Organic Chemistry Wade Test Bank

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Organic Chemistry, 7e (Wade) Chapter 9 Alkynes

1) How many distinct alkynes exist with a molecular formula of C4H6? A) 0 B) 1 C) 2 D) 3 E) 4 Answer: C Diff: 1 Section: 9.2

2) How many distinct alkynes exist with a molecular formula of C4H8? A) 0 B) 1 C) 2 D) 3 E) 4 Answer: A Diff: 1 Section: 9.2

3) How many distinct terminal alkynes exist with a molecular formula of C5H8? A) 1 B) 2 C) 3 D) 4 E) 5 Answer: B Diff: 2 Section: 9.2

4) How many distinct internal alkynes exist with a molecular formula of C6H10? A) 1 B) 2 C) 3 D) 4 E) 5 Answer: C Diff: 2 Section: 9.2

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5) The correct IUPAC name for the following structure is __________. A) (Z) 4-isopropyl-4-hepten-2-yne B) (E) 4-isopropyl-3-hepten-5-yne C) (E) 4-isopropyl-4-hepten-2-yne D) (Z) 4-isopropyl-3-hepten-5-yne Answer: C Diff: 3 Section: 9.2

6) What is the correct IUPAC name for the following compound?

A) 4-(1-bromopropyl)-1-hexen-5-yne B) 4-allyl-5-bromo-1-hexyne C) 3-(1-bromopropyl)-5-hexen-1-yne D) 5-bromo-4-ethynyl-1-heptene Answer: C Diff: 3 Section: 9.2

7) Give the IUPAC name for Cl3CCH2CH2CH2C≡CH. Answer: 6,6,6-trichlorohex-1-yne

Diff: 2 Section: 9.2

8) Provide the IUPAC name for the compound below.

Answer: 3-ethylhex-4-yn-3-ol Diff: 2

Section: 9.2

9) Provide the IUPAC name for Cl3C(CH2)3C≡CH.

Answer: 6,6,6-trichloro-1-hexyne or 6,6,6-trichlorohex-1-yne Diff: 2

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10) Provide the IUPAC name for (CH3)2CHCH2CH(OH)CH2C≡CCH3. Answer: 2-methyl-6-octyn-4-ol or 2-methyloct-6-yn-4-ol

11) Name the compound shown below.

Answer: 6,6-dimethyl-3-heptyne or 6,6-dimethylhept-3-yne Diff: 2

Section: 9.2

12) Draw and name all terminal alkynes with molecular formula C5H8.

Answer: CH3CH2CH2C≡CH, 1-pentyne or pent-1-yne; (CH3)2CHC≡CH, 3-methyl-1-butyne or 3-methylbut-1-yne

13) Give the IUPAC name for HC≡CCH2CH2CH3. Answer: pent-1-yne

14) Draw an acceptable structure for acetylene. Answer: H–C≡C–H

15) Draw an acceptable structure for hex- 2-yne. Answer:

16) Give the IUPAC name for (CH3)2C(CH2CH3)C≡CCH(CH3)2. Answer: 2,5,5-trimethylhept-3-yne

17) Give the IUPAC name for CH3CH2C≡CCH(OH)CH3. Answer: hex-3-yn-2-ol

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18) Give the IUPAC name for BrCH2CH2C≡CCH2CH3. Answer: 1-bromohex-3-yne

19) Draw an acceptable structure for 3-sec-butylhept-1-yne. Answer:

20) Draw an acceptable structure for (S)-5-phenyloct-2-yne. Answer:

21) Draw an acceptable structure for hepta-3,6-dien-1-yne. Answer: HC≡CCH=CHCH2CH=CH2

22) Give the IUPAC name for CH3CH=CHCH=CHC≡CCH3. Answer: octa-2,4-dien-6-yne

23) Which of the following improperly describes the physical properties of an alkyne? A) relatively nonpolar

B) nearly insoluble in water C) less dense than water

D) insoluble in most organic solvents

E) boiling point nearly the same as an alkane with similar carbon skeleton Answer: D

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24) Which of the following alkynes has the lowest boiling point? A) 3,3-dimethyl-1-butyne B) 1-hexyne C) 2-hexyne D) 3-hexyne E) 1-decyne Answer: A Diff: 2 Section: 9.3

25) How many moles of oxygen are required in the complete combustion of 1 mole of acetylene? A) 1 B) 1.5 C) 2 D) 2.5 E) 3 Answer: D Diff: 2 Section: 9.4

26) What products result when calcium carbide is combined with water? Answer: acetylene and calcium hydroxide

27) How many moles of water are produced when one mole of propyne undergoes complete combustion?

Answer: two Diff: 2 Section: 9.4

28) The carbon-carbon triple bond of an alkyne is composed of __________. A) three σ bonds

B) three π bonds

C) two σ bonds and one π bond D) one σ bond and two π bonds Answer: D

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29) In trans-hept-4-en-2-yne the shortest carbon-carbon bond is between carbons __________. A) 1 and 2 B) 2 and 3 C) 3 and 4 D) 4 and 5 E) 6 and 7 Answer: B Diff: 1 Section: 9.5

30) Circle the shortest bond in the compound below.

Answer:

31) Which of the species below is less basic than acetylide? A) CH3Li

B) CH3ONa C) CH3MgBr D) both A and C E) all of the above Answer: B

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32) Among the compounds water, but-1-yne, but-2-yne, and ethane, which are stronger acids than ammonia?

A) but-1-yne and ethane B) water and but-1-yne C) water and ethane

D) but-1-yne and but-2-yne Answer: B

33) To a solution of propyne in diethyl ether, one molar equivalent of CH3Li was added and the resulting mixture was stirred for 0.5 hour. After this time, an excess of D2O was added.

Describe the major organic product(s) of this reaction. A) CH3C≡CD + CH4 B) CH3C≡CCH3 C) CD3C≡CD3 D) CH3C≡CCD3 E) CH3C≡CD + CH3D Answer: A Diff: 2 Section: 9.6

34) Which of the following bases are sufficiently strong to deprotonate a terminal alkyne with an equilibrium constant greater than 1?

1) sodium methoxide 3) n-butyl lithium

2) lithium diisopropyl amide 4) phenylmagnesium bromide A) 1, 2, and 3 B) 2, 3 and 4 C) 2 and 3 D) 3 and 4 E) 1, 2, 3 and 4 Answer: B Diff: 3 Section: 9.6

35) Explain why the synthetic route shown below would be unsuccessful.

H C  - Na+ C: _{H3CH2C–C≡C–CH2CH3} 3. CH3CH2I

Answer: Sodium methoxide is not a sufficiently strong base to deprotonate the intermediate terminal alkyne.

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36) Provide the major organic product of the reaction below.

Answer: (CH3)2CHCH2CH2C≡CD Diff: 2

Section: 9.6

37) Why are terminal alkynes more acidic then other hydrocarbons?

Answer: The carbanion which results upon deprotonation of a terminal alkyne has the lone pair of electrons in an sp hybrid orbital. The greater % s character of this orbital gives this orbital a significantly lower energy.

38) Provide the structure of the major organic product(s) in the reaction below.

Answer:

39) Describe a qualitative, nonspectroscopic means for distinguishing terminal alkynes from internal ones.

Answer: Add a solution of Cu+ or Ag+. Terminal alkynes react to form insoluble metal acetylides which precipate.

40) Explain why the synthetic route shown below would be unsuccessful.

H C  - Na+ C: _{(H3C)3C–C≡C–CH2CH3} 3. (CH3)3CBr

Answer: The tert-butyl bromide would not undergo SN2 when treated with the intermediate alkynide because the steric hinderance in the halide is too great. Instead, the alkynide would deprotonate the tertiary bromide via an E2 mechanism.

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41) Provide the major organic product of the reaction shown below.

Answer:

42) What's the problem with the synthetic approach shown below?

Answer: The bromide is tertiary and therefore too hindered to undergo SN2. An E2 reaction would occur instead.

43) Name the product which results when CH3C≡CLi reacts with CH3CH2COCH2CH3 followed by addition of water.

Answer: 3-ethylhex-4-yn-3-ol Diff: 3

Section: 9.7

44) What conditions could be used to isomerize hept-2-yne to hept-1-yne? Answer:

1. NaNH2, 150°C 2. H2O

45) Complete the short synthesis below by providing the necessary reagents.

Answer: 1) Br2 2) CH3C≡CNa 3) Na / NH3 Diff: 3

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46) Provide the structure of the major organic product(s) in the reaction sequence below. CH3CH2CCH 2 2 1. NaNH 2. PhCH Br → Answer: CH3CH2CCCH2Ph Diff: 1 Section: 9.7

47) Describe a sequence of reactions by which hept-3-yne can be straightforwardly prepared from acetylene. Answer: 1. NaNH2 2. CH3CH2Br 3. NaNH2 4. CH3CH2CH2Br Diff: 1 Section: 9.7

48) Describe a sequence of reactions by which butylbenzene can be straightforwardly prepared from phenylacetylene. Answer: 1. NaNH2 2. CH3CH2Br 3. H2, Pt Diff: 1 Section: 9.7

49) 2-Methylhex-3-yne can be prepared by the reaction of an alkynide with an alkyl halide. Does the better synthesis involve alkynide attack on bromoethane or on 2-bromopropane? Explain your reasoning.

Answer: Attack on the primary bromide (bromoethane) is much more favorable. Reaction of an alkynide with the secondary bromide would result mostly in elimination instead of substitution. Diff: 2

Section: 9.7

Answer:

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Answer:

52) Provide the structure of the major organic product(s) in the reaction sequence below.

Answer:

53) Describe a sequence of reactions by which 1-propylcyclohexan-1-ol can be straightforwardly prepared from propyne.

Answer: 1. NaNH2 2. cyclohexanone 3. H+, H2O 4. H2, Pt Diff: 2 Section: 9.7

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54) Describe a sequence of reactions by which the compound shown below can be straightforwardly prepared from acetylene.

Answer: 1. NaNH2 2. CH3CH2Br 3. NaNH2 4. cyclopentanone 5. H+, H2O Diff: 2 Section: 9.7

55) Describe a sequence of reactions by which (E)-5-bromopent-2-ene can be straightforwardly prepared from propyne.

Answer: 1. NaNH2

2. ethylene oxide (oxirane) 3. H+, H2O

4. Na, NH3 5. PBr3 Diff: 3 Section: 9.7

56) Why is a terminal alkyne favored when sodium amide (NaNH2) is used in a elmination reaction with 2,3-dichlorohexane?

A) The strong base deprotonates the terminal alkyne and removes it from the equilibrium. B) The resonance favors the formation of the terminal rather than internal alkyne.

C) The positions of the Cl atoms induce the net formation of the terminal alkyne.

D) The terminal alkyne is more stable than the internal alkyne and is naturally the favored product.

E) The terminal alkyne is not favored in this reaction. Answer: A

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57) When 2,2-dibromobutane is heated at 200°C in the presence of molten KOH, what is the major organic product?

A) 1-bromobut-1-yne B) 1-bromobut-2-yne C) but-1-yne D) but-2-yne E) but-1-ene Answer: D Diff: 3 Section: 9.8

Answer: CH3(CH2)5C≡CH Diff: 2

Section: 9.8

59) Describe a sequence of reactions by which hept-1-yne can be straightforwardly prepared from hept-1-ene. Answer: 1. Br2 2. NaNH2, heat Diff: 3 Section: 9.8

60) Which of the following describes an unsymmetrical addition reaction? A) propyne with 1 mole H2, Ni and heat

B) propyne with 2 moles Cl2 in CCl4 C) propyne with 1 mole Br2 in CCl4 D) propyne with Na/NH3

E) propyne with 1 mole HBr Answer: E

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61) Which of the follwing reagents will convert 1 mole of methylpent-1-yne into 3-methylpentane?

A) 1 mole of Br2 in CCl4 B) 2 moles of Cl2 in CCl4 C) 2 moles of HCl

D) 2 moles H2, Ni and heat E) 1 mole H2, Ni and heat Answer: D

62) A mixture of hept-1-yne, hept-2-yne, and hept-3-yne was hydrogenated in the presence of a platinum catalyst until hydrogen uptake ceased. If one assumes that the hydrogenation went to completion, how many different seven-carbon hydrocarbons were produced?

A) 1 B) 2 C) 3 D) 6 E) 8 Answer: A Diff: 2 Section: 9.9

63) __________ is produced when 1 equivalent of HBr is added to hex-1-yne in the presence of peroxides.

A) 2-Bromohex-1-ene B) E-1-Bromohex-1-ene C) Z-1-Bromohex-1-ene

D) A mixture of E and Z isomers of 1-bromohex-1-ene E) E-2-Bromohex-2-ene

Answer: D Diff: 2 Section: 9.9

64) Which of the alkyne addition reactions below involve(s) an enol intermediate? A) hydroboration/oxidation

B) treatment with HgSO4 in dilute H2SO4 C) hydrogenation

D) both A and B E) none of the above Answer: D

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65) Which of the following reagents should be used to convert hex-3-yne to (E)-hex-3-ene? A) H2, Pt B) Na, NH3 C) H2, Lindlar's catalyst D) H2SO4, H2O E) HgSO4, H2O Answer: B Diff: 2 Section: 9.9

66) Which of the following reagents should be used to convert hex-3-yne to (Z)-hex-3-ene? A) H2, Pt B) Na, NH3 C) H2, Lindlar's catalyst D) H2SO4, H2O E) HgSO4, H2O Answer: C Diff: 2 Section: 9.9

67) What is the major organic product that results when 3-heptyne is hydrogenated in the presence of Lindlar's catalyst?

A) 2-heptyne B) (Z)-2-heptene C) (Z)-3-heptene D) (E)-3-heptene E) heptane Answer: C Diff: 2 Section: 9.9

68) What is the major organic product that results when 3-heptyne is subjected to excess hydrogen and a platinum catalyst?

A) 2-heptyne B) (Z)-2-heptene C) (Z)-3-heptene D) (E)-3-heptene E) heptane Answer: E Diff: 2 Section: 9.9

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69) What is the major organic product that results when 3-heptyne is treated with sodium metal in ammonia? A) 2-heptyne B) (Z)-2-heptene C) (Z)-3-heptene D) (E)-3-heptene E) heptane Answer: D Diff: 2 Section: 9.9

70) What is the major organic product that results when 1-heptyne is treated with 2 equivalents of HBr? A) 2,3-dibromo-1-heptene B) 2,3-dibromo-2-heptene C) 1,2-dibromoheptane D) 2,2-dibromoheptane E) 1,1-dibromoheptane Answer: D Diff: 2 Section: 9.9

71) What class of organic product results when 1-heptyne is treated with a mixture of mercuric acetate in aqueous sulfuric acid?

A) aldehyde B) ketone C) diol D) ether E) carboxylic acid Answer: B Diff: 2 Section: 9.9

72) What class of organic product results when 1-heptyne is reacted with disiamylborane followed by treatment with basic hydrogen peroxide?

A) aldehyde B) ketone C) diol D) ether E) carboxylic acid Answer: A Diff: 2 Section: 9.9

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73) What major organic product results when 3-octyne is treated with sodium metal in liquid ammonia? A) (E)-3-octene B) (Z)-3-octene C) 1-octyne D) 1-octene E) octane Answer: A Diff: 2 Section: 9.9

74) What is the major product of the following acid/catalyzed hydration reaction?

A) B) C) D) E) Answer: C Diff: 3 Section: 9.9

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75) In the reduction of alkynes using sodium in liquid ammonia, which of the species below is not thought to be an intermediate in the commonly accepted mechanism?

A) vinyl anion B) vinyl radical C) radical anion D) vinyl cation Answer: D Diff: 3 Section: 9.9

76) In the addition of hydrogen bromide to alkynes in the absence of peroxides, which of the following species is thought to be an intermediate?

A) vinyl anion B) vinyl cation C) vinyl radical D) carbene

E) none of the above Answer: B

77) Complete the transformation below by indicating the necessary sequence of reagents.

A) 1) DBr _{2) BD3} _{3) H2O2 / NaOH}

B) 1) D2 / Pd, BaSO4, quinoline 2) Br2 / H2O

C) 1) Na / ND3 2) Br2 3) H2O

D) 1) Na / ND3 2) Br2 / H2O

E) 1) Br2 / H2O 2) D2 / Pd, BaSO4, quinoline Answer: B

78) Name the compound which results when pent-2-yne is subjected to catalytic hydrogenation using a platinum catalyst.

Answer: pentane Diff: 1

Section: 9.9

79) Name the compound which results when pent-1-yne is treated with sodium in liquid ammonia.

Answer: pent-1-ene Diff: 2

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Answer:

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Answer:

Answer: (CH3)2CHCH2CH2CH2CH3 Diff: 2

Section: 9.9

Answer: (CH3)2CHCH2CH2CH=CH2 Diff: 2

Section: 9.9

Answer: (CH3)2CHCH2CH2CH2CHO Diff: 2

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86) Complete the following reaction sequences below by filling-in the missing reagents or structures.

Answer:

87) Complete the synthesis below by providing all necessary reagents and show all intermediate structures.

Answer: 1) NaNH2, 2) bromoethane, 3) Na / NH3 Diff: 3

Section: 9.9

88) Treatment of hex-2-yne with mercuric sulfate in dilute sulfuric acid yields a mixture of two ketones. Similar treatment of hex-3-yne produces a single ketone instead of a mixture. Explain. Answer: The two carbons of the triple bond in hex-3-yne are equivalent, and only 3-hexanone results. In the case of hex-2-yne, the two carbons of the triple bond are not equivalent, and a mixture of 2- and 3-hexanone results.

89) Describe a sequence of reactions by which trans-pent-2-ene can be straightforwardly prepared from propyne.

Answer: 1. NaNH2 2. CH3CH2Br 3. Na, NH3 Diff: 1 Section: 9.9

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Answer:

Ph–C≡C–Ph 2 4 D Pd/BaSO , quinoline → Answer: Diff: 2 Section: 9.9

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94) Describe a sequence of reactions by which racemic 2,3-dibromobutane can be straightforwardly prepared from propyne.

Answer: 1. NaNH2 2. CH3I 3. H2, Lindlar's catalyst 4. Br2, CCl4 Diff: 2 Section: 9.9

95) Describe a sequence of reactions by which hexan-2-ol can be straightforwardly prepared from hex-1-yne.

Answer:

1. HgSO4, H2O, H2SO4 2. NaBH4

Answer:

97) Provide the structure of the major organic product(s) in the reaction sequence below.

Answer:

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98) Describe a sequence of reactions by which meso-2,3-dibromobutane can be straightforwardly prepared from propyne.

Answer: 1. NaNH2 2. CH3Br 3. Na, NH3 4. Br2, CCl4 Diff: 3 Section: 9.9

99) Describe a sequence of reactions by which meso-hexane-3,4-diol can be straightforwardly prepared from hex-3-yne.

Answer:

1. H2, Lindlar's catalyst

2. OsO4, H2O2 or cold, dilute KMnO4, -OH or 1. Na, NH3 2. PhCO3H 3. H3O+ or -OH Diff: 3 Section: 9.9

100) Describe a sequence of reactions by which (Z)-hex-3-en-1-ol can be straightforwardly prepared from but-1-yne.

Answer: 1. NaNH2

2. ethylene oxide (oxirane) 3. H+, H2O

4. H2, Lindlar's catalyst Diff: 3

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101) Describe a sequence of reactions by which the compound shown below can be straightforwardly prepared from acetylene.

Answer: 1. NaNH2 2. CH3I 3. NaNH2 4. CH3I 5. Na, NH3 6. PhCO3H Diff: 3 Section: 9.9

102) Which of the following reagents should be used to convert an internal alkyne to an α-diketone?

A) KMnO4, H2O, neutral B) O3 then H2O

C) Sia2BH then H2O2 D) Na, NH3

E) HgSO4, H2SO4 Answer: A

Diff: 2

Section: 9.10

103) What two organic compounds result when 3-heptyne is heated in basic aqueous KMnO4? Answer: CH3CH2CO2- and

CH3CH2CH2CO2-Diff: 2

Section: 9.10

104) What two organic compounds result when 3-heptyne is treated with ozone followed by hydrolysis?

Answer: CH3CH2CO2H and CH3CH2CH2CO2H Diff: 2

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105) Predict the necessary starting material for the reaction below.

Answer: 3-methyl-2-hepten-5-yne Diff: 3

Section: 9.10

106) Provide the structure of the major organic product(s) in the reaction below. CH3CH2CH2CH2CH2–C≡C–CH2CH3 3

2 1. O 2. H O → Answer: CH3CH2CH2CH2CH2CO2H + CH3CH2CO2H Diff: 2

Section: 9.10

107) Draw the products which result when oct-3-yne is heated in basic potassium permanganate solution.

Answer: CH3CH2CO2- K+ + CH3CH2CH2CH2CO2- K+ Diff: 2

Section: 9.10

108) Describe a sequence of reactions by which CH3CH2CH2COCH2CH3 can be straightforwardly prepared from but-1-yne.

Answer: 1. NaNH2 2. CH3CH2Br

3. HgSO4, H2O, H2SO4 Diff: 2

Section: 9.10

Answer:

Diff: 3