Chapter 9 Flashcards by Allison Krause

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

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

C) 2

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

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

A) 0

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

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

B) 2

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

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

C) 3

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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

D) insoluble in most organic solvents

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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

A) 3,3-dimethyl-1-butyne

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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

B) shorter, weaker

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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

D) 2.5

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What products result when calcium carbide is combined with water?

acetylene and calcium hydroxide

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

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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

D) one σ bond and two π bonds

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32) 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

B) 2 and 3

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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

B) CH3ONa

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35) 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

B) water and but-1-yne

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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

A) CH3CCD + CH4

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What is the pKa of a terminal alkyne?

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

D) 25

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Why are terminal alkynes more acidic then other hydrocarbons?

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.

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)

A, B, and D

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

B) 2, 3 and 4

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

3-ethylhex-4-yn-3-ol

63) 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.

A) The strong base deprotonates the terminal alkyne and removes it from the equilibrium.

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

D) but-2-yne

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

E) propyne with 1 mole HBr

69) 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

D) 2 moles H2, Ni and heat

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

pentane

72) 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 ```

B) Na, NH3

73) 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 ```

C) H2, Lindlar's catalyst

74) 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 ```

A) 1

75) ________ 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 ```

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

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 ```

D) both A and B

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 ```

C) (Z)-3-heptene

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 ```

E) heptane

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 ```

D) (E)-3-heptene

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 ```

D) 2,2-dibromoheptane

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 ```

B) ketone

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 ```

A) aldehyde

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 ```

A) (E)-3-octene

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

pent-1-ene

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

D) vinyl cation

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 ```

B) vinyl cation

Which of the following reagents should be used to convert an internal alkyne to an ``` A) KMnO4, H2O, neutral B) O3 then H2O C) Sia2BH then H2O2 D) Na, NH3 E) HgSO4, H2SO4 ```

A) KMnO4, H2O, neutral

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Chapter 9 Flashcards

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