Organic Chemistry

Paula Yurkanis Bruice

Chapter 6 The Reactions of Alkenes • The Stereochemistry of Addition Reactions - all with Video Answers

Educators

Chapter Questions

00:54

Problem 1

Draw the mechanism for the reaction of cyclohexene with HCI.

Dalton Hilovsky

Numerade Educator

01:17

Problem 2

a. How many $\sigma$ bond orbitals are available for overlap with the vacant $p$ orbital in the methyl cation?
b. Which is more stable: a methyl cation or an ethyl cation? Why?

Dalton Hilovsky

Numerade Educator

02:53

a. How many $\sigma$ bond orbitals are available for overlap with the vacant $p$ orbital in
1. the isobutyl cation?
2. the $n$ -butyl cation?
3. the sec-butyl cation?
b. Which of the carbocations in part a is most stable?

Dalton Hilovsky

Numerade Educator

01:24

Problem 4

Rank the following carbocations in each set from most stable to least stable:

Dalton Hilovsky

Numerade Educator

01:04

Problem 5

Is the structure of the transition state in the following reaction coordinate diagrams more similar to the structure of the reactant or to the structure of the product?

Dalton Hilovsky

Numerade Educator

01:23

Problem 6

To which compound is the addition of HBr more highly regioselective?

Dalton Hilovsky

Numerade Educator

02:32

Problem 7

What is the major product obtained from the addition of HBr to each of the following compounds?

Dalton Hilovsky

Numerade Educator

03:29

Problem 8

What alkene should be used to synthesize each of the following alkyl bromides?

Dalton Hilovsky

Numerade Educator

02:15

Problem 9

The $p K_{a}$ of a protonated alcohol is about $-2.5,$ and the $p K_{a}$ of an alcohol is about $15 .$ Therefore, as long as the pH of the solution is greater than ___ and less than ___, more than $50 \%$ of 2 -propanol (the product of the reaction on $\mathrm{p} .244$ ) will be in its neutral, nonprotonated form.

Dalton Hilovsky

Numerade Educator

00:46

Problem 10

Answer the following questions about the mechanism for the acid-catalyzed hydration of an alkene:
a. How many transition states are there?
b. How many intermediates are there?
c. Which step in the forward direction has the smallest rate constant?

Dalton Hilovsky

Numerade Educator

02:26

Problem 11

What is the major product obtained from the acid-catalyzed hydration of cach of the following alkencs?

Dalton Hilovsky

Numerade Educator

01:51

Problem 12

a. What is the major product of each of the following reactions?
b. What do all the reactions have in common?
c. How do all the reactions differ?

Dalton Hilovsky

Numerade Educator

01:11

Problem 13

How could the following compound be prepared using an alkene as one of the starting materials?
SOLUTION The desired compound- -called a target molecule-can be prepared by the acid-catalyzed addition of an alcohol to an alkene. There are three different combinations of an alkene and an alcohol that could be used for the synthesis of this particular ether. One requires a 3 -carbon alkene and a 4 -carbon alcohol; the other two require a 4-carbon alkene and a 3-carbon alcohol.

Dalton Hilovsky

Numerade Educator

03:59

Problem 14

How could the following compounds be prepared using an alkene as one of the starting materials?

Dalton Hilovsky

Numerade Educator

02:25

Problem 15

Propose a mechanism for the following reaction (remember to use curved arrows to show the movement of electrons from the nucleophile to the electrophile):

Dalton Hilovsky

Numerade Educator

01:27

Problem 16

Which of the following carbocations would you expect to rearrange?
SOLUTION
A is a secondary carbocation. It does not rearrange because a 1,2 -hydride shift would convert it to a different secondary carbocation, so there is no energetic advantage to the rearrangement.
B is a secondary carbocation. It rearranges because a 1,2 -hydride shift converts it to a more stable tertiary carbocation.
C is a tertiary carbocation. It does not rearrange because its stability is not improved by rearrangement.
D is a tertiary carbocation. It does not rearrange because its stability is not improved by rearrangement.
E is a secondary carbocation. It does rearrange because a 1,2 -hydride shift converts it to a more stable tertiary carbocation.
F is a secondary carbocation. It does not rearrange because rearrangement would form a carbocation with the same stability - that is, another secondary carbocation.

Dalton Hilovsky

Numerade Educator

03:22

Problem 17

What is the major product obtained from the reaction of HBr with each of the following?

Dalton Hilovsky

Numerade Educator

00:53

Problem 18

Which is more highly regioselective: reaction of an alkene with $\mathrm{BH}_{3}$ or with 9 -BBN?

Dalton Hilovsky

Numerade Educator

01:17

Problem 19

What is the major product obtained from hydroboration-oxidation of the following alkenes?
a. 2-methyl-2-butene $\quad$ b. 1 -methylcyclohexene

Dalton Hilovsky

Numerade Educator

01:25

Problem 20

What will be the product of the preceding reaction if HBr is used in place of $\mathrm{Br}_{2} ?$

Dalton Hilovsky

Numerade Educator

03:43

Problem 21

a. How does the first step in the reaction of propene with $\mathrm{Br}_{2}$ differ from the first step in the reaction of propene with HBr?
b. To understand why $\mathrm{Br}^{-}$ adds to a carbon of the bromonium ion rather than to the positively charged bromine, draw the product that would be obtained if $\mathrm{Br}^{-}$ did add to bromine.

Dalton Hilovsky

Numerade Educator

00:52

Problem 22

Why are $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ unable to form covalent bonds?

Dalton Hilovsky

Numerade Educator

03:12

Problem 23

Each of the following reactions has two nucleophiles that could add to the intermediate formed by the reaction of the alkene with an electrophile. What is the major product of each reaction?

Dalton Hilovsky

Numerade Educator

01:20

Problem 24

What is the product of the addition of $I-\mathrm{Cl}$ to $1-$ butene? (Hint: Chlorine is more electronegative than iodine [Table 1.3].)

Dalton Hilovsky

Numerade Educator

02:00

Problem 25

What will be the major product obtained from the reaction of $\mathrm{Br}_{2}$, with 1 -butene if the reaction is carried out in
a. dichloromethane?
b. water?
c. ethyl alcohol?
d. methyl alcohol?

Dalton Hilovsky

Numerade Educator

02:28

Problem 26

Propose a mechanism for the following reaction:

Dalton Hilovsky

Numerade Educator

01:58

Problem 27

Draw structures for the following:
a. 2 -propyloxirane
c. 2,2,3,3-tetramethyloxirane
b. cyclohexene oxide
d. 2,3 -epoxy-2-methylpentane

Dalton Hilovsky

Numerade Educator

02:39

Problem 28

What alkene would you treat with a peroxyacid in order to obtain each of the epoxides in Problem $27 ?$

Dalton Hilovsky

Numerade Educator

01:52

Problem 29

Identify each of the following reactions as an oxidation reaction, a reduction reaction, or neither.
SOLUTION TO 29 a. Recall that an oxidation reaction decreases the number of $\mathrm{C}-\mathrm{H}$ bonds and/or increases the number of $\mathrm{C}-\mathrm{O}, \mathrm{C}-\mathrm{N},$ or $\mathrm{C}-\mathrm{X}$ bonds (where $\mathrm{X}=\mathrm{a}$ halogen) (Section 6.8 ), whereas a reduction reaction increases the number of $\mathrm{C}-\mathrm{H}$ bonds and/or decreases the number of $\mathrm{C}-\mathrm{O}, \mathrm{C}-\mathrm{N}$ or $\mathrm{C}-\mathrm{X}$ bonds (Section 5.9 ). Therefore, this is an oxidation reaction because the number of $\mathrm{C}-\mathrm{Cl}$ bonds increases.
SOLUTION TO 29 b. The product has both a new C - O bond (signifying an oxidation) and a new C-H bond (signifying a reduction). Thus, the two cancel each other; the reaction is neither an oxidation nor a reduction.

Dalton Hilovsky

Numerade Educator

06:47

Problem 30

What products are formed when the following compounds react with ozone and then with dimethyl sulfide?

Dalton Hilovsky

Numerade Educator

01:47

Problem 31

a. What alkene would give only a ketone with three carbons as a product of oxidative cleavage?
b. What alkenes would give only an aldehyde with four carbons as a product of oxidative cleavage?

Dalton Hilovsky

Numerade Educator

00:45

Problem 32

What aspect of the structure of the alkene does ozonolysis not tell you?

Dalton Hilovsky

Numerade Educator

04:02

Problem 33

a. The following product was obtained from the ozonolysis of an alkene followed by treatment with dimethyl sulfide. What is the structure of the alkene?
b. The following products were obtained from the oxidative cleavage of a diene. What is the structure of the diene?
SOLUTION TO 33 a. Because only one product is obtained, the reactant must be a cyclic alkene. Numbering the product shows that the carbonyl groups are at $\mathrm{C}-1$ and $\mathrm{C}-6,$ so the double bond in the alkene must be between $\mathrm{C}-1$ and $\mathrm{C}-6,$.
SOLUTION TO 33 b. The five-carbon product with two carbonyl groups indicates that the diene must contain five carbons flanked by two double bonds.
One of the other two products obtained from ozonolysis has one carbon, and the other has three carbons. Therefore, one carbon must be added to one end of the diene, and three carbons must be added to the other end.

Dalton Hilovsky

Numerade Educator

02:35

Problem 34

The following product was obtained from the ozonolysis of an alkene followed by treatment with dimethyl sulfide. What is the structure of the alkene?

Dalton Hilovsky

Numerade Educator

01:08

Problem 35

What characteristics must the reactant of a stereospecific reaction have?

Dalton Hilovsky

Numerade Educator

02:28

Problem 36

a. Is the reaction of 2 -butene with HBr regioselective?
b. Is it stereoselective?
c. Is it stereospecific?
d. Is the reaction of 1-butene with HBr regioselective?
e. Is it stereoselective?
f. Is it stereospecific?

Dalton Hilovsky

Numerade Educator

03:56

Problem 37

What stereoisomers are obtained from each of the following reactions?

Dalton Hilovsky

Numerade Educator

01:51

Problem 38

Which product is obtained in greater yield from the preceding reaction?
Solution The methyl group attached to the $s p^{3}$ carbon in the reactant is sticking up, so it provides some steric hindrance to the approach of the chloride ion from above the planar carbocation. As a result, the product obtained in greater yield is the one formed by the approach of the chloride ion from below the plane.

Dalton Hilovsky

Numerade Educator

04:03

Problem 39

Using perspective formulas, draw the products obtained from the reaction of $(Z)-3,4$ -dimethyl- 3 -hexene with HCI.
Because the reaction forms a carbocation intermediate on the way to forming a product with two new asymmetric centers, four stereoisomers are formed. First draw the bonds about the asymmetric centers. (Remember that the lines in the plane must be adjacent and that the hatched wedge must be above the solid wedge.) Attach the groups to the bonds in any order, then draw the mirror image of the structure you just drew.
Next, draw a third structure by interchanging any two groups bonded to one of the asymmetric enters in one of the first two structures. Then draw the mirror image of the third structure.
Because the four stereoisomers formed by the cis alkene are identical to the four stereoisomers formed by the trans alkene, the reaction is also not stereospecific.

Lottie Adams

Numerade Educator

01:41

Problem 40

a. What stereoisomers are formed in the following reaction? Are they enantiomers or diastereomers?
b. Which stereoisomer is formed in greater yield?
SOLUTION 40 a. The reaction forms two stereoisomers because $\mathrm{H}_{2}$ can approach the plane of the double bond from above and below. The stereoisomers are diastereomers because the reactant has an asymmetric center and the product has a new second asymmetric center.
SOLUTION 40 b. Because the methyl group is pointing upward, it provides steric hindrance to $\mathrm{H}_{2}$ approaching the double bond from above. Therefore, the major product is $A$, the compound formed by $\mathrm{H}_{2}$ approaching the double bond from below.

Dalton Hilovsky

Numerade Educator

11:35

Problem 41

a. What alkene is required to synthesize each of the following compounds?
b. What other epoxide is formed in each synthesis?
c. Assign an $R$ or $S$ configuration to each asymmetric center.

Bhumika Jayee

Numerade Educator

08:53

Problem 42

What stereoisomers are obtained from hydroboration-oxidation of the following compounds? Assign an $R$ or $S$ configuration to each asymmetric center.
a. cyclohexene
b. 1-ethylcyclohexene
c. $c$ is- 2 -butene
d. $(Z)$-3,4 -dimethyl- 3 -hexene

Dalton Hilovsky

Numerade Educator

02:21

Problem 43

The reaction of 2 -ethyl-1-pentene with $\mathrm{Br}_{2}$, with $\mathrm{H}_{2}+\mathrm{Pd} / \mathrm{C}$, or with $\mathrm{R}_{2} \mathrm{BH} / \mathrm{THF}$ followed by aqueous $\mathrm{HO}^{-}+\mathrm{H}_{2} \mathrm{O}_{2}$ leads to a racemic mixture. Explain why a racemic mixture is obtained in each case.

Dalton Hilovsky

Numerade Educator

02:22

Problem 44

Using a sample of trans-2-pentene, how could you prove that the addition of $\mathrm{Br}_{2}$ forms a cyclic bromonium ion intermediate rather than a carbocation intermediate?
SOLUTION You could distinguish between the two intermediates by determining the number of products obtained from the reaction. If a cyclic intermediate is formed, then two products will be obtained, because only anti addition can occur. If a carbocation intermediate is formed, then four products will be obtained because both syn and anti addition can occur.

Dalton Hilovsky

Numerade Educator

03:12

Problem 45

What stereoisomers are obtained from the following reactions?
a. trans-2-butene $+\mathrm{HBr}$
b. $(Z)-3$ -methyl- 2 -pentene $+\mathrm{HBr}$
c. $(E)-3$ -methyl- 2 -pentene $+\mathrm{HBr}$
d. cis-3 -hexene $+\mathrm{HBr}$
e. cis- 2 -pentene $+\mathrm{Br}_{2}$
f. 1 -hexene $+\mathrm{Br}_{2}$

Lottie Adams

Numerade Educator

01:50

Problem 46

When $\mathrm{Br}_{2}$ adds to a cis alkene that has different substituents attached to each of the two $s p^{2}$ carbons, such as cis-2-heptene, identical amounts of the two threo enantiomers are obtained even though $\mathrm{Br}^{-}$ is more likely to add to the less sterically hindered carbon of the bromonium ion. Explain why identical amounts of the two enantiomers are obtained.

Lottie Adams

Numerade Educator

01:19

Problem 47

a. What products will be obtained from the addition of $\mathrm{Br}_{2}$ to cyclohexene if $\mathrm{H}_{2} \mathrm{O}$ is added to the reaction mixture?
b. Propose a mechanism for the reaction.

Lottie Adams

Numerade Educator

01:33

Problem 48

What stereoisomers would you expect to obtain from each of the following reactions?

Lottie Adams

Numerade Educator

01:58

Problem 49

What stereoisomers would you expect to obtain from each of the following reactions?

Lottie Adams

Numerade Educator

01:05

Problem 50

a. What is the major product obtained from the reaction of propene and $\mathrm{Br}_{2}$ plus excess $\mathrm{Cl}^{-}$ ?
b. Indicate the relative amounts of the stereoisomers that are obtained.

Lottie Adams

Numerade Educator

01:36

Problem 51

a. What is the product of the reaction of fumarate and $\mathrm{H}_{2} \mathrm{O}$ when $\mathrm{H}_{2} \mathrm{SO}_{4}$ is used as a catalyst instead of fumarase?
b. What is the product of the reaction of maleate and $\mathrm{H}_{2} \mathrm{O}$ when $\mathrm{H}_{2} \mathrm{SO}_{4}$ is used as a catalyst instead of fumarase?

Lottie Adams

Numerade Educator

03:48

Problem 52

Show how each of the following compounds can be synthesized from an alkene:
SOLUTION TO 52 a. The only alkene that can be used for this synthesis is cyclohexene. To get the desired substituents on the ring, cyclohexene must react with $\mathrm{Cl}_{2}$ in an aqueous solution so that water will be the nucleophile.
SOLUTION TO 52 b. The alkene that should be used here is 1-methylcyclohexene. To get the substituents in the desired locations, the electrophile must be $\mathrm{R}_{2} \mathrm{BH}$ or $\mathrm{BH}_{3}$, with HO taking boron's place in the subsequent oxidation reaction.

Anish Wadhwa

Numerade Educator

07:01

Problem 53

Show how each of the following compounds can be synthesized from an alkene:

Anish Wadhwa

Numerade Educator

01:04

Problem 54

Explain why 3 -methylcyclohexene should not be used as the starting material in Problem $52 \mathrm{b}$.

Lottie Adams

Numerade Educator

04:18

Problem 55

What is the major product of each of the following reactions?

Anish Wadhwa

Numerade Educator

02:01

Problem 56

Which electrophilic addition reactions
a. form a carbocation intermediate?
b. form no intermediate?
c. form a three-membered ring intermediate?
d. form a five-membered ring intermediate?

Lottie Adams

Numerade Educator

01:20

Problem 57

Identify the electrophile and the nucleophile in each of the following reaction steps and then draw curved arrows to illustrate the bond-making and bond-breaking processes.

Lottie Adams

Numerade Educator

07:32

Problem 58

What is the major product of the reaction of 2 -methyl- 2 -butene with each of the following reagents?
a. $\mathrm{HBr}$
b. $\mathrm{HI}$
c. $\mathrm{Cl}_{2} / \mathrm{CH}_{2} \mathrm{Cl}_{2}$
d. $\mathrm{O}_{3},-78^{\circ} \mathrm{C},$ followed by $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{S}$
e. $\mathrm{H}_{2} / \mathrm{Pd}$
f. MCPBA (a peroxyacid)
g. $\mathrm{H}_{2} \mathrm{O}+\mathrm{H}_{2} \mathrm{SO}_{4}$
h. $\mathrm{Br}_{2} / \mathrm{CH}_{2} \mathrm{Cl}_{2}$
i. $ \mathrm{Br}_{2} / \mathrm{H}_{2} \mathrm{O}$
j. $ \mathrm{Br}_{2} / \mathrm{CH}_{3} \mathrm{OH}$
k. $\mathrm{BH}_{3} / \mathrm{THF}$, followed by $\mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{HO}^{-}, \mathrm{H}_{2} \mathrm{O}$

Anish Wadhwa

Numerade Educator

01:32

Problem 59

Give two names for each of the following:

Lottie Adams

Numerade Educator

02:07

Problem 60

What reagents are needed to synthesize the following alcohols?

Anish Wadhwa

Numerade Educator

00:49

Problem 61

What are the products of the following reactions? Indicate whether each reaction is an oxidation or a reduction.

Lottie Adams

Numerade Educator

01:10

Problem 62

When 3-methyl-1-butene reacts with HBr, two alkyl halides are formed: 2-bromo-3-methylbutane and 2-bromo-2-methylbutane. Propose a mechanism that explains the formation of these two products.

Lottie Adams

Numerade Educator

01:28

Problem 63

Draw curved arrows to show the flow of electrons responsible for the conversion of the following reactants into products:

Lottie Adams

Numerade Educator

03:19

Problem 64

What reagents are needed to carry out the following syntheses?

Anish Wadhwa

Numerade Educator

01:00

Problem 65

a. Identify two alkenes that react with HBr to form 1-mcthylcyclohexane without undergoing a carbocation rearrangement.
b. Would both alkenes form the same alkyl halide if DBr were used instead of HBr? (D is an isotope of $\mathrm{H},$ so $\mathrm{D}^{+}$ reacts like $\mathrm{H}^{+}$.)

Lottie Adams

Numerade Educator

03:30

Problem 66

What is the major product of each of the following reactions?

Anish Wadhwa

Numerade Educator

04:34

Problem 67

Using any alkene and any other reagents, how would you prepare the following compounds?

Anish Wadhwa

Numerade Educator

01:47

Problem 68

Which is more stable?

Lottie Adams

Numerade Educator

01:08

Problem 69

a. Use curved arrows to show the flow of electrons that occurs in each step of the following mechanism.
b. Draw a reaction coordinate diagram for the reaction. (Hint: An alkyl halide is more stable than an alkene.)

Lottie Adams

Numerade Educator

07:34

Problem 70

a. Draw the product or products that will be obtained from the reaction of cis -2-butene and trans-2-butene with each of the following reagents. If a product can exist as stereoisomers, show which stereoisomers are formed.
1. $\mathrm{HCI}$
2. $\mathrm{BH}_{3} / \mathrm{THF}$, followed by $\mathrm{HO}^{-}, \mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{H}_{2} \mathrm{O}$
3. a peroxyacid
4. $\mathrm{Br}_{2}$ in $\mathrm{CH}_{2} \mathrm{Cl}_{2}$
5. $\mathrm{Br}_{2}+\mathrm{H}_{2} \mathrm{O}$
6. $\mathrm{H}_{2}+\mathrm{Pd} / \mathrm{C}$
7. $\mathrm{H}_{2} \mathrm{O}+\mathrm{H}_{2} \mathrm{SO}_{4}$
8. $\mathrm{CH}_{3} \mathrm{OH}+\mathrm{H}_{2} \mathrm{SO}_{4}$

Lottie Adams

Numerade Educator

01:46

Problem 71

1-Methylcyclohexene forms two products when it reacts with bromine in methanol.
a. Draw the mechanism for the formation of the products.
b. Describe their stereochemical relationship - that is, are they enantiomers or diastereomers?

Lottie Adams

Numerade Educator

02:44

Problem 72

The second-order rate constant (in units of $\mathbf{M}^{-1} \mathbf{s}^{-1}$ ) for acid-catalyzed hydration at $25^{\circ} \mathrm{C}$ is given for each of the following alkenes:
a. Calculate the relative rates of hydration of the alkenes. (Hint: Divide each rate constant by the smallest rate constant of the series: $3.51 \times 10^{-8}$.)
b. Why does (Z)-2-butene react faster than ( $E$ )-2-butene?
c. Why does 2 -methyl- 2 -butene react faster than $(Z)$ - 2 -butene?
d. Why does 2,3 -dimethyl- 2 -butene react faster than 2 -methyl- 2 -butene?

Lottie Adams

Numerade Educator

01:27

Problem 73

Which compound has the greater dipole moment?

Lottie Adams

Numerade Educator

03:05

Problem 74

Draw the products of the following reactions. If the products can exist as stereoisomers, show which stereoisomers are formed.

Lottie Adams

Numerade Educator

01:33

Problem 75

A student was about to turn in the products he had obtained from the reaction of HI with 3,3,3 -trifluoropropene when he realized that the labels had fallen off his flasks and he did not know which label belonged to which flask. His friend reminded him of the rule that says the electrophile adds to the $s p^{2}$ carbon bonded to the most hydrogens. In other words, he should label the flask containing the most product 1,1,1 -trifluoro- 2 -iodopropane and label the flask containing the least amount of product 1,1,1 -trifluoro- 3 -iodopropane. Should he follow his friend's advice?

Lottie Adams

Numerade Educator

02:40

Problem 76

a. Propose a mechanism for the following reaction (show all curved arrows):
b. Which step is the rate-determining step?
c. What is the electrophile in the first step?
d. What is the nucleophile in the first step?
e. What is the electrophile in the second step?
f. What is the nucleophile in the second step?

Lottie Adams

Numerade Educator

02:54

Problem 77

Draw the products, including their configurations, obtained from the reaction of 1-ethylcyclohexene with the following reagents:
a. $\mathrm{HBr}$
b. $\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$
c. $\mathrm{R}_{2} \mathrm{BH} / \mathrm{THF},$ followed by $\mathrm{HO}^{-}, \mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{H}_{2} \mathrm{O}$
d. $\mathrm{Br}_{2} / \mathrm{CH}_{2} \mathrm{Cl}_{2}$

Anish Wadhwa

Numerade Educator

01:12

Problem 78

Which stereoisomer of 3-hexene forms a meso compound when it reacts with $\mathrm{Br}_{2} ?$

Lottie Adams

Numerade Educator

02:59

Problem 79

Which stereoisomer of 3-hexene forms (35,4S)-4-bromo-3-hexanol and (3R,4R)-4-bromo-3-hexanol when it reacts with $\mathrm{Br}_{2}$ and $\mathrm{H}_{2} \mathrm{O} ?$

Anish Wadhwa

Numerade Educator

01:58

Problem 80

Propose a mechanism for each of the following reactions:

Lottie Adams

Numerade Educator

01:12

Problem 81

What is the major product of each of the following reactions?
$$\text { a. } \mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2}+\mathrm{Br}_{2} \quad \overrightarrow{\mathrm{CH}_{2} \mathrm{Cl}_{2}}$$
$$\text { b. } \mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2}+\mathrm{Br}_{2} \quad \overrightarrow{\mathrm{CH}_{2} \mathrm{Cl}_{2}}$$

Lottie Adams

Numerade Educator

05:16

Problem 82

Draw the products of the following reactions. If the products isomers, show which stereoisomers are formed.
a. $cis- 2$ -pentene $+\mathrm{HCl}$
b. trans-2-pentene + HCl
c. 1 -ethylcyclohexene $+\mathrm{H}_{2} \mathrm{O}+\mathrm{H}_{2} \mathrm{SO}_{4}$
d. 2,3 -dimethyl- 3 -hexene $+\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$
e. 1,2 -dimethylcyclohexene $+\mathrm{HCl}$
f. 1,2 -dideuteriocyclohexene $+\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$
g. 3,3 -dimethyl- 1 -pentene $+\mathrm{Br}_{2} / \mathrm{CH}_{2} \mathrm{Cl}_{2}$
h. $(E)-3,4$ -dimethyl- 3 -heptene $+\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$
i. $(Z)-3.4$ -dimethyl- 3 -heptene $+\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$
j. $1$ -chloro- 2 -ethylcyclohexene $+\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$

Lottie Adams

Numerade Educator

01:56

Problem 83

a. What product is obtained from the reaction of $\mathrm{HCl}$ with 1-butene? With 2-butene?
b. Which of the two reactions has the greater free energy of activation?
c. Which compound reacts more rapidly with HCl: (Z)-2-butene or (E)-2-butene?

Lottie Adams

Numerade Educator

01:44

Problem 84

What is the major product of the reaction of each of the following with HBr?

Lottie Adams

Numerade Educator

01:50

Problem 85

For each compound, show the products obtained from ozonolysis, followed by treatment with dimethyl sulfide.

Lottie Adams

Numerade Educator

01:30

Problem 86

Which stereoisomer of 3,4 -dimethyl- 3 -hexene forms $(3 S, 4 S)-3,4$ -dimethylhexane and $-(3 R, 4 R)-3,4$ -dimethylhexane when it reacts with $\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C} ?$

Lottie Adams

Numerade Educator

05:27

Problem 87

Draw the products of the following reactions. If the products can exist as stereoisomers show what stereoisomers are formed.
a. $cis- 2$ -pentene $+\mathrm{Br}_{2} / \mathrm{CH}_{2} \mathrm{Cl}_{2}$
b. trans-2-pentene $+\mathrm{Br}_{2} / \mathrm{CH}_{2} \mathrm{Cl}_{2}$
c. 1 -butene $+\mathrm{HCl}$
e. trans-3-hexene $+\mathrm{Br}_{2} / \mathrm{CH}_{2} \mathrm{Cl}_{2}$
f. $cis-3$-hexene $+\mathrm{Br}_{2} / \mathrm{CH}_{2} \mathrm{Cl}_{2}$
g. 3,3 -dimethyl- 1 -pentene $+\mathrm{HBr}$
h. $cis-2$-butene $+\mathrm{HBr}$
i. $(Z)-2,3$ -dichloro- 2 -butene $+\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$
j. $(E)-2,3$ -dichloro- 2 -butene $+\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$
k. $(Z)-3,4$ -dimethyl- 3 -hexene $+\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$
L. $(E)-3,4$ -dimethyl- 3 -hexene $+\mathrm{H}_{2}, \mathrm{Pd} / \mathrm{C}$

Lottie Adams

Numerade Educator

00:58

Problem 88

Of the possible products shown for the following reaction, are there any that will not be formed?

Lottie Adams

Numerade Educator

01:09

Problem 89

A, a compound with molecular formula $\mathrm{C}_{6} \mathrm{H}_{10},$ contains three methylene units. A reacts with one equivalent of $\mathrm{H}_{2}$ over $\mathrm{Pd} / \mathrm{C}$ to yield $\mathbf{B}$. A reacts with aqueous acid to form a single product, $\mathbf{C},$ and undergoes hydroboration/oxidation to form a pair of enantiomers, $\mathbf{D}$ and $\mathbf{E}$. Ozonolysis of $\mathbf{A}$ followed by reaction with dimethyl sulfide forms $\mathbf{F}$ with molecular formula $\mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}_{2} .$ Provide structures for $\mathbf{A}-\mathbf{F}$.

Lottie Adams

Numerade Educator

01:10

Problem 90

The reaction of an alkene with diazomethane forms a cyclopropane ring. Propose a mechanism for the reaction. (Hint: It is a concerted reaction.)
Note: Diazomethane is a gas that must be handled with great care because it is both explosive and toxic.

Lottie Adams

Numerade Educator

01:32

Problem 91

Two chemists at Dupont found that $\mathrm{ICH}_{2} \mathrm{ZnI}$ is better than diazomethane at converting a $\mathrm{C}=\mathrm{C}$ bond to a cylcopropane ring. Propose a mechanism for the reaction, now known as the Simmons-Smith reaction in their honor.

Lottie Adams

Numerade Educator

01:16

Problem 92

a. Dichlorocarbene can be generated by heating chloroform with $\mathrm{HO}^{-}$. Propose a mechanism for the reaction.
b. Dichlorocarbene can also be generated by heating sodium trichloroacetate. Propose a mechanism for the reaction.

Lottie Adams

Numerade Educator

00:40

Problem 93

What product is obtained from the reaction of dichlorocarbene with cyclopentene?

Lottie Adams

Numerade Educator

01:10

Problem 94

What alkene gives the product shown after reaction first with ozone and then with dimethyl sulfide?

Lottie Adams

Numerade Educator

03:45

Problem 95

Draw the products of the following reactions, including their configurations:

Lottie Adams

Numerade Educator

01:43

Problem 96

a. Propose a mechanism for the following reaction:
b. Is the initially formed carbocation primary, secondary, or tertiary?
c. Is the rearranged carbocation primary, secondary, or tertiary?
d. Why does the rearrangement occur?

Lottie Adams

Numerade Educator

00:57

Problem 97

Which compound is hydrated more rapidly?

Lottie Adams

Numerade Educator

01:23

Problem 98

When the following compound is hydrated in the presence of acid, the unreacted alkene is found to have retained the deuterium atoms. What does this tell you about the mechanism for hydration?

Lottie Adams

Numerade Educator

00:43

Problem 99

When fumarate reacts with $\mathrm{D}_{2} \mathrm{O}$ in the presence of the enzyme fumarase, only one isomer of the product is formed, as shown here. Is the enzyme catalyzing a syn or an anti addition of $\mathrm{D}_{2} \mathrm{O} ?$

Lottie Adams

Numerade Educator

00:52