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.