Deck 8: Reactions of Alkenes

Question 1

Explain the regioselectivity observed in the radical addition of HBr to 2-methylpropene.

Answer 1

The reaction proceeds via the addition of Br^∙ to the alkene. Two competing pathways are possible, but the transition state leading to the more substituted alkyl radical is lower in energy. This process ultimately makes the addition anti-Markovnikov in nature.

Question 2

Draw the major regioisomeric product generated in the reaction below.

Answer 2

Question 3

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Answer 3

Question 4

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 5

Based on the relative stabilities of the intermediates involved, explain the basis for Markovinkov's rule in the addition of hydrogen halides to alkenes.

Question 6

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 7

When propylene reacts with hydrogen bromide in the presence of a peroxide initiator, which of the following structures are formed during the mechanism?

A)
B)
C)
D) H∙

Question 8

Name the major product which results when HBr is added to 3-ethyl-3-hexene.

Question 9

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 10

Predict the major product of the following reaction.

A)
B)
C)
D)

Question 11

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 12

Using any alkene as your starting material, how could you make the alkyl halide shown?

Question 13

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 14

Draw a full and complete mechanism to account for the formation of the product in the reaction shown below.

Question 15

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 16

Provide the structure of the major organic product of the reaction below.

Question 17

Provide the structure of the major organic product of the reaction below.

Question 18

Complete the following reaction and provide a detailed, step-by-step mechanism for the process.

Question 19

Provide the major organic product of the reaction below.

Question 20

HBr can be added to an alkene in the presence of peroxides (ROOR). What function does the peroxide serve in this reaction?

A) nucleophile
B) electrophile
C) radical chain initiator
D) acid catalyst
E) solvent

Question 21

The mechanism for the acid-catalyzed hydration of alkenes is simply the reverse of the mechanism by which alcohols are dehydrated using concentrated acid. This is an illustration of the principle of ________.

Question 22

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 23

Provide the reagents necessary to complete the following transformation.

Question 24

When 3,6-dimethylcyclohexene is reacted with dry gaseous HBr, one of the products is 1-bromo-1,4-dimethylcyclohexane. Provide a detailed step-by-step mechanism to explain the formation of this product.

Question 25

What is the major product of the following reaction?

A)
B)
C)
D)

Question 26

What synthetic goal is achieved by subjecting an alkene to an oxymercuration-demercuration sequence?

A) Markovnikov addition of H₂O wherein skeletal rearrangement is promoted
B) Markovnikov addition of H₂O wherein skeletal rearrangement is prevented
C) anti-Markovnikov addition of H₂O wherein skeletal rearrangement is promoted
D) anti-Markovnikov addition of H₂O wherein skeletal rearrangement is prevented
E) syn-hydroxylation

Question 27

Which of the following is the best reaction sequence to use if one wants to accomplish a Markovnikov addition of water to an alkene with minimal skeletal rearrangement?

A) water + dilute acid
B) water + concentrated acid
C) oxymercuration-demercuration
D) hydroboration-oxidation
E) none of the above

Question 28

Which radical is an intermediate in the following reaction?

A)
B)
C)
D)

Question 29

Treatment of an alkene with an alcohol in the presence of an acid catalyst produces an ether as the major organic product. Provide a mechanism that shown how this product is formed.

Question 30

Provide the reagents necessary to complete the following transformation.

A) 1. BH₃^∙THF 2. H₂O₂, HO^-
B) H₂O, H₂SO₄
C) OsO₄, H₂O₂
D) CH₃CO₃H
E) 1. CH₃CO₃H 2. H⁺, H₂O

Question 31

Acid catalyzed hydration (H₂SO₄/water/△) of an unknown compound (A) with a chemical formula C₆H₁₂, yielded a racemic mixture of product C₆H₁₃OH. Which, if any, of the following compounds is/are possible structures for the initial compound (A)?

A) compound 1 only
B) compounds 2 and 3
C) compound 2 only
D) compounds 1 and 3
E) none of the above

Question 32

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 33

Provide the structure of the major organic product of the reaction below.

Question 34

Which of the following intermediates is thought to occur in the mechanism by which alkenes are hydrated in the presence of acid?

A) carbanion
B) carbocation
C) free radical
D) carbene
E) alkyne

Question 35

Name the major alcohol product which results when 3,3-dimethylbut-1-ene is treated with dilute acid.

Question 36

Complete the following reaction and provide a detailed, step-by-step mechanism for the process.

Question 37

Draw the major organic product(s) generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 38

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 39

Which one of these alkene would be likely to experience a carbocation rearrangement when treated with aqueous acid?

A)
B)
C)
D) None of these would undergo a rearrangement.

Question 40

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 41

Which one of these alkene would be likely to experience a carbocation rearrangement when treated with Hg(OAc)₂ in water, followed by reaction with sodium borohydride?

A)
B)
C)
D) None of these would undergo a rearrangement.

Question 42

Provide the reagents necessary to complete the following transformation.

A) 1. BH₃^∙THF 2. H₂O₂, HO^-
B) H₂O, H₂SO₄
C) OsO₄, H₂O₂
D) CH₃CO₃H
E) 1. CH₃CO₃H 2. H⁺, H₂O

Question 43

Complete the following reaction by filling in the appropriate reagents.

Question 44

Provide the structure of the major organic product of the reaction below.

Question 45

Provide the structure of the major organic product of the reaction below.

Question 46

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 47

How many moles of BH₃ need to be added to completely react with 1 mole of hex-1-ene?

A) 1 mole of BH₃
B) 3 mole of BH₃
C) 1/3 mole of BH₃
D) 1/2 mole of BH₃

Question 48

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 49

When an alkene is subjected to treatment with Hg(OAc)₂ in alcohol followed by reaction with NaBH₄, what new class of compound is formed?

A) ether
B) epoxide
C) alkane
D) syn diol
E) alkyne

Question 50

Use a transition state to explain the regiochemistry of the reaction below. Make sure to include correct partial charges.

Question 51

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 52

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 53

Treatment of 2-methylpropene with which of the following reaction conditions results in an anti-Markovnikov addition product?

A) dry gaseous HBr with peroxides present
B) BH₃-THF, followed by alkaline H₂O₂
C) aqueous Hg(OAc)₂, followed by alkaline NaBH₄
D) dilute H₂SO₄ and heat
E) both A and B

Question 54

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 55

Provide the reagents necessary to convert 3-methyl-2-butanol to 2-methyl-2-butanol.

Question 56

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.
(Z)-3-hexene →

Question 57

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 58

Provide the structure of the major organic product of the reaction below.

Question 59

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 60

Provide the structure of the major organic product of the reaction below.

Question 61

Using any alkene as a starting material, how would you make the compound shown below?

Question 62

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 63

Consider how the I-Cl bond is polarized and predict the product which results when this mixed halogen adds to 1-methylcyclohexene.

Question 64

Draw a full and complete mechanism for the following reaction.

Question 65

Humulene is a monocyclic terpene constituent of carnations. When 0.25 mol of humulene is hydrogenated in the presence of platinum catalyst, 0.75 mol of H₂ reacts with the humulene to produce a monocyclic hydrocarbon of formula C₁₅H₃₀. What is the molecular formula of humulene?

Question 66

Which of the following alkenes will yield a meso dihalide when reacted with Br₂/CCl₄ at room temperature?

A)
B)
C)
D)
E) both Band D

Question 67

Provide the structure of the major organic product of the reaction below.

Question 68

Which of the following additions to alkenes occur(s) specifically in an anti fashion?

A) hydroboration-oxidation
B) addition of Br₂
C) addition of H₂
D) addition of H₂O in dilute acid
E) both A and B

Question 69

Predict the product of the following reaction. Include any relevant stereochemistry.

Question 70

Provide the major organic product of the reaction below.

Question 71

Both (E)- and (Z)-hex-3-ene can be treated with D₂ in the presence of a platinum catalyst. How are the products from these two reactions related to each other?

A) The (E)- and (Z)-isomers generate the same products but in differing amounts.
B) The (E)- and (Z)-isomers generate the same products in exactly the same amounts.
C) The products of the two isomers are related as constitutional isomers.
D) The products of the two isomers are related as diastereomers.
E) The products of the two isomers are related as enantiomers.

Question 72

Provide a detailed, step-by-step mechanism for the reaction shown below.

Question 73

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 74

Complete the following reaction and provide a detailed, step-by-step mechanism for the process.

Question 75

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 76

________ is the use of an optically active reagent or catalyst to convert an optically inactive starting material into an optically active product.

A) Asymmetric induction
B) Racemization
C) Optical reduction
D) Meso effection
E) Chiralization

Question 77

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 78

Addition of Br₂ to (E)-hex-3-ene produces ________.

A) a meso dibromide
B) a mixture of enantiomeric dibromides which is optically active
C) a mixture of enantiomeric dibromides which is optically inactive
D) (Z)-3,4-dibromo-3-hexene
E) (E)-3,4-dibromo-3-hexene

Question 79

Draw the major organic product generated in the reaction below. Pay particular attention to regio- and stereochemical detail.

Question 80

Draw the major organic product(s) generated in the reaction below. Pay particular attention to regio- and stereochemical detail.