Organic Chemistry

Janice Gorzynski Smith

Chapter 10

Alkenes and Addition Reactions - all with Video Answers

Educators

Chapter Questions

Problem 1

Calculate the number of degrees of unsaturation in a compound of molecular formula $\mathrm{C}_{4} \mathrm{H}_{6}$, and propose possible structures.

Timothy Gailey

Timothy Gailey

Numerade Educator

Problem 2

Calculate the number of degrees of unsaturation for each molecular formula, and propose two possible structures:
(a) $\mathrm{C}_{8} \mathrm{H}_{12} ;$ (b) $\mathrm{C}_{10} \mathrm{H}_{10}$

Timothy Gailey

Numerade Educator

Problem 3

How many degrees of unsaturation are present in each compound?
a. $\mathrm{C}_{6} \mathrm{H}_{6}$
b. $\mathrm{C}_{8} \mathrm{H}_{18}$
c. $\mathrm{C}_{7} \mathrm{H}_{8} \mathrm{O}$
d. $\mathrm{C}_{7} \mathrm{H}_{11} \mathrm{Br}$
e. $\mathrm{C}_{5} \mathrm{HgN}$

Timothy Gailey

Numerade Educator

Problem 4

How many degrees of unsaturation does each of the following drugs contain?
a. zolpidem (sleep aid sold as Ambien), $\mathrm{C}_{19} \mathrm{H}_{21} \mathrm{~N}_{3} \mathrm{O}$
b. mefloquine (antimalarial drug), $\mathrm{C}_{17} \mathrm{H}_{16} \mathrm{~F}_{6} \mathrm{~N}_{2} \mathrm{O}$

Timothy Gailey

Numerade Educator

Problem 5

Give the IUPAC name for each alkene.
a.
b.
c.
d.
d.
e.

Timothy Gailey

Numerade Educator

Problem 6

Give the IUPAC name for each polyfunctional compound.
a.
b.
c.

Timothy Gailey

Numerade Educator

Problem 7

Label each C-C double bond as $E$ or $z$.
a.
b.
c.
d.

Timothy Gailey

Numerade Educator

Problem 8

A is a toxin produced by the poisonous seaweed Chlorodesmis fastigiata. (a) Label each alkene that exhibits stereoisomerism as $E$ or $Z$. (b) Draw a stereoisomer of A that has all $Z$
double bonds.

Timothy Gailey

Numerade Educator

Problem 9

Draw the structure corresponding to each IUPAC name.
a. ( $Z$ )-4-ethylhept-3-ene
b. $(E)-3,5,6$ -trimethyloct- 2 -ene
c. (Z)-2-bromo-1-iodohex-1-ene

Timothy Gailey

Numerade Educator

Problem 10

Rank the following isomers in order of increasing boiling point.

Lashan De Silva

Lashan De Silva

University of Houston

Problem 11

Linolenic acid (Table 10.2 ) and stearidonic acid are omega-3 fatty acids, unsaturated fatty acids that contain the first double bond located at $\mathrm{C} 3$, when numbering begins at the methyl end of the chain. Predict how the melting point of stearidonic acid compares with the melting points of linolenic and stearic acids. A current avenue of research is
examining the use of soybean oil enriched in stearidonic acid as a healthier alternative to
vegetable oils that contain fewer degrees of unsaturation.

Ian Kaigh

Numerade Educator

Problem 12

Draw the products of each elimination reaction.
a.
b.

Timothy Gailey

Numerade Educator

Problem 13

What product is formed when each alkene is treated with HCI?
a.
b.
c.

Timothy Gailey

Numerade Educator

Problem 14

Draw a stepwise mechanism for the following reaction. Draw the transition state for each
step.

Lashan De Silva

Lashan De Silva

University of Houston

Problem 15

Draw the products formed when each alkene is treated with HCI.
a.
b.
c.

Timothy Gailey

Numerade Educator

Problem 16

Use the Hammond postulate to explain why $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{C}=\mathrm{CH}_{2}$ reacts faster than $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2}$ in electrophilic addition of $\mathrm{HX}$.

Lashan De Silva

Lashan De Silva

University of Houston

Problem 17

Treatment of 3 -methylcyclohexene with HCl yields two products, 1-chloro-3methylcyclohexane and 1-chloro-1-methylcyclohexane. Draw a mechanism to explain
this result.

Timothy Gailey

Numerade Educator

Problem 18

Addition of HBr to which of the following alkenes will lead to a rearrangement?
a.
b.
c.

Timothy Gailey

Numerade Educator

Problem 19

Draw the products, including stereochemistry, of each reaction.
a.
b.

Timothy Gailey

Numerade Educator

Problem 20

Draw all stereoisomers formed when 1,2 -dimethylcyclohexene is treated with $\mathrm{HCl}$. Label
pairs of enantiomers.

Timothy Gailey

Numerade Educator

Problem 21

What two alkenes give rise to each alcohol as the major product of acid-catalyzed hydration?
a.
b.
c.

Timothy Gailey

Numerade Educator

Problem 22

What stereoisomers are formed when pent-1-ene is treated with $\mathrm{H}_{2} \mathrm{O}$ and $\mathrm{H}_{2} \mathrm{SO}_{4}$ ?

Timothy Gailey

Numerade Educator

Problem 23

Draw the products of each reaction, including stereochemistry.
a.
b.

Timothy Gailey

Numerade Educator

Problem 24

Draw all stereoisomers formed in each reaction.
a.
b.
c.

Timothy Gailey

Numerade Educator

Problem 25

Draw the products of each reaction and indicate their stereochemistry.
a.
b.

Timothy Gailey

Numerade Educator

Problem 26

What alkylborane is formed from hydroboration of each alkene?
a.
b.
c.

Nicole Krahulik

Nicole Krahulik

Numerade Educator

Problem 27

Draw the products formed when each alkene is treated with $\mathrm{BH}_{3}$ followed by $\mathrm{H}_{2} \mathrm{O}_{2}$, HO $^{-}$. Include the stereochemistry at all stereogenic centers.
a.
b.
c.

Nicole Krahulik

Nicole Krahulik

Numerade Educator

Problem 28

What alkene can be used to prepare each alcohol as the exclusive product of a two-step hydroboration-oxidation sequence?
a.
b.
c.

Nicole Krahulik

Nicole Krahulik

Numerade Educator

Problem 29

Draw the constitutional isomer formed when the following alkenes are treated with
each set of reagents: $[1] \mathrm{H}_{2} \mathrm{O}, \mathrm{H}_{2} \mathrm{SO}_{4} ;$ or [2] $\mathrm{BH}_{3}$ followed by $\mathrm{H}_{2} \mathrm{O}_{2},-\mathrm{OH} .$
a.
b.
c.

Kaden Bunch

Numerade Educator

Problem 30

Draw the products of each reaction using the two-part strategy from Sample Problem 10.7 .
a.
b.
c.

Kaden Bunch

Numerade Educator

Problem 31

Devise a synthesis of each compound from the indicated starting material.
a.
b.

Kaden Bunch

Numerade Educator

Problem 32

Give the IUPAC name for each compound.
a.
b.

Nicole Krahulik

Nicole Krahulik

Numerade Educator

Problem 33

(a) Label the carbon-carbon double bond in A as $E$ or $Z$. (b) Draw the products (including stereoisomers) formed when $\mathrm{A}$ is treated with $\mathrm{H}_{2} \mathrm{O}$ in the presence of $\mathrm{H}_{2} \mathrm{SO}_{4}$.

Ian Kaigh

Numerade Educator

Problem 34

Name the alkene depicted in the ball-and-stick model, and draw the constitutional isomers formed when the alkene is treated with each reagent:
(a) $\mathrm{Br}_{2} ;$ (b) $\mathrm{Br}_{2}$ in $\mathrm{H}_{2} \mathrm{O} ;$ (c) $\mathrm{Br}_{2}$ in $\mathrm{CH}_{3} \mathrm{OH}$.

Lashan De Silva

Lashan De Silva

University of Houston

Problem 35

Calculate the number of degrees of unsaturation for each molecular formula.
a. $\mathrm{C}_{6} \mathrm{H}_{8}$
b. $\mathrm{C}_{40} \mathrm{H}_{56}$
c. $\mathrm{C}_{10} \mathrm{H}_{16} \mathrm{O}_{2}$
d. $\mathrm{C}_{8} \mathrm{H}_{9} \mathrm{Br}$
e. $\mathrm{C}_{8} \mathrm{H}_{9} \mathrm{ClO}$
f. $\mathrm{C}_{7} \mathrm{H}_{11} \mathrm{~N}$
$\mathrm{g} \cdot \mathrm{C}_{4} \mathrm{H}_{8} \mathrm{BrN}$
h. $\mathrm{C}_{10} \mathrm{H}_{18}$ CINO

Kaden Bunch

Numerade Educator

Problem 36

How many rings and $\pi$ bonds does a compound with molecular formula $\mathrm{C}_{10} \mathrm{H}_{14}$ possess? List all possibilities.

Lashan De Silva

Lashan De Silva

University of Houston

Problem 37

Label the alkene in each drug as $E$ or $Z$. Enclomiphene is one component of the fertility drug Clomid. Tamoxifen is an anticancer drug. Clavulanic acid is sold in combination with the antibiotic amoxicillin under the trade name Augmentin.
a.
b.
c.

Nicole Krahulik

Nicole Krahulik

Numerade Educator

Problem 38

Give the IUPAC name for each compound.
a.
b.
c.
d.
e.
f.

Kaden Bunch

Numerade Educator

Problem 39

Give the structure corresponding to each name.
a. (E)-4-ethylhept-3-ene
b. 3,3-dimethylcyclopentene
c. 4-vinylcyclopentene
d. $(Z)-3$ -isopropylhept-2-ene
e. $c l s-3,4$ -dimethylcyclopentene
f. 1-isopropyl-4-propylcyclohexene
g. 3,4-dimethylcyclohex-2-enol
h. 3,5-diethylhex-5-en-3-ol

Kaden Bunch

Numerade Educator

Problem 40

(a) Draw all possible stereoisomers of 4-methylnon-2-ene, and name each isomer, including its $E, Z$ and $R, S$ prefixes. (b) Label two pairs of enantiomers. (c) Label four pairs of diastereomers.

Kaden Bunch

Numerade Educator

Problem 41

(a) Draw the structure of $(1 E, 4 R)-1,4$ -dimethylcyclodecene. (b) Draw the enantiomer and name it, including its $E, Z$ and $R, S$ prefixes.
(c) Draw two diastereomers and name them, including the $E, Z$ and $R, S$ prefixes.

Ian Kaigh

Numerade Educator

Problem 42

(a) Name the following compound including $E, Z$ and $R, S$ designations. (b) Draw a stereoisomer at the carbon-carbon double bond. (c) Draw a stereoisomer at the stereogenic center.

Kaden Bunch

Numerade Educator

Problem 43

Now that you have learned how to name alkenes in Section 10.3 , name each of the following epoxides as an alkene oxide, as described in Section 9.3 .
a.
b.
c.
d.

Kaden Bunch

Numerade Educator

Problem 44

lejimalide $\mathrm{B}$, an anticancer agent with a 24 -membered ring, is isolated from a tunicate found off le Island in Okinawa. (a) Label each double bond in iejimalide $\mathrm{B}$ as $E$ or $Z .$ (b) Label each tetrahedral stereogenic center as $R$ or $S .$ (c) How many stereoisomers are possible for iejimalide B?

Lashan De Silva

Lashan De Silva

University of Houston

Problem 45

Eleostearic acid is an unsaturated fatty acid obtained from the seeds of the tung oil tree (Aleurites fordii), a deciduous tree native to China. (a) Draw the structure of a stereoisomer that has a higher melting point than eleostearic acid. (b) Draw the structure of a stereoisomer that has a Iower melting point.

Kaden Bunch

Numerade Educator

Problem 46

Draw the products formed when $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{C}=\mathrm{CH}_{2}$ is treated with each reagent.
a. HBr
$\mathrm{b} \cdot \mathrm{H} 2 \mathrm{O}, \mathrm{H}_{2} \mathrm{SO}_{4}$
c. $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}, \mathrm{H}_{2} \mathrm{SO}_{4}$
d. $\mathrm{Cl}_{2}$
e. $\mathrm{Br}_{2}, \mathrm{H}_{2} \mathrm{O}$
f. NBS (aqueous DMSO)
g.[1] $\mathrm{BH}_{3} ;[2] \mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{HO}^{-}$

Kaden Bunch

Numerade Educator

Problem 47

What alkene can be used to prepare each alkyl halide or dihalide as the exclusive or major product of an addition reaction?
a.
b.
c.
d.

Kaden Bunch

Numerade Educator

Problem 48

Which alcohols can be prepared as a single product by hydroborationoxidation of an alkene? Which alcohols can be prepared as a single product by the acid-catalyzed addition of $\mathrm{H}_{2} \mathrm{O}$ to an alkene?
a.
b.
c.
d.

Kaden Bunch

Numerade Educator

Problem 49

Draw the constitutional isomer formed in each reaction.
a.
b.
c.
d.

Adedamola Opalade

Adedamola Opalade

Numerade Educator

Problem 50

What three alkenes (excluding stereoisomers) can be used to prepare 3chloro-3-methylhexane by addition of HCl?

Vipin Singh

Numerade Educator

Problem 51

What three alkenes (excluding stereoisomers) can be used to prepare 3 chloro-3-methylhexane by addition of HCl?
a.
b.
c.
d.

Nicole Krahulik

Nicole Krahulik

Numerade Educator

Problem 52

Draw the products of each reaction, including stereoisomers.
a.
b.
c.
d.
e.
f.
g.
h.

Ian Kaigh

Numerade Educator

Problem 53

Which alkene reacts faster with HBr? Explain your choice.
a
b

Zubair Abdulla

Numerade Educator

Problem 54

(a) What alkene yields $A$ and $B$ when it is treated with $B r_{2}$ in $C C l_{4} ?$ (b) What alkene yields $C$ and $D$ under the same conditions?
A
B
C
D

Biplab Das

Numerade Educator

Problem 55

Draw a stepwise mechanism for the following reaction.

Colton K

Numerade Educator

Problem 56

Draw a stepwise mechanism for the following reaction, which results in ring expansion of a six-membered ring to a seven-membered ring.

Tom Rutherford

Numerade Educator

Problem 57

Draw a stepwise mechanism for the conversion of hex-5-en-1-ol to the cyclic ether $\mathrm{A}$.

Nima Gharibi

Numerade Educator

Problem 58

Draw a stepwise mechanism that shows how all three alcohols are formed from the bicyclic alkene.

Aadit Sharma

Numerade Educator

Problem 59

Less stable alkenes can be isomerized to more stable alkenes by treatment with strong acid. For example, 2,3 -dimethylbut-1-ene is converted to 2,3 -dimethylbut-2-ene when treated with $\mathrm{H}_{2} \mathrm{SO}_{4}$. Draw a stepwise mechanism for this isomerization process.

Vipin Singh

Numerade Educator

Problem 60

When buta-1,3-diene (CH $_{2}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2}$ ) is treated with HBr, two constitutional isomers are formed, $\mathrm{CH}_{3} \mathrm{CHBrCH}=\mathrm{CH}_{2}$ and $\mathrm{BrCH}_{2} \mathrm{CH}=\mathrm{CHCH}_{3}$. Draw a stepwise mechanism that accounts for the formation of both products.

Vipin Singh

Numerade Educator

Problem 61

Explain why the addition of HBr to alkenes $A$ and $C$ is regioselective, forming addition products $\mathrm{B}$ and $\mathrm{D},$ respectively.
A
B
C
D

Ian Kaigh

Numerade Educator

Problem 62

Bromoetherification, the addition of the elements of Br and OR to a double bond, is a common method for constructing rings containing oxygen atoms. This reaction has been used in the synthesis of the polyether antibiotic monensin (Problem 18.34 ). Draw a stepwise mechanism for the following intramolecular bromoetherification reaction.

Ian Kaigh

Numerade Educator

Problem 63

Devise a synthesis of each product from the given starting material. More than one step is required.
a.
b.
c.
d.
e.
f.

Ian Kaigh

Numerade Educator

Problem 64

Devise a synthesis of each compound from cyclohexene as the starting material. More than one step is needed.
a.
b.
c.

Ian Kaigh

Numerade Educator

Problem 65

When 2 -bromo-3,3-dimethylbutane is treated with $\mathrm{K}^{+-} \mathrm{OC}\left(\mathrm{CH}_{3}\right)_{3},$ a single product $T$ having molecular formula $\mathrm{C}_{6} \mathrm{H}_{12}$ is formed. When 3,3 dimethylbutan-2-ol is treated with $\mathrm{H}_{2} \mathrm{SO}_{4}$, the major product $\mathrm{U}$ has the same molecular formula. Given the following ${ }^{1} \mathrm{H}$ NMR data, what are the structures of $T$ and $U$ ? Explain in detail the splitting patterns observed for the three split signals in T.
${ }^{1} \mathrm{H}$ NMR of T: 1.01 (singlet, $9 \mathrm{H}$ ), 4.82 (doublet of doublets, $1 \mathrm{H}, \mathrm{J}=10,1.7$
Hz), 4.93 (doublet of doublets, 1 H, $J=18,1.7$ Hz), and 5.83 (doublet of
doublets, $1 \mathrm{H}, \mathrm{J}=18,10 \mathrm{~Hz}$ ) ppm $^1$ H NMR of U: 1.60 (singlet) ppm
Additional problems on the spectroscopy of alkenes are given in Chapters A-C:
$\bullet$Mass spectrometry: $\mathrm{A.16b}, \mathrm{A.} 20, \mathrm{A.} 23$
$\bullet$Infrared spectroscopy: $\mathrm{B.5}, \mathrm{B} .7(\mathrm{~A}), \mathrm{B} .12 \mathrm{c}, \mathrm{B} 17 \mathrm{a}, \mathrm{B} .18 \mathrm{c}$
Nuclear magnetic resonance spectroscopy: C.12a; C.15d, e; C.29d; C.32d;
$\bullet$C.37; $\mathrm{C.38d}, \mathrm{f} ; \mathrm{C} .43 \mathrm{i}, \mathrm{j} ; \mathrm{C} .44 ; \mathrm{C} .45 ; \mathrm{C} .49 \mathrm{~d}, \mathrm{f} ; \mathrm{C} .50 \mathrm{~b} ; \mathrm{C} .51 \mathrm{c} ; \mathrm{C} .55$

Nima Gharibi

Numerade Educator

Problem 66

Explain why $A$ is a stable compound but $B$ is not.
A
B

Ian Kaigh

Numerade Educator

Problem 67

Alkene A can be isomerized to isocomene, a natural product isolated from goldenrod, by treatment with TsOH. Draw a stepwise mechanism for this conversion. (Hint: Look for a carbocation rearrangement.)

Ian Kaigh

Numerade Educator

Problem 68

Lactones, cyclic esters such as compound $A,$ are prepared by halolactonization, an addition reaction to an alkene. For example, iodolactonization of B forms lactone $\mathrm{C},$ a key intermediate in the synthesis of prostaglandin $\mathrm{PGF}_{2 \alpha}$ (Section 4.15 ). Draw a stepwise mechanism for this addition reaction.

Madeline Currie

Madeline Currie

Numerade Educator

Problem 69

Draw a stepwise mechanism for the following reaction.

Colton K

Numerade Educator

Problem 70

Like other electrophiles, carbocations add to alkenes to form new carbocations, which can then undergo substitution or elimination reactions depending on the reaction conditions. With this in mind, draw a stepwise mechanism for the following reaction, which involves the addition of an electrophile-a carbocation-to a double bond.

Ian Kaigh

Numerade Educator

Problem 71

Draw a stepwise mechanism for the following reaction. This reaction combines two processes: the opening of an epoxide ring with a nucleophile and the addition of an electrophile to a carbon-carbon double bond. (Hint: Begin the mechanism by protonating the epoxide ring.)

Ian Kaigh

Numerade Educator