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Organic Chemistry

Marc Loudon, Jim Parise

Chapter 4

Introduction to Alkenes. Structure and Reactivity - all with Video Answers

Educators

Chapter Questions

05:33

Problem 1

Arrange the labeled bonds in the following molecule in order of increasing length, shortest first. Explain your reasoning.

Kevin Barayuga
Kevin Barayuga
Numerade Educator
06:14

Problem 2

Which of the following alkenes can exist as double-bond stereoisomers? Identify the stereocenters in each.
(a) $\mathrm{H}_{2} \mathrm{C}=\mathrm{CHCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}$
(b) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CHCH}_{2} \mathrm{CH}_{3}$
(c) $\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{3}$
(d) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CCH}_{3}$

Kevin Barayuga
Kevin Barayuga
Numerade Educator
06:37

Problem 3

Give the structure for each of the following:
(a) 2-methylpropene
(b) 4 -methyl-1,3-hexadiene
(c) 1-isopropenylcyclopentene
(d) $5-(3$ -pentenyl)- 1,3,6,8 -decatetraene

Kevin Barayuga
Kevin Barayuga
Numerade Educator
05:51

Problem 4

Name the following compounds. Ignore double-bond stereochemistry.

Kevin Barayuga
Kevin Barayuga
Numerade Educator
04:38

Problem 5

Name each of the following compounds, including the proper designation of the double-bond stereochemistry:

Kevin Barayuga
Kevin Barayuga
Numerade Educator
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Problem 6

Give the structure of:
(a) $(E)-4$ -allyl-1,5-octadiene
(b) $(2 E, 7 Z)-5-[(E)-1$ -propenyl $]-2,7$ -nonadiene
Be sure to read Study Guide Link 4.2 if you have difficulty with this problem.

Kaden Bunch
Kaden Bunch
Numerade Educator
01:15

Problem 7

In each case, which group receives the higher priority?

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
01:33

Problem 8

Calculate the unsaturation number for each of the formulas in parts (a) and (b) and each of the compounds in parts (c) and (d). [Try to work parts (c) and (d) using only the compound names.]
(a) $\mathrm{C}_{3} \mathrm{H}_{4} \mathrm{Cl}_{4}$
(b) $\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{~N}_{2}$
(c) methylcyclohexane
(d) 2,4,6 -octatriene

Ronald Prasad
Ronald Prasad
Numerade Educator
02:37

Problem 9

A compound has the molecular formula $\mathrm{C}_{20} \mathrm{H}_{34} \mathrm{O}_{2} .$ Certain structural evidence suggests that the compound contains two methyl groups and no carbon-carbon double bonds. Give one structure consistent with these findings in which all rings are six-membered. (Many structures are possible.)

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
04:34

Problem 10

Which of the following cannot be correct formula(s) for an organic compound? Explain.
$\begin{array}{ccccc}\text { (a) } \mathrm{C}_{10} \mathrm{H}_{20} \mathrm{~N}_{3} & \mathrm{C}_{10} \mathrm{H}_{20} \mathrm{~N}_{2} \mathrm{O}_{2} & \mathrm{C}_{10} \mathrm{H}_{27} \mathrm{~N}_{3} \mathrm{O}_{2} & \mathrm{C}_{10} \mathrm{H}_{16} \mathrm{O}_{2} \\ A & B & C & D\end{array}$
(b) Draw constitutional isomers of compounds with the formula $\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}$ that contain
(1) an alcohol functional group;
(2) a ketone functional group.

Mystique Till
Mystique Till
Numerade Educator
02:34

Problem 11

Which compound in each set should have the larger dipole moment? Explain.
(a) cis-2-butene or trans-2-butene
(b) propene or 2 -methylpropene

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
01:15

Problem 12

Which of the following two carboxylic acids is more acidic? Explain.

Raghvendra Singh
Raghvendra Singh
Numerade Educator
01:57

Problem 13

(a) Calculate the enthalpy change for the hypothetical reaction 1-butene $\longrightarrow 2$ -methylpropene. The heats of formation are 1-butene, $-0.30 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(-0.07 \mathrm{kcal} \mathrm{mol}^{-1}\right) ; 2$ methylpropene, $-17.3 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(-4.13 \mathrm{kcal} \mathrm{mol}^{-1}\right)$.
(b) Which butene isomer in part (a) is more stable?

Hunza Gilgit
Hunza Gilgit
Numerade Educator
05:19

Problem 14

(a) If the standard enthalpy change for the reaction 2 -ethyl-1-butene $\longrightarrow 1$ -hexene is $+15.3 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(+3.66 \mathrm{kcal} \mathrm{mol}^{-1}\right),$ and if $\Delta H_{\mathrm{f}}^{\circ}$ for 1 -hexene is $-40.5 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(-9.68 \mathrm{kcal} \mathrm{mol}^{-1}\right),$ what is $\Delta H_{\mathrm{f}}^{\circ}$ for 2 -ethyl-1-butene?
(b) Which isomer in part (a) is more stable?

Muhammad Ahsan
Muhammad Ahsan
Numerade Educator
03:58

Problem 15

The $\Delta H_{\mathrm{f}}^{\circ}$ of $\mathrm{CO}_{2}$ is $-393.51 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(-94.05 \mathrm{kcal} \mathrm{mol}^{-1}\right)$, and the $\Delta H_{\mathrm{f}}^{\circ}$ of $\mathrm{H}_{2} \mathrm{O}$ is $-285.83 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(-68.32 \mathrm{kcal} \mathrm{mol}^{-1}\right) .$ Cal-
culate the $\Delta H_{\mathrm{f}}^{\circ}$ of 1-heptene from its heat of combustion, $-4693.1 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(-1121.7 \mathrm{kcal} \mathrm{mol}^{-1}\right) .$ (See Further Exploration 4.2.)

Temi Ajayi
Temi Ajayi
Numerade Educator
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Problem 16

Within each series arrange the compounds in order of increasing stability:

Colton K
Colton K
Numerade Educator
01:14

Problem 17

Alkenes can undergo the addition of hydrogen in the presence of certain catalysts. (You will study this reaction in Sec. $4.9 \mathrm{~A}$.)
The $\Delta H^{\circ}$ of this reaction, called the enthalpy of hydrogenation, can be measured very accurately and can serve as a source of heats of formation. Consider the following enthalpies of hydrogenation: $(E)-3$ -hexene, $-117.9 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(28.2 \mathrm{kcal} \mathrm{mol}^{-1}\right)$;
(Z)-3-hexene, $-121.6 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(29.1 \mathrm{kcal} \mathrm{mol}^{-1}\right)$. Calculate the heats of formation of these two alkenes, given that the $\Delta H_{\mathrm{f}}^{\circ}$ of hexane is $-167.2 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(40.0 \mathrm{kcal} \mathrm{mol}^{-1}\right)$.

Sriparna Bhattacharjee
Sriparna Bhattacharjee
Numerade Educator
06:37

Problem 18

Give the structure of the addition product formed when ethylene reacts with each of the following reagents:
(a) $\mathrm{H}-\mathrm{I}$
(b) $\mathrm{Br}_{2}$
(c) $\mathrm{BH}_{3}$ (Hint: Each of the $\mathrm{B}-\mathrm{H}$ bonds undergoes an addition to one molecule of ethylene. That is, three moles of ethylene react with one mole of $\mathrm{BH}_{3}$.)

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
04:27

Problem 19

Using the known regioselectivity of hydrogen halide addition to alkenes, predict the addition product that results from the reaction of:
(a) $\mathrm{H}-\mathrm{Cl}$ with 2 -methylpropene
(b) $\mathrm{H}-\mathrm{Br}$ with 1 -methylcyclohexene

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
04:29

Problem 20

Classify the isomeric carbocations in each of the following parts as primary, secondary, or tertiary, and tell which is the most stable carbocation in each part and why.

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
04:29

Problem 21

Classify the isomeric carbocations in each of the following parts as primary, secondary, or tertiary, and tell which is the most stable carbocation in each part and why.

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
07:09

Problem 22

In each case, give $t$ wo different alkene starting materials that would react with $\mathrm{H}-\mathrm{Br}$ to give the compound shown as the major (or only) addition product.

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
05:11

Problem 23

Which of the following carbocations is likely to rearrange? If rearrangement occurs, give the structures of the rearranged carbocations.

Temi Ajayi
Temi Ajayi
Numerade Educator
07:14

Problem 24

Draw curved-arrow mechanisms and transition-state structures for each of the following two reactions. Each reaction occurs as a single step.
(a) $\mathrm{CH}_{3} \mathrm{CH}_{2}-\ddot{\mathrm{Br}}:+\mathrm{FOOCH}_{3} \longrightarrow \mathrm{CH}_{3} \mathrm{CH}_{2}-\mathrm{O} \mathrm{CH}_{3}+: \ddot{\mathrm{Br}}:$
(b) $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\ddot{\mathrm{Br}}: \longrightarrow\left(\mathrm{CH}_{3}\right)_{3} \stackrel{+}{\mathrm{C}}+\ddot{\mathrm{Br}}^{-}$

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
07:16

Problem 25

"Only one of the following three alkyl halides can be prepared as the major product of the addition of HBr to an alkene. Which compound can be prepared in this way? Explain why the other two cannot be prepared in this way.
(a) (DIAGRAM CAN'T COPY)
(b) (DIAGRAM CAN'T COPY)
(c) (DIAGRAM CAN'T COPY)
"

Julia G.
Julia G.
Numerade Educator

Problem 26

"Draw curved-arrow mechanisms and transition-state structures for each of the following two reactions. Each reaction occurs as a single step.
(a)
(b) $\left(\mathrm{CH}_3\right)_3 \mathrm{C}-\ddot{\mathrm{Br}}: \longrightarrow\left(\mathrm{CH}_3\right)_3 \stackrel{+}{\mathrm{C}}+\ddot{\mathrm{Br}}:$"

Check back soon!
07:05

Problem 27

(a) Draw the transition state for the reverse reaction of Eq. $4.30 .$ Compare it with the transition state shown in Eq. 4.31 .
(b) What general statement can you make about the transition-state structures for a reaction and its reverse?

Preeti Kumari
Preeti Kumari
Numerade Educator
00:57

Problem 28

(a) The standard free energy of activation of one reaction $A$ is $90 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(21.5 \mathrm{kcal} \mathrm{mol}^{-1}\right)$. The standard free energy of activation of another reaction $B$ is $75 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(17.9 \mathrm{kcal} \mathrm{mol}^{-1}\right)$. Which reaction is faster and by what factor? Assume a temperature of $298 \mathrm{~K}$.
(b) Estimate how much you would have to increase the temperature of the slower reaction so that it would have a rate equal to that of the faster reaction.

Aadit Sharma
Aadit Sharma
Numerade Educator
00:57

Problem 29

The standard free energy of activation of a reaction $A$ is $90 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(21.5 \mathrm{kcal} \mathrm{mol}^{-1}\right)$ at $298 \mathrm{~K}$. Reaction $B$ is one million times faster than reaction $A$ at the same temperature. The products of each reaction are $10 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(2.4 \mathrm{kcal} \mathrm{mol}^{-1}\right)$ more stable than the reactants.
(a) What is the standard free energy of activation of reaction $B$ ?
(b) Draw reaction free-energy diagrams for the two reactions showing the two values of $\Delta G^{\circ}$ to scale.
(c) What is the standard free energy of activation of the reverse reaction in each case?

Aadit Sharma
Aadit Sharma
Numerade Educator
02:33

Problem 30

Draw a reaction free-energy diagram for a reaction $A \rightleftarrows B \rightleftarrows C$ that meets the following criteria: The standard free energies are in the order $C<A<B$, and the rate-limiting step of the reaction is $B \rightleftarrows C$.

Niamat Khuda
Niamat Khuda
Numerade Educator
00:33

Problem 31

Repeat Problem 4.30 for a case in which the standard free energies are in the order $A<C<B$, and the rate-limiting step of the reaction is $A \rightleftarrows B$.

Nicole Smina
Nicole Smina
Numerade Educator
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Problem 32

Apply Hammond's postulate to decide which reaction is faster: addition of $\mathrm{HBr}$ to 2 -methylpropene or addition of $\mathrm{HBr}$ to trans2 -butene. Assume that the energy difference between the starting alkenes can be ignored. Why is this assumption necessary?

Lainey Roebuck
Lainey Roebuck
Numerade Educator
01:45

Problem 33

Give the product formed when each of the following alkenes reacts with a large excess of hydrogen in the presence of $\mathrm{Pd} / \mathrm{C}$.
(a) 1-pentene
(b) $(E)-1,3$ -hexadiene

Grigoriy Sereda
Grigoriy Sereda
Numerade Educator
05:17

Problem 34

(a) Give the structures of five alkenes, each with the formula $\mathrm{C}_{6} \mathrm{H}_{12}$, that would give hexane as the product of catalytic hydrogenation.
(b) How many alkenes containing one double bond can react with $\mathrm{H}_{2}$ over a $\mathrm{Pt} / \mathrm{C}$ catalyst to give methylcyclopentane? Give their structures..

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
View

Problem 35

Give the mechanism for the reaction in Eq. $4.43 .$ Show each step of the mechanism separately with careful use of the curvedarrow notation. Explain why the rearrangement takes place.

Lainey Roebuck
Lainey Roebuck
Numerade Educator
02:23

Problem 36

The alkene 3,3 -dimethyl-1-butene undergoes acid-catalyzed hydration with rearrangement. Use the mechanism of hydration and rearrangement to predict the structure of the hydration product of this alkene.

Nicholas Sacco
Nicholas Sacco
Numerade Educator
02:50

Problem 37

(a) Unlike the alcohol product Eq. 4.41 , the product in Eq. 4.43 does not come to equilibrium with the starting alkene. However, it does come to equilibrium with two other alkenes. What are their structures?
(b) Why isn't the alkene starting material in Eq. 4.43 part of the equilibrium mixture?

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
03:05

Problem 38

Explain why the hydration of ethylene (Eq 4.44) is a very slow reaction. (Hint: Think about the structure of the reactive intermediate and apply Hammond's postulate.)

Sydney Atkins
Sydney Atkins
Numerade Educator
03:16

Problem 39

Isopropyl alcohol is produced commercially by the hydration of propene. Show the mechanistic steps of this process. If you do not know the structure of isopropyl alcohol, try to deduce it by analogy from the structure of propene and the mechanism of alkene hydration.

Nicholas Sacco
Nicholas Sacco
Numerade Educator
08:18

Problem 40

Give the structures and IUPAC substitutive names of the isomeric alkenes with molecular formula $\mathrm{C}_{6} \mathrm{H}_{12}$ containing five carbons in their principal chains.

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
07:30

Problem 41

Give the structures and the IUPAC substitutive names of the isomeric alkenes with the molecular formula $\mathrm{C}_{6} \mathrm{H}_{12}$ containing four carbons in their principal chain.

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
02:39

Problem 42

Which alkenes in Problem 4.41 give predominantly a single constitutional isomer when treated with $\mathrm{HBr}$, and which give a mixture of isomers? Explain.

Dalton Hilovsky
Dalton Hilovsky
Numerade Educator
06:03

Problem 43

Arrange the alkenes in Problem 4.40 in order of increasing heats of formation. (Some may be classified as "about the same.")

Lashan De Silva
Lashan De Silva
University of Houston
04:17

Problem 44

Give a structure for each of the following compounds.
(a) cyclobutene
(b) 3 -methyl-1-octene
(c) 5,5 -dimethyl- 1,3 -cycloheptadiene
(d) 1 -vinylcyclohexene

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
02:26

Problem 45

Give an IUPAC substitutive name for each of the following compounds. Include the $E, Z$ designations where appropriate.

Aadit Sharma
Aadit Sharma
Numerade Educator
05:52

Problem 46

A confused chemist Al Keane used the following names in a paper about alkenes. Although each name specifies a structure, in some cases the name is incorrect. Correct the names that are wrong.
(a) 3 -butene
(b) trans-1-tert-butylpropene
(c) $(Z)-2$ -hexene
(d) 6 -methylcycloheptene

Kaitlynn Wade
Kaitlynn Wade
Numerade Educator
02:49

Problem 47

Specify the configuration $(E$ or $Z)$ of each of the following alkenes. Note that $\mathrm{D}$ is deuterium, or ${ }^{2} \mathrm{H},$ the isotope of hydrogen with atomic mass $=2$.

Susan Hallstrom
Susan Hallstrom
Numerade Educator
02:34

Problem 48

Classify the compounds within each of the following pairs as either identical molecules (I), constitutional isomers (C), stereoisomers (S), or none of the above (N).
(a) cyclohexane and 1-hexene
(b) cyclopentane and cyclopentene

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
04:55

Problem 49

Use the principles of Sec. $1.3 \mathrm{~B}$ to predict the geometry of $\mathrm{BF}_{3}$. What hybridization of boron is suggested by this geometry? Draw an orbital diagram for hybridized boron similar to that for the carbons in ethylene shown in Fig. 4.3 (p. 127), and provide a hybrid orbital description of the bonding in $\mathrm{BF}_{3}$.

ES
Eugene Schneider
University of Minnesota - Twin Cities
04:43

Problem 50

Classify each of the labeled bonds in the following structure in terms of the bond type ( $\sigma$ or $\pi$ ) and the component orbitals that overlap to form the bond. (For example, the carbon-carbon bond in ethane is an $s p^{3}-s p^{3} \sigma$ bond.)

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
01:00

Problem 51

(a) The following compound can be prepared by the addition of HBr to either of two alkenes; give their structures.
(b) Starting with the same two alkenes, would the products be different if DBr were used? Explain. (See note about deuterium in Problem 4.47.)

Lottie Adams
Lottie Adams
Numerade Educator
06:50

Problem 52

Give the structures of all the alkenes containing one double bond that would give propylcyclohexane as the product of catalytic hydrogenation.

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
05:33

Problem 53

An alkene $X$ with molecular formula $\mathrm{C}_{7} \mathrm{H}_{12}$ adds HBr to give a single alkyl halide $Y$ with molecular formula $\mathrm{C}_{7} \mathrm{H}_{13} \mathrm{Br}$ and undergoes catalytic hydrogenation to give 1,1-dimethylcyclopentane. Draw the structures of $X$ and $Y$.

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
05:17

Problem 54

Give the structures of the two stereoisomeric alkenes with the molecular formula $\mathrm{C}_{6} \mathrm{H}_{12}$ that react with HI to give the same single product and undergo catalytic hydrogenation to give hexane.

Anupa Sharad Medhekar
Anupa Sharad Medhekar
Numerade Educator
04:18

Problem 55

You have been called in as a consultant for the firm Alcohols Unlimited, which wants to build a plant to produce 3 -methyl-I-butanol, $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCH}_{2} \mathrm{CH}_{2} \mathrm{OH}$. The research director, Al Keyhall, has proposed that acid-catalyzed hydration of 3 -methyl-1-butene be used to prepare this compound. The company president, O. H. Gruppa, has asked you to evaluate this suggestion. Millions of dollars are on the line. What is your answer? Can 3 -methyl-1-butanol be prepared in this way? Explain your answer.

Madeline Currie
Madeline Currie
Numerade Educator
02:02

Problem 56

A certain compound $A$ is converted into a compound $B$ in a reaction without intermediates. The reaction has an equilibrium constant $K_{\text {eq }}=[B] /[A]=150$ and, with the free energy of $A$ as a reference point, a standard free energy of activation of $96 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(23 \mathrm{kcal} \mathrm{mol}^{-1}\right)$.
(a) Draw a reaction free-energy diagram for this process, showing the relative free energies of $A, B,$ and the transition state for the reaction.
(b) What is the standard free energy of activation for the reverse reaction $B \rightarrow A$ ? How do you know?

Aadit Sharma
Aadit Sharma
Numerade Educator
02:08

Problem 57

A reaction $A \rightleftarrows B \rightleftarrows C \rightleftarrows D$ has the reaction free-energy diagram shown in Fig. $\mathrm{P} 4.57$.
(a) Which compound is present in greatest amount when the reaction comes to equilibrium? In least amount?
(b) What is the rate-limiting step of the reaction?
(c) Using a vertical arrow, label the standard free energy of activation for the overall $A \rightarrow D$ reaction.
(d) Which reaction of compound $C$ is faster: $C \rightarrow B$ or $C \rightarrow D ?$ How do you know?

Aadit Sharma
Aadit Sharma
Numerade Educator
01:54

Problem 58

Invoking Hammond's postulate, draw the structure of the reactive intermediate that should most closely resemble the transition state of the rate-limiting step for the hydration of 1-methylcyclohexene. (The first step in the mechanism. protonation of the double bond, is rate-limiting.)

David Collins
David Collins
Numerade Educator
00:46

Problem 59

(a) Give the product $X$ expected when methylenecyclobutane undergoes acid-catalyzed hydration.
(b) The rate-limiting step is protonation of the double bond; use $\mathrm{H}_{3} \mathrm{O}^{+}$ as the acid catalyst. Draw the structure of the reactive intermediate formed in the rate-limiting step.
(c) Draw the transition state for the rate-limiting step.
(d) What is the rate-limiting step for dehydration of $X$ (the reverse of the reaction shown above)?

Dalton Hilovsky
Dalton Hilovsky
Numerade Educator
01:57

Problem 60

The heat of formation of $(E)-1,3$ -pentadiene is $75.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$ (18. I kcal mol $^{-1}$ ), and that of 1,4 -pentadiene is $106.3 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(25.4 \mathrm{kcal} \mathrm{mol}^{-1}\right)$
(a) Which alkene has the more stable arrangement of bonds?
(b) Calculate the heat liberated when one mole of 1,3 pentadiene is burned. The heat of combustion of carbon is $-393.5 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(-94.05\right.$ keal $\left.\mathrm{mol}^{-1}\right),$ and that of $\mathrm{H}_{2}$
is $-285.8 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(-68.32 \mathrm{kcal} \mathrm{mol}^{-1}\right)$

Hunza Gilgit
Hunza Gilgit
Numerade Educator
01:14

Problem 61

The $\Delta H^{\circ}$ of hydrogenation is the heat liberated when a compound undergoes catalytic hydrogenation. Consider the $\Delta H^{\circ}$ values for hydrogenation of the following three alkenes: 3 -methyl-l-butene, $-126.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$ $\left(-30.3\right.$ kcal $\left.\mathrm{mol}^{-1}\right) ; 2$ -methyl-1-butene, $-119.2 \mathrm{~kJ} \mathrm{~mol}^{-1}$
$\left(-28.5 \mathrm{kcal} \mathrm{mol}^{-1}\right) ;$ and 2 -methyl-2-butene, $-112.6 \mathrm{~kJ} \mathrm{~mol}^{-1}$
$\left(-26.9\right.$ kcal $\left.\mathrm{mol}^{-1}\right)$
(a) Draw an energy diagram in which the three alkanes are placed on the same energy seale along with 2-methylbutane.
(b) Use these data to rank the three alkenes in order of stability, most stable first. Explain how you reached your conclusion.
(c) By how much do the heats of formation of the three alkenes differ? Explain.
(d) Explain why this stability order is expected.

Sriparna Bhattacharjee
Sriparna Bhattacharjee
Numerade Educator
01:51

Problem 62

Make a model of cycloheptene with the trans (or $E$ ) configuration at the double bond. Now make a model of cis-cycloheptene. By examining your models, determine which compound should have the greater heat of formation. Explain.

Sydney Atkins
Sydney Atkins
Numerade Educator
01:17

Problem 63

Consider the following compounds and their dipole moments:
Assume that the $\mathrm{C}-\mathrm{Cl}$ bond dipole is oriented as follows in each of these compounds.
(a) According to the preceding dipole moments, which is more electron-donating toward a double bond, methyl or hydrogen? Explain..
(b) Which of the following compounds should have the greater dipole moment? Explain.

Lottie Adams
Lottie Adams
Numerade Educator
02:02

Problem 64

Supply the curved-arrow notation for the acid-catalyzed isomerization shown in Fig. $\mathrm{P} 4.64 .$

Crystal Wang
Crystal Wang
Numerade Educator
03:48

Problem 65

The curved-arrow notation can be used to understand seemingly new reactions as simple extensions of what you already know. This is the first step in developing an ability to use the notation to predict new reactions. Provide a curved-arrow mechanism for the following reaction.
To do this, follow these steps:
I. Examine the reactants and products and label corresponding atoms. If you're not sure, make a guess.
2. Describe what has happened to the functional groups in the starting material. In this case, focus on the double bond. Is this transformation similar in any way to a reaction you have seen before?
3. Make the connections you deduced in (1) with a curved-arrow mechanism, trying to use steps that are similar to mechanistic steps you've seen in other reactions. Use separate structures for each step of the mechanism; that is, don't try to write several mechanistic steps using the same structure.
4. Use a Lewis acid-base association, Lewis acid-base dissociation, or Bronsted acid-base reaction for each step.

Crystal Wang
Crystal Wang
Numerade Educator
02:41

Problem 66

The industrial synthesis of methyl tert-butyl ether involves treatment of 2 -methylpropene with methanol $\left(\mathrm{CH}_{3} \mathrm{OH}\right)$ in the presence of an acid catalyst, as shown in the following equation.
This ether is used commercially as an antiknock gasoline additive. Using the curved-arrow notation, propose a mechanism for this reaction.

Niamat Khuda
Niamat Khuda
Numerade Educator
01:10

Problem 67

Using the curved-arrow notation, suggest a mechanism for the reaction shown in Fig. $\mathrm{P} 4.67$.

Arun Bana
Arun Bana
Numerade Educator
02:54

Problem 68

The standard free energy of formation, $\Delta G_{\mathrm{f}}^{\mathrm{o}}$, is the freeenergy change for the formation of a substance at $25^{\circ} \mathrm{C}$ and 1 atm pressure from its elements in their natural states under the same conditions.
(a) Calculate the equilibrium constant for the interconversion of the following alkenes, given the standard free energy of formation of each. Indicate which compound is favored at equilibrium.
(b) What does the equilibrium constant tell us about the rate at which this interconversion takes place?

Sriparna Bhattacharjee
Sriparna Bhattacharjee
Numerade Educator
03:11

Problem 69

The difference in the standard free energies of formation for 1 -butene and 2 -methylpropene is $13.4 \mathrm{~kJ} \mathrm{~mol}^{-1}$ (3.2 kcal mol $^{-1}$ ). (See the previous problem for a definition of $\Delta G_{\mathrm{f}}^{\mathrm{o}}$ )
(a) Which compound is more stable? Why?
(b) The standard free energy of activation for the hydration of 2 -methylpropene is $22.8 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(5.5 \mathrm{kcal} \mathrm{mol}^{-1}\right)$ less
than that for the hydration of 1 -butene. Which hydration reaction is faster?
(c) Draw reaction free-energy diagrams on the same scale for the hydration reactions of these two alkenes, showing the relative free energies of both starting materials and rate-determining transition states.
(d) What is the difference in the standard free energies of the transition states for the two hydration reactions? Which transition state has lower energy? Using the mechanism of the reaction, suggest why it is more stable.

Lottie Adams
Lottie Adams
Numerade Educator
03:33

Problem 70

The standard free energy of activation $\left(\Delta G^{\circ}{ }^{\dagger}\right)$ for hydration of 2 -methylpropene to 2 -methyl-2-propanol (Eq. 4.41 , p. 173 ) is $91.3 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(21.8 \mathrm{kcal} \mathrm{mol}^{-1}\right)$. The standard
free energy $\Delta G^{\circ}$ for hydration of 2 -methylpropene is $-5.56 \mathrm{~kJ} \mathrm{~mol}^{-1}\left(-1.33 \mathrm{kcal} \mathrm{mol}^{-1}\right)$. The rate of hydration
of methylenecyclobutane to give an alcohol (compound $X$ in Problem 4.59 ) is 0.6 times the rate of hydration of 2 -methylpropene. The equilibrium constant for the hydration of methylenecyclobutane is about 250 times greater (in favor of hydration) than the equilibrium constant for the hydration of 2 -methylpropene. Which alcohol, $X$ or 2 -methyl-2-propanol, undergoes dehydration faster, and how much faster? Explain.

John Nicolle
John Nicolle
Numerade Educator