Textbook Question
Provide the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HBr, H2O2
(b)
843
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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
Chapter 7, Problem 33
Would you expect but-2-ene or 2-methylbut-2-ene to react more quickly with HBr?
Verified step by step guidance1
Identify the type of reaction: Both but-2-ene and 2-methylbut-2-ene will undergo an electrophilic addition reaction with HBr, where the alkene reacts with the hydrogen bromide to form a bromoalkane.
Consider the stability of the carbocation intermediate: In electrophilic addition reactions, the alkene forms a carbocation intermediate. The stability of this carbocation is crucial in determining the rate of the reaction.
Analyze the structure of but-2-ene: When but-2-ene reacts with HBr, it forms a secondary carbocation. Secondary carbocations are relatively stable, but not as stable as tertiary carbocations.
Analyze the structure of 2-methylbut-2-ene: When 2-methylbut-2-ene reacts with HBr, it forms a tertiary carbocation due to the presence of the methyl group, which provides additional stabilization through hyperconjugation and inductive effects.
Compare the stability of the carbocations: Tertiary carbocations are more stable than secondary carbocations. Therefore, 2-methylbut-2-ene, which forms a tertiary carbocation, is expected to react more quickly with HBr compared to but-2-ene, which forms a secondary carbocation.
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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 (where X is a halogen) to an alkene, the hydrogen atom will attach to the carbon with more hydrogen atoms, and the halogen will attach to the carbon with fewer hydrogen atoms. This rule helps predict the major product of the reaction based on the stability of the carbocation intermediate.
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The 18 and 16 Electron Rule
Carbocation Stability
Carbocation stability is crucial in determining the rate of alkene reactions with HX. Tertiary carbocations are more stable than secondary or primary ones due to hyperconjugation and inductive effects. In the reaction of alkenes with HBr, the formation of a more stable carbocation intermediate leads to a faster reaction rate.
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Steric Hindrance
Steric hindrance refers to the resistance encountered by a chemical reaction due to the size of groups within a molecule. In alkenes, bulky substituents can slow down reactions by impeding the approach of reactants. Comparing but-2-ene and 2-methylbut-2-ene, the latter has more steric hindrance due to the methyl group, potentially affecting its reactivity with HBr.
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Related Practice
Textbook Question
What is the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HCl?
(e)
851
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Textbook Question
In your own words, explain why it is not possible to make primary alkyl halides, such as 1-bromopentane, using the electrophilic addition of HCl or HBr to an alkene.
1001
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Textbook Question
Provide an arrow-pushing mechanism that rationalizes the formation of each of the products you predicted in Assessment 8.31. Make sure your mechanism accounts for all products formed, including stereoisomers and regioisomers, where applicable.
793
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Textbook Question
What is the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HCl?
(d)
1340
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Textbook Question
Provide the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HBr, H2O2
(c)
977
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