Textbook Question
Provide the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HBr, H2O2.
(e)
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Ch. 8 - Alkenes I: Properties and Electrophilic Additions
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
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Mullins 1st EditionCh. 8 - Alkenes I: Properties and Electrophilic AdditionsProblem 37b
Mullins 1st EditionCh. 8 - Alkenes I: Properties and Electrophilic AdditionsProblem 37bChapter 7, Problem 37b
Which reagent system (HBr or HBr, H2O2) would you use to carry out the following transformations?
(b) 
Verified step by step guidance1
Identify the type of reaction: The problem involves the addition of HBr to an alkene, which can proceed via two different mechanisms depending on the presence of peroxides.
Understand the role of reagents: HBr alone will add to an alkene following Markovnikov's rule, where the hydrogen atom attaches to the less substituted carbon, and the bromine attaches to the more substituted carbon.
Consider the effect of peroxides: When HBr is used in the presence of peroxides (H₂O₂), the reaction follows an anti-Markovnikov addition. This means the bromine atom will attach to the less substituted carbon, and the hydrogen will attach to the more substituted carbon.
Analyze the desired product: Determine whether the transformation requires a Markovnikov or anti-Markovnikov addition by examining the position of the bromine in the target molecule.
Select the appropriate reagent system: Based on the desired product, choose HBr for Markovnikov addition or HBr with H₂O₂ for anti-Markovnikov addition.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Markovnikov's Rule
Markovnikov's Rule states that in the addition of HX to an alkene, the hydrogen atom will attach to the carbon with more hydrogen atoms, while the halide (X) will attach to the carbon with fewer hydrogen atoms. This rule helps predict the major product in electrophilic addition reactions.
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The 18 and 16 Electron Rule
Anti-Markovnikov Addition
Anti-Markovnikov addition occurs when the addition of HX to an alkene results in the halide attaching to the less substituted carbon. This is typically observed in the presence of peroxides (H₂O₂) with HBr, where the reaction proceeds via a radical mechanism, leading to the opposite regioselectivity compared to Markovnikov's Rule.
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02:43Anti-Markovnikov addition of alcohols to terminal alkynes yields aldehydes
Radical Mechanism
A radical mechanism involves the formation of free radicals, which are highly reactive species with unpaired electrons. In the presence of peroxides, HBr can initiate a radical chain reaction, leading to anti-Markovnikov addition. Understanding this mechanism is crucial for predicting the outcome of reactions involving radical initiators.
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03:28The mechanism of Radical Polymerization.
Related Practice
Textbook Question
Radical addition to alkenes is not effective for the synthesis of iodo- and chloroalkanes. Using your knowledge of the mechanism of this reaction, along with bond dissociation energies, explain why the radical additions of HI and HCl are not effective. (Assume ∆H = 65 kcal/ mol for the C–C π bond.)
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Textbook Question
Which reagent system (HBr or HBr, H2O2) would you use to carry out the following transformations?
(a)
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Textbook Question
Which reagent system (HBr or HBr, H2O2) would you use to carry out the following transformations?
(c)
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Textbook Question
Provide the expected product for the reaction of each of the following alkenes with H2SO4 and H2O.
(a)
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Textbook Question
Provide an arrow-pushing mechanism that rationalizes the formation of each of the products you predicted in Assessment 8.35 (ii). Make sure your mechanism accounts for all products formed, including stereoisomers and regioisomers, where applicable.