Deck 3: Alkenes and Alkynes

Question 1

Which of the following isomers of C₇H₁₄ do you expect to be most stable?

A)
B)
C)
D)
E)

Answer 1

Question 2

What is the approximate value of the indicated bond angle in the following structure?

A) 60°
B) 90°
C) 109.5°
D) 120°
E) 180°

Answer 2

120°

Question 3

Which alkene is the least stable?

A)
B)
C)
D)
E)

Answer 3

Question 4

How many signals do you expect to see in the ¹³C NMR spectrum of the structure shown?

A) 1
B) 3
C) 4
D) 5
E) 10

Question 5

How many σ and π antibonding molecular orbitals are there in acetylene?

A) 2 σ*, 1 π*
B) 3 σ*, 1 π*
C) 3 σ*, 2 π *
D) 1 σ*, 3 π*
E) 1 σ*, 4 π*

Question 6

How many σ bonds and how many π bonds are in ethylene, C₂H₄?

A) 4 σ bonds and 1 π bond
B) 4 σ bonds and 2 π bonds
C) 5 σ bonds and 1 π bond
D) 1 σ bond and 1 π bond
E) 2 σ bonds and 5 π bonds

Question 7

What atomic orbitals are involved in the formation of the σ bond between the two carbons indicated in this structure?

A) C sp² and C sp²
B) C sp² and C sp³
C) C sp³ and C sp³
D) C p and C p
E) C p and C sp³

Question 8

Which of the following structures is allyl alcohol?

A)

B)
C)
D)
E)

Question 9

Which of the following structures is vinyl bromide?

A)
B)
C)
D)
E)

Question 10

According to Bredt's rule, which of the following cycloalkenes is unlikely to exist?

A)
B)
C)
D)
E)

Question 11

Which of the following structures correctly represents trans-3-heptene?

A)
B)
C)
D)
E)

Question 12

How many σ bonds and how many π bonds are present in propyne?

A) 2 σ bonds, 1 π bond
B) 5 σ bonds, 2 π bonds
C) 6 σ bonds, 2 π bonds
D) 7 σ bonds, 1 π bond
E) 7 σ bonds, 2 π bonds

Question 13

What is the indicated bond angle in the following structure?

A) 60°
B) 90°
C) 109.5°
D) 120°
E) 180°

Question 14

Which of these compounds would you expect to be stable?

A) A
B) B
C) C
D) D
E) None of these

Question 15

Which of the following structures represents a trans alkene?

A)

B)
C)
D)
E)

Question 16

Which of the following structures is properly designated as a Z alkene?

A)
B)
C)
D)
E)

Question 17

Which conformational equilibrium would you expect to be slow at room temperature?

A)
B)
C)
D)
E)

Question 18

Which of the following structures is properly designated as an E alkene?

A)
B)
C)
D)
E)

Question 19

Which set of atomic orbitals could be used to make an sp² hybrid on carbon?

A) C 2 p_z , C 2 p_x and C 2 p_y
B) H 1s, C 2 p_y, and C 2 p_x
C) C 2 s, 2 p_y , and C 2 p_z
D) C 1 s , C 2 p_y, and C 2 p_z
E) C 2 s , H 2 p_x and C 2 p_z

Question 20

How many σ bonds and how many π bonds are in the following structure?

A) 2 σ bonds and 4 π bonds
B) 4 σ bonds and 2 π bonds
C) 7 σ bonds and 2 π bonds
D) 8 σ bonds and 2 π bonds
E) 12 σ bonds and 2π bonds

Question 21

In the first step of the reaction between HBr and 2-methylpropene shown here, identify the HOMO and the LUMO.

A) HOMO} is C-C π, is H-Br σ.
B) HOMO is C-C π, LUMO is H-Br σ*.
C) HOMO is C-C σ, LUMO is H-Br σ.
D) HOMO is C-C π * , LUMO is H-Br σ.
E) HOMO is H-Br σ and LUMO is C-C π .

Question 22

Question 23

What is the major product of the reaction shown here?

A)
B)
C)
D)
E)

Question 24

Draw all geometric isomers of 2-methyl-3-hexene.

Question 25

Which of the following choices is the correct name for the structure shown here?

A) 4-methylhept- (E)-2 -en-5-yne
B) 4-methylhept-(Z)-2-en-5-yne
C) 4-methylhept- (E)-5
D) 4-methylhept-(Z)-5-en-2-yne
E) 4-methylheptyne-en-2-yne

Question 26

Which of the following is the most stable carbocation?

A)
B)
C)
D)
E) All arecequaly sable.

Question 27

Provide an acceptable IUPAC name for the structure shown here.

Question 28

Calculate the degree of unsaturation for a compound with molecular formula C₉H₁₄BrCl.

A) 0
B) 1
C) 2
D) 3
E) Not enough information is given to answer the question.

Question 29

Draw a line structure for trans-4-methyl-2-pentene.

Question 30

For ethylene, C₂H₄, indicate the hybridization of each carbon atom in the molecule, the types of bonds each carbon forms, the orbitals involved in forming each of these bonds, and all bond angles.

Question 31

Question 32

Which molecule would not have an unsaturation number of 5?

A)
B)
C)
D)
E)

Question 33

Which of these bases can deprotonate acetylene (pKa 26)? The pKa values for the conjugate acids are shown in parentheses.

A) NaOH(15.7)
B) Butyllithium (50-60)
C) NaNH2(36)
D) NaHCO3(6.3)
E) Both b and c

Question 34

How many signals do you expect to find in the ¹H NMR and ¹³C NMR spectra for the following molecule?

A) 2 signals in the ¹H NMR and 3 signals in the ¹³C NMR
B) 3 signals in the ¹H NMR and 3 signals in the ¹³C NMR
C) 3 signals in the ¹H NMR and 4 signals in the ¹³ C NMR
D) 5 signals in the ¹H NMR and 5 signals in the ¹³ C NMR
E) 8 signals in the ¹H NMR and 5 signals in the ¹³ C NMR

Question 35

Which reaction is the most endothermic?

A)
B)
C)
D)
E)

Question 36

Which of the following is the most stable carbocation?

A)
B)
C)
D)
E)

Question 37

Which of the following is the most acidic hydrocarbon?

A)
B)
C)
D)
E)

Question 38

Which of the following compounds do not have three degrees of unsaturation?

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

Question 39

Which of the following is a tertiary carbocation?

A)
B)
C)
D)
E)

Question 40

What is the major product of the reaction shown here?

A)
B)
C)
D)
E)

Question 41

Using E and Z nomenclature where necessary, draw and name all alkene isomers with the formula C₆H₁₂ that can be named as pentenes.

Question 42

How many degrees of unsaturation are there in this compound?

Question 43

Estimate the energy change for the reaction shown here.

Question 44

Draw two possible alkene starting materials that would give the product shown here when treated with HCl.

Question 45

Draw the structure of 2-methyl-3-hexyne.

Question 46

Explain why small and medium cycloalkenes are much more stable as cis isomers than as trans
isomers.

Question 47

Draw the structure that results from the mechanistic step shown here.

Question 48

Calculate the degree of unsaturation and draw six constitutional isomers for the molecular formula C₈H₁₂.

Question 49

Draw the product of the following reaction.

Question 50

What is the product of the following reaction?

Question 51

Arrange in order of acidity (most acidic to least acidic):

Question 52

Question 53

Question 54

Predict the product of the following reaction and draw a mechanism to account for its formation.
Include all curved arrows, lone pairs of electrons, and nonzero formal charges.

Question 55

At room temperature, cis and trans alkene isomers do not equilibrate; that is, they do not interconvert.Explain why.

Question 56

Name the orbitals that overlap to form each of the indicated bonds in propyne.

Question 57

Place the following alkene isomers in order of increasing stability and indicate which of them has the most negative value for ΔH_f°.

Question 58

Is the mechanistic step shown here endothermic or exothermic? Explain your answer briefly.

Question 59

Draw the structure of (Z)-4, 7-dimethyloct-2-en-5-yne.

Question 60

Describe all possible combinations of structural units consistent with an unsaturation number of 4.

Question 61

Write a reaction mechanism for the following reaction.

Question 62

Provide the product for the reaction below.

Question 63

What is the LUMO in the mechanistic step shown here?

Question 64

Draw a reaction coordinate diagram, including the structures of any intermediates, illustrating the
competing reaction pathways below.Indicate the key energy difference on the diagram that makes
path b the predominant one (that is, the one that gives the major product).

Question 65

Provide an alkene starting material for the reaction below.

Question 66

Predict the reaction product, and provide a mechanism for its formation.

Question 67

Which carbocation is the most stable?

Question 68

Predict the product of the following reaction and draw a mechanism to account for its formation.
Include all curved arrows, lone pairs of electrons, and nonzero formal charges.

Question 69

Predict the reaction product.

Question 70

Predict the reaction product, and write a mechanism for its formation.