Deck 10: Electrophilic Additions to Alkenes

Question 1

Which of the following alkenes will be protonated most rapidly by sulfuric acid?

A) A
B) B
C) C
D) D
E) E

Answer 1

D

Question 2

Which of the following cations is allylic?

A)
B)
C)
D)
E)

Answer 2

Question 3

Which of the following statements about the reaction shown here is true?

I. The alkene is a Brønsted base.
II. The alkene is a Brønsted acid.
III. The rate-limiting step is carbocation formation.
IV. The rate-limiting step is nucleophilic attack by chloride ion on a carbocation.

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

Answer 3

I, III

Question 4

Which of the following statements is true about the reaction shown here?

A) The products are diastereomers, formed in unequal amounts.
B) The products are diastereomers, formed in equal amounts.
C) The products are enantiomers, formed in unequal amounts.
D) The products are enantiomers, formed in equal amounts.
E) The products are structural isomers, formed in unequal amounts.

Question 5

Which of the following is the major product of this reaction?

A)
B)
C)
D)
E)

Question 6

Identify the orbitals that are mixing to stabilize the carbocation by hyperconjugation.

A)
B) p and sp³
C) p and sp²
D)
E)

Question 7

Which of these guidelines would not be used for assigning weighting factors for resonance forms?

A)Resonance forms must have the same number of paired and unpaired electrons.
B)Separation of charges is preferred.
C)The more bonds in a resonance form, the more stable the form is.
D)Equivalent resonance forms contribute equally.
E)Delocalization of charge is stabilizing.

Question 8

Which of these products is not the result of Markovnikov addition of HBr to an alkene?

A)
B)
C)
D)
E)

Question 9

What is the LUMO in the first step of the reaction shown here?

A)
B)
C)
D)
E)

Question 10

Which of the following statements about the allyl cation is false? (Refer to the numbering provided in the structure.)

A) There is a node at C 2 of the lowest unoccupied molecular orbital (LUMO).
B) The positive charge equilibriates between C 1 and C3 .
C) The positive charge is shared by C 1 and C 3 .
D) The p-atomic orbitals combine to form three molecular orbitals.
E) There are two electrons in this system.

Question 11

Which of the following statements about the mechanism of the addition shown below is true?

A) The transition state for the rate-determining step resembles the starting materials.
B) The addition of chloride anion occurs in the rate-determining step.
C) The reaction proceeds via a concerted mechanism.
D) The addition of the proton is an endothermic step in the reaction mechanism.
E) The HCl acts as the nucleophile in the addition reaction.

Question 12

What is the HOMO in the first step of the reaction shown here?

A)
B)
C)
D)
E)

Question 13

Which of the following statements about Markovnikov hydration is false?

A)An acid catalyst must be used.
B)A carbocation intermediate is formed in the rate-determining step of the reaction.
C)The OH group in the product is attached to the more substituted carbon of the original alkene.
D)Water acts as a base in the final step of the reaction mechanism.
E)The alkene starting material is protonated by water in the first step of the reaction.

Question 14

Which of the following alkenes will be protonated most rapidly by sulfuric acid?

A) A
B) B
C) C
D) D
E) E

Question 15

Which of these products would not form from the following reaction?

A)

B)

C)

D)

E)

Question 16

Which alkene monomer would react with sulfuric acid to generate the following polymer?

A)

B)

C)

D)

E)

Question 17

Which of the following structures is not a possible product of the reaction shown here?

A)

B)

C)

D)

E)

Question 18

Which of the following is the least likely product of the reaction conditions shown here?

A)
B)
C)
D)
E)

Question 19

Which of the following carbocations is least likely to rearrange?

A) A
B) B
C) C
D) D
E) E

Question 20

Which of the following carbocations is least likely to rearrange?

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

Question 21

Which of the following methods is the correct way to synthesize the product shown from the given starting material?

A) HCl
B) 1 .
2. HCl
C) 1.
2.
3. TsCl , pyridine
4. NaCl
D) 1.
2. TsCl , pyridine
E) The starting material cannot be transformed to the product shown.

Question 22

Which of these processes is a syn addition?

A) Hydration of an alkene using water and catalytic sulfuric acid.
B) Addition of HCI to an alkene.
C) Addition of CI₂ to an alkene.
D) Hydroboration/oxidation of an alkene.
E) Both a and b.

Question 23

Shown here is hydroboration/oxidation reaction of an alkene.

One of the reagents is labeled with 18O . Which of the following choices correctly shows this label?

A)
B)
C)
D) Either b or c .
E) Any of these is correct .

Question 24

Predict the product of the following reaction conditions.

Question 25

Which of these statements about hydroboration is false?

A)Hydroboration is regiospecific.
B)The overall reaction involves the formation of a C-H bond and a C-B bond.
C)The overall reaction involves the formation of a C-B bond and a B-H bond.
D)Boron attaches to the less substituted end of an alkene.
E)The mechanism of hydroboration is believed to be concerted.

Question 26

Identify the HOMO and LUMO in the rate-limiting step of the reaction shown here.

Question 27

Draw a mechanism to account for the formation of the product shown.

Question 28

Which of the following structures is the product of the reaction shown here?

A)
B)
C)
D)
E)

Question 29

Draw the π molecular orbitals of allyl cation in order of increasing energy (lowest energy at the bottom of the diagram). Include all π electrons and all nodes.

Question 30

Draw a mechanism illustrating the formation of the product of the reaction shown here.

Question 31

What is the correct structure of ?

A)
B)
C)
D)
E)

Question 32

Provide the correct name for the major expected addition product formed in the following
reaction.

Question 33

Which of the following statements about borane is true?

A)Borane is stable in its monomeric form.
B)Borane acts as a Lewis acid.
C)Borane forms a stable complex with ethers.
D)Borane adds a proton to a double bond.
E)Double bonds undergo antiaddition with boranes.

Question 34

Name the major addition products formed in this reaction and state their relationships to one
another.

Question 35

Predict the product of the following reaction.

Question 36

Which of these processes is an anti-Markovnikov addition?

A) Hydration of an alkene using water and catalytic nitric acid.
B) Addition of HCI to an alkene.
C) Addition of Br₂ to an alkene.
D) Hydroboration/oxidation of an alkene.
E) Both c and d.

Question 37

Which of the following compounds could not be synthesized from 1,3-dimethylcyclohexene by methods explored in this chapter?

A)
B)
C)
D)
E)

Question 38

Define the term regioselectivity.

Question 39

Which of the following structures could be the product of hydroboration/oxidation of an alkene?

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

Question 40

Which of the following structures could be produced on reaction of two molecules of the starting material shown in acidic conditions?

A)
B)
C)
D)
E)

Question 41

What is the reverse of Markovnikov hydration, and what kind of mechanism is this?

Question 42

Draw the most reasonable resonance structure for the carbocation shown here.Include all lone pairs of
electrons and any nonzero formal charges.

Question 43

Draw all the possible addition products formed in the reaction shown.

Question 44

From slowest to fastest, rank these alkenes in order of their reactivity with hydrogen bromide.
Draw the expected product(s) from each reaction, indicating major and minor products.

Question 45

Using propene as your only carbon source, devise an efficient synthesis of the target molecule.
Show the reagents needed for each step and the product of each step.

Question 46

For the following reactions, indicate what product(s) would be formed.Include correct
stereochemistry when the reaction is stereoselective.

Question 47

Treatment of 1-methylcyclohexene with sulfuric acid and heat leads to a mixture of dimeric alkenes.
Propose a mechanism for the formation of this mixture and indicate the major and minor products.

Question 48

Show the mechanism by which the following reaction occurs.

Question 49

State the basis of Markovnikov's rule.

Question 50

Both of the two isomeric alkenes below react with aqueous sulfuric acid to give
1-phenyl-1-propanol as the major product.Show the mechanism of the reaction in each case.

Question 51

Draw a mechanism to account for the formation of the product of the reaction shown here.

Question 52

Draw and name the product of Markovnikov hydration of the alkene shown here using aqueous
sulfuric acid.

Question 53

Dimerization of 1-methylcyclopentene generates three isomers with molecular formula C₁₂H₂₀.
Draw the three isomers, designate their stereochemistry (E or Z), and indicate the expected
relative amounts (most, middle, least) based on product stability.

Question 54

What is the structure of the most substituted alkene precursor from which the alcohol shown could
be directly synthesized?

Question 55

Propose a mechanism to account for the formation of the observed product.

Question 56

Draw the structures of two alkene precusors from which the alcohol shown here could be made in
a single synthetic step.

Question 57

Draw a mechanism for dimerization of the alkene shown here under acidic conditions.

Question 58

Provide the correct name for the major expected product of the reaction shown here.

Question 59

Show the principal product(s) of the following reactions; include stereochemistry as needed.

Question 60

Draw a mechanism to account for the formation of the product shown here.

Question 61

Design a multistep synthesis of the target molecule from the starting material.You may use any
inorganic or organic reagents necessary.Show the reagents necessary for each step and the
product of each step.

Question 62

Provide the missing structures and reagents in the following reaction sequence.

Question 63

Draw a mechanism for the transformation shown.Include all curved arrows, necessary lone pairs,
and nonzero formal charges.

Question 64

Devise a multistep synthesis of the target molecule from the given starting material.Show the
reagents needed for each step and the product of each step.

Question 65

Devise a multistep synthesis of the target molecule from the given starting material.Show the
reagents needed for each step and the product of each step.

Question 66

Devise a multistep synthesis of the target molecule from the given starting material.Show the
reagents needed for each step and the product of each step.

Question 67

Show the products of the following reactions with correct stereochemistry.

Question 68

Draw the structure of the precursor alkene to this alcohol and indicate the reagents you would use
to convert the precursor to the alcohol.