Deck 9: Alkynes

Question 1

What is the correct IUPAC name for the following structure?

A) (Z) 1-cyclopentyl-3,6-dimethylhept-3-en-1-yne
B) (E) 1-cyclopentyl-3,6-dimethylhept-1-yn-3-ene
C) (Z) 1-cyclopentyl-4,7-dimethylhept-4-en-2-yne
D) (E) 1-cyclopentyl-3,6-dimethylhept-3-en-1-yne

Answer 1

(E) 1-cyclopentyl-3,6-dimethylhept-3-en-1-yne

Question 2

How many distinct internal alkynes exist with a molecular formula of C₆H₁₀?

A) 1
B) 2
C) 3
D) 4
E) 5

Answer 2

3

Question 3

Provide the IUPAC name for the compound below.

Answer 3

3-ethylhex-4-yn-3-ol

Question 4

Draw an acceptable structure for 3-sec-butylhept-1-yne.

Question 5

How many distinct terminal alkynes exist with a molecular formula of C₅H₈?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 6

Name the compound shown below.

Question 7

Give the IUPAC name for BrCH₂CH₂C=CCH₂CH₃.

Question 8

Draw an acceptable structure for hex- 2-yne.

Question 9

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

Question 10

Give the IUPAC name for (CH₃)₂C(CH₂CH₃)C=CCH(CH₃)₂.

Question 11

Provide the IUPAC name for (CH₃)₂CHCH₂CH(OH)CH₂C≡CCH₃.

Question 12

Give the IUPAC name for CH₃CH₂C=CCH(OH)CH₃.

Question 13

How many distinct alkynes exist with a molecular formula of C₄H₈?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 14

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

Question 15

Draw an acceptable structure for hepta-3,6-dien-1-yne.

Question 16

Draw an acceptable structure for acetylene.

Question 17

Draw and name all terminal alkynes with molecular formula C₅H₈.

Question 18

Give the IUPAC name for HC=CCH₂CH₂CH₃.

Question 19

Give the IUPAC name for Cl₃CCH₂CH₂CH₂C≡CH.

Question 20

How many distinct alkynes exist with a molecular formula of C₄H₆?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 21

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

Question 22

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

Question 23

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

Question 24

What is the pKa of a terminal alkyne?

A) 4
B) 10
C) 16
D) 25
E) 44

Question 25

Provide the major organic product of the reaction below.

Question 26

Why are terminal alkynes more acidic then other hydrocarbons?

Question 27

Which of the following $\underline{\text{ improperly }}$ 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

Question 28

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

Question 29

The pi bond of an alkyne is ________ and ________ than the pi bond of an alkene.

A) shorter, stronger
B) shorter, weaker
C) longer, stronger
D) longer, weaker

Question 30

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

Question 31

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

Question 32

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

Question 33

Explain why the synthetic route shown below would be unsuccessful.
H-C≡C:^- Na⁺ H₃CH₂C-C≡C-CH₂CH₃
3. CH₃CH₂I

Question 34

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

Question 35

Circle the shortest bond in the compound below.

Question 36

Provide the IUPAC name for the compound below.

Question 37

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

Question 38

Give the IUPAC name for CH₃CH=CHCH=CHC≡CCH₃

Question 39

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

Question 40

What products result when calcium carbide is combined with water?

Question 41

Provide the structure of the major organic product(s) in the reaction sequence below.
CH₃CH₂C≡CH →

Question 42

Describe a sequence of reactions by which butylbenzene can be straightforwardly prepared from phenylacetylene.

Question 43

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

Question 44

Explain why the synthetic route shown below would be unsuccessful.
H≡C≡C:^-Na⁺

C-C≡C-CH₂CH₃
3. (CH₃)₃CBr

Question 45

Provide a correct structure for the product of the following reaction.

Question 46

Describe a sequence of reactions by which hept-3-yne can be straightforwardly prepared from acetylene.

Question 47

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

Question 48

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

Question 49

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

Question 50

What is the pKa of a terminal alkyne?

A) 4
B) 10
C) 16
D) 25
E) 44

Question 51

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

Question 52

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

Question 53

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

Question 54

What conditions could be used to isomerize hept-2-yne to hept-1-yne?

Question 55

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

Question 56

Which of the following bases will favorably deprotonate a terminal alkyne?
(More than one answer is possible.)

A) n-BuLi
B) LDA
C) NaOMe
D) PhMgBr (Ph=phenyl)

Question 57

Complete the short synthesis below by providing the necessary reagents.

Question 58

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.

Question 59

Provide the major organic product of the reaction shown below.

Question 60

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

Question 61

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

Question 62

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

Question 63

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

Question 64

Describe a sequence of reactions by which hept-1-yne can be straightforwardly prepared from hept-1-ene.

Question 65

________ 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

Question 66

Why is a terminal alkyne favored when sodium amide (NaNH₂) is used in an elimination 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.

Question 67

Which of the following reagents will convert 1 mole of 3-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

Question 68

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

Question 69

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

Question 70

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

Question 71

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

Question 72

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

Question 73

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

Question 74

Provide the major organic product of the reaction below.

Question 75

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

Question 76

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

Question 77

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

Question 78

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.

Question 79

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

Question 80

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 $\underline{\text{ different }}$ seven-carbon hydrocarbons were produced?

A) 1
B) 2
C) 3
D) 6
E) 8