Study Guide: Chapter 04: Free-Radical Reactions
I.
Properties and Energies of Free-Radicals
Learning Objectives
1. Describe the shape, hybridization, and charge of a carbon free-radical.
2. Use the Bond Dissociation Energies table to calculate the ΔH of a given chemical reaction.
3. Use the Bond Dissociation Energies table to predict the relative stability of carbon radicals.
Study Activities
1. Watch the lecture videos and review the notes.
2. Read textbook sections.
3. Practice ΔH calculation of chemical reactions problems.
Section I Practice Problems
• Using the table of homolytic bond dissociation energies provided in the notes, calculate ΔH for the following reactions.
CH04-SQ1
CH3
CH 3
Br2
+
CH3
CH 2
Br
+
HBr
CH04-SQ2
Cl
CH3
CH
CH3
+
Cl2
CH 3
C
CH 3
CH3
I
OH
CH 3
+
HCl
CH 3
+
HI
CH04-SQ3
CH 3
C
CH3
+
H2 O
CH3
CH3
II.
C
CH 3
Free-Radical Halogenation Reaction
Learning Objectives
1. Predict the preferred products of a Free-Radical Halogenation reaction, including connectivity, regiochemistry, and
stereochemistry.
2. Provide a stepwise mechanism for a given Free-Radical Halogenation reaction.
3. Provide a reactant and reagents required to make a given target using a Free-Radical Halogenation reaction.
4. Describe and explain the difference in regioselectivity between chlorine (Cl2) and bromine (Br2).
Study Activities
1. Watch the lecture videos and review the notes.
2. Read the textbook sections.
3. Make flashcards of the observed reaction for Free-Radical Halogenation.
4. Practice Predict the Product problems.
5. Practice mechanism problem.
6. Practice synthesis problems.
© 2022 Dr. Thomas Mucciaro. All rights reserved.
Chem A220/A225
Study Guide: Chapter 04: Free-Radical Reactions
Page 2
Section II Practice Problems
• Predict the Products: Complete the following reactions by writing the preferred product(s) formed. More than one
preferred product may be formed in some cases. Show stereochemistry where appropriate, and draw all enantiomers of
any chiral compounds.
CH04-SQ4
CH3
CH2
CH04-SQ5
Br2
CH 3
CH3
Δ or hν
CH04-SQ6
CH2
Cl2
CH 3
Δ or hν
CH04-SQ7
Br2
CH3
Cl2
CH 3
Δ or hν
Δ or hν
(ignore stereochem)
CH04-SQ8
•
CH04-SQ9
Br2
Br2
Δ or hν
Δ or hν
Propose a complete mechanism for the following reaction. Show all intermediates with formal charges and lone pairs,
draw all important resonance structures, and use arrows to show the movement of electrons. Label all initiation and
propagation steps, and propose one termination step.
CH04-SQ10
H
CH3
C
CH3
CH3
Δ or hν
CH3
•
Br
Br2
C
CH3
CH3
(+ HBr)
(byproduct)
Provide a reactant and reagents required to make each of the following targets using a Free-Radical Halogenation
reaction. If the target cannot be made with a Free-Radical Halogenation, write “Not Possible.”
CH04-SQ11
CH04-SQ12
Cl
CH04-SQ13
Br
CH 3
CH
CH04-SQ14
CH 2
Br
Cl
CH3
© 2022 Dr. Thomas Mucciaro. All rights reserved.
Chem A220/A225
III.
Study Guide: Chapter 04: Free-Radical Reactions
Page 3
Hydrogen Bromide Addition to Alkenes
Learning Objectives
1. Predict the preferred products of a Hydrogen Bromide Addition to Alkenes reaction without and with peroxide,
including connectivity, regiochemistry, and stereochemistry.
2. Provide a stepwise mechanism for a given Hydrogen Bromide Addition to Alkenes with peroxide reaction.
3. Provide a reactant and reagents required to make a given target using an Hydrogen Bromide Addition to Alkenes
reaction without and with peroxide.
Study Activities
1. Watch the lecture videos and review the notes.
2. Read the textbook sections.
3. Review the notes and videos for the Hydrogen Bromide Addition to Alkenes reaction from A220.
4. Make flashcards of the observed reaction for Hydrogen Bromide Addition to Alkenes reaction without and with
peroxide.
5. Practice Predict the Product problems.
6. Practice mechanism problem.
7. Practice synthesis problems.
Section III Practice Problems
• Predict the Products: Complete the following reactions by writing the preferred product(s) formed. More than one
preferred product may be formed in some cases. Show stereochemistry where appropriate, and draw all enantiomers of
any chiral compounds.
CH04-SQ15
CH3
CH04-SQ16
C
CH2
HBr
(no peroxides)
CH3
CH04-SQ17
CH04-SQ18
CH3
C
HBr
peroxide
CH2
CH3
CH3
CH 3
C
CH
CH2
HBr
(no peroxides)
CH3
CH 3
CH3
C
CH
CH 2
HBr
peroxide
CH 3
CH04-SQ19
CH04-SQ20
HBr
(no peroxides)
CH04-SQ21
HBr
peroxide
CH04-SQ22
CH 2
HBr
(no peroxides)
CH 2
HBr
peroxide
© 2022 Dr. Thomas Mucciaro. All rights reserved.
Chem A220/A225
•
Study Guide: Chapter 04: Free-Radical Reactions
Page 4
Propose a complete mechanism for the following reaction. Show all intermediates with formal charges and lone pairs,
draw all important resonance structures, and use arrows to show the movement of electrons. Label all initiation and
propagation steps, and propose one termination step.
CH04-SQ23
CH 3
C
CH
CH 3
CH3
•
HBr
H2O2
CH3
H
Br
C
CH
CH3
CH3
Provide a reactant and reagents required to make each of the following targets using a Hydrogen Bromide Addition to
Alkenes reaction.
CH04-SQ24
CH04-SQ25
Br
CH04-SQ26
Br
CH3
Br
© 2022 Dr. Thomas Mucciaro. All rights reserved.