hexanol      B) 2-hexanol        C) 1,2-hexanediol        D) 1-hexene

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

1. 1. I < II < III          B) II < III < I           C) III < II < I           D) III < I < II

23. The larger acid dissociation constant, K_a, of acetylene as compared to ethylene is primarily attributed to the
    1. greater electronegativity of an sp carbon as compared to an sp² carbon.
    2. smaller electronegativity of an sp carbon as compared to an sp² carbon.
    3. acetylide anion being resonance stabilized.
    4. the 4 ? electrons of the acetylide anion stabilizing the negative charge.

24. How would you carry out the following conversion?

1. 1. A      B) B       C) C        D) D

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

1. 1. 1,1-dichlorobutane                                            C)         2,2-dichlorobutane
   2. 1,2-dichlorobutane                                            D)        1,12,2-tetrachlorobutane

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

27. Which of the following gives only one organic product on acid-catalyzed hydrolysis?
    1. 2-hexyne      B) 3-hexyne       C) 2-heptyne       D) 3-heptyne

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28. Ozonolysis of an alkyne gave the two compounds shown below. What is the IUPAC name of the original alkyne?

CH₃CH₂CH₂CO₂H and (CH₃)₃CCO₂H

1. 1. 2,2-dimethyl-3-octyne                                      C)         2,2-dimethyl-3-heptyne
   2. 3,3-dimethyl-4-octyne                                      D)        6,6-dimethyl-3-heptyne

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

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?
    1. 1-hexyne      B) 2-hexyne       C) 3-hexyne       D) 3,3-dimethyl-1-butyne

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

1. 1. A      B) B       C) C        D) D

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

1. 1. resonance structure                                          C)         conformations
   2. diastereomers                                                     D)        constitutional isomers

33. Predict the product of the following reaction.

1. 1. 1-bromo-1-chlorocyclopentane                    C)         1-bromocyclopentene
   2. 1-bromo-2-chlorocyclopentane                    D)        cyclopentene

34. What is the product of the following reaction?

1. 1. 3-methylhexane                                                 C)         3-methyl-1-hexyne
   2. 2-bromo-3-methylhexane                              D)        1-bromo-3-methylhexane

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

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

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?

1. 1. sp     B) sp²       C) sp³       D) 2p

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

1. 1. A      B) B       C) C        D) D

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

1. 1. KO^tBu        B) NaNH₂         C) NaOH         D) CH₃ONa

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

1. 1. A      B) B       C) C        D) D

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

1. 1. one     B) two       C) three      D) four

41. What major product results from this reaction?

O

O

A                                                             B

CO2H                                                          O

CO2H

C                                                               D

A) A        B) B       C) C        D) D

42. What would the name of this molecule be?

1. 1. 2,3-dimethyl-4-hexyne                                    C)         4,5,5-trimethyl-2-pentyne
   2. 3-isopropyl-2-butyne                                        D)        4,5-dimethyl-2-hexyne

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