Deck 6: Reactions of Alkenes and Alkynes

Question 1

Identify the true statements pertaining to the mechanism for the acid-catalyzed addition of water to an alkene.

A) The addition of the electrophile is a slow step.
B) The addition of the nucleophile is a fast step.
C) A carbocation is formed as an intermediate.
D) Water removes a proton from the protonated alcohol.
E) All of the above

Answer 1

All of the above

Question 2

What is the major product of the following reaction?

A)
B)
C)
D)
E)

Answer 2

Question 3

What is the major product when 1-hexyne reacts with excess HBr?

A) 1,1 -dibromohexane
B) 1,1-dibromohexene
C) 1,2 -dibromohexene
D) 1,2-dibromohexane
E) 2,2 -dibromohexane

Answer 3

2,2 -dibromohexane

Question 4

What two atomic orbitals overlap to form the carbon-carbon ? bond in ethyne?

A) $s p ^ { 3 } - s p ^ { 3 }$
B) $p - p$
C) $s p ^ { 2 } - s p ^ { 2 }$
D) $S - S$
E) $s p - s p$

Question 5

What is the major product of the following reaction?

A)
B)
C)
D)
E)

Question 6

Which of the following statements is not true about propyne $\mathrm { HC } \equiv \mathrm { C } - \mathrm { CH } _ { 3 }$ ?

A) It contains six sigma bonds.
B) It contains three pi bonds.
C) The $\mathrm { H } - \mathrm { C } - \mathrm { H }$ bond angle is about $109.5 ^ { \circ }$
D) The $\mathrm { C } - \mathrm { C } - \mathrm { C }$ bond angle is $180 ^ { \circ } .$
E) The pi bond is weaker than the sigma bond.

Question 7

How many isomers with molecular formula $\mathrm { C } _ { 6 } \mathrm { H } _ { 10 }$ contain an internal alkyne?

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

Question 8

Which of the following does not describe 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

Question 9

Which of the following statements describes the reactivity of alkynes?

A) An alkyne is an electron-rich molecule and therefore reacts as a nucleophile.
B) The σ bonds of alkynes are greater in energy than the π bonds and, therefore, are more reactive.
C) Unlike alkenes, alkynes fail to undergo electrophilic addition reactions.
D) When a symmetrical internal alkyne reacts with HBr, two products are formed.
E) Alkynes react as electrophiles, whereas alkenes react as nucleophiles.

Question 10

The carbon-carbon triple bond of an alkyne is composed of ________.

A) three $\sigma$ bonds
B) two $\sigma$ bonds and one $\pi$ bond
C) one $\sigma$ bond and two $\pi$ bonds
D) three $\pi$ bonds

Question 11

Which of the following carbocations is likely to rearrange? I.
II.
III.
IV.

A) I
B) II
C) III
D) IV
E) II and IV

Question 12

What is the hybridization of the carbons numbered 1 and 2, respectively?
$\begin{array} { c } \quad\quad\quad\quad\quad\quad1 \quad2\\\mathrm { H } _ { 3 } \mathrm { C } - \mathrm { CH } = \mathrm { CH } - \mathrm { C } \equiv \mathrm { C } - \mathrm { H }\end{array}$

A) $s p ^ { 3 } , s p ^ { 2 }$
B) $s p ^ { 2 } , s p ^ { 2 }$
C) $s p ^ { 2 } , s p$
D) sp, sp

Question 13

What is the major product of the following reaction?
I.

II.

III.

IV.

V.

A) I
B) II
C) III
D) IV
E) V

Question 14

What is the hybridization of the carbons numbered 1 and 2, respectively?

A) $s p ^ { 3 } , s p ^ { 2 }$
B) $s p ^ { 2 } , s p ^ { 2 }$
C) sp, sp
D) $s p ^ { 2 } , s p$
E) $s p , s p^ { 2 }$

Question 15

Which of the following is the most stable carbocation?

A)
B)
C)
D)
E)

Question 16

What is the systematic name of the following compound?

A) 5-bromo-2-heptyne
B) 3-bromo-5-heptyne
C) 2-bromo-2-methyl-4-hexyne
D) 5-bromo-5,5-dimethylhexyne
E) 5-bromo-5-methyl-2-hexyne

Question 17

What is the major product of the following reaction?

A)
B)
C) $\mathrm { CH } _ { 3 } \mathrm { CH } = \mathrm { CH } - \mathrm { Cl }$
D)
E)

Question 18

Which of the following is the most stable carbocation? I.

II.

III.

IV.

V.

A) I
B) II
C) III
D) IV
E) V

Question 19

How many isomers with molecular formula $\mathrm { C } _ { 5 } \mathrm { H } _ { 8 }$ contain a terminal alkyne?

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

Question 20

Which of the following alkenes forms 3-bromo-3-methylpentane as the major product when it reacts with HBr?

A) I and II only
B) III only
C) I, II, and III only
D) all of them
E) none of them

Question 21

Draw the major product of the following reaction:

Question 22

Draw the major product of the following reaction:

Question 23

Which of the following are enol tautomers of the ketone shown below?

A)
B)
C)
D)
E)

Question 24

What is hyperconjugation and how does it affect carbocation stability?

Question 25

Draw the major product of the following reaction:

Question 26

A mixture of 1-heptyne, 2-heptyne, and 3-heptyne was hydrogenated in the presence of a palladium catalyst until hydrogen uptake ceased. How many seven-carbon hydrocarbons were
Produced?

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

Question 27

Explain the reason for the regioselectivity exhibited by the addition of hydrogen halides to an
alkene.

Question 28

Draw the major product of the following reaction:

Question 29

Draw the major product of the following reaction:

Question 30

Draw the major product of the following reaction:

Question 31

What is the major product of the following reaction?

A) $\mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 3 }$
B)
C)
D)
E)

Question 32

What is the major product of the following reaction?

I.

II.

III.

IV.

V.

A) I
B) II
C) III
D) IV
E) V

Question 33

Draw the major product of the following reaction:

Question 34

The reagent needed to convert 2-butyne to cis-2-butene is ________.

A) $\mathrm { H } _ { 2 } , \mathrm { Pd } / \mathrm { C }$
B) $\mathrm { H } _ { 2 } / \text { Lindlar cataly }$
C) $\mathrm { Li } / \mathrm { NH } _ { 3 }$
D) $\mathrm { Na } / \mathrm { NH } _ { 3 }$
E) $\mathrm { H } ^ { + } / \mathrm { H } _ { 2 }$

Question 35

What is the major product of the following reaction?

A) $\mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 3 }$
B)
C)
D)
E)

Question 36

Which is more highly regioselective: the addition of HCl to methylenecyclohexane or to 1-methylcyclohexene? Explain.

Question 37

Draw the major product of the following reaction:

Question 38

Draw the major product of the following reaction:

Question 39

Draw the structures of the two alkenes that react with HBr to form 1-bromo-1-
methylcyclopentane as the major product.

Question 40

What is the major product of the following reaction?

A)
B)
C)
D) $\mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } = \mathrm { CHOH }$
E)

Question 41

Write structures and give systematic names for all alkynes with molecular formula C₅H₈.

Question 42

Draw the major product of the following reaction. The mechanism is the same as the mechanism for the addition of water to an alkene.

Question 43

Draw the major product of the following reaction:

Question 44

Draw the major product of the following reaction:

Question 45

Draw the major product of the following reaction:

Question 46

Draw the major product of the following reaction:

Question 47

Draw the major product of the following reaction:

Question 48

Draw the structure of acetylene.

Question 49

Draw the major product of the following reaction. The mechanism is the same as the mechanism for the addition of water to an alkene.

Question 50

Name

Question 51

Draw the major product of the following reaction:

Question 52

Draw the major product of the following reaction:

Question 53

Propose a mechanism for the following reaction:

Question 54

Draw the major product of the following reaction:

Question 55

Draw the major product of the following reaction. The mechanism is the same as the mechanism for the addition of water to an alkene.

Question 56

Draw the major product of the following reaction:

Question 57

Draw the major product of the following reaction. The mechanism is the same as the mechanism for the addition of water to an alkene.

Question 58

Name

Question 59

Name

Question 60

Draw the structure of all terminal alkynes with molecular formul C₆H₁₀.

Question 61

Draw the major product of the following reaction:

Question 62

Is the equilibrium constant of the following reaction greater than 1 or less than 1?

Question 63

Draw the stereoisomer that is formed when 2-butyne reacts with H₂ in the presence of Lindlar catalyst.

Question 64

Draw the major product of the following reaction:

Question 65

Draw the major product of the following reaction:

Question 66

Draw the major product of the following reaction:

Question 67

Draw the major product that is formed when 2-butyne reacts wit H₂SO₄ in water.

Question 68

Draw 3-sec-butyl-1-heptyne.

Question 69

Draw the major product of the following reaction:

Question 70

Draw the major product of the following reaction:

Question 71

Draw the major product of the following reaction:

Question 72

Draw the major product that is formed when 2-butyne reacts with 2 equivalents of HCl.

Question 73

Draw 2-hexyne.

Question 74

Draw the major product of the following reaction:

Question 75

Draw the major product of the following reaction:

Question 76

Name the following compound:

Question 77

Name the following compound

Question 78

Draw the major product of the following reaction:

Question 79

Draw the major product of the following reaction:

Question 80

Name the following compound: