Textbook Question
What are the major 1,2- and 1,4-addition products of the following reaction? Indicate the kinetic and the thermodynamic products.
a.
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Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
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Bruice 8th EditionCh. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of BenzeneProblem 32b
Bruice 8th EditionCh. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of BenzeneProblem 32bChapter 9, Problem 32b
What are the products of the following reactions, assuming that one equivalent of each reagent is used in each reaction? Disregard stereoisomers.
b. 
Verified step by step guidance1
Step 1: Analyze the structure of the starting compound. The molecule contains two double bonds, which are conjugated (alternating single and double bonds). This conjugation stabilizes the molecule and affects the reactivity of the double bonds.
Step 2: Recognize the reagent used in the reaction. HBr (hydrobromic acid) is a strong acid that adds across double bonds in an electrophilic addition reaction. Since only one equivalent of HBr is used, it will react with one of the double bonds.
Step 3: Determine the regioselectivity of the reaction. The addition of HBr follows Markovnikov's rule, where the hydrogen atom adds to the carbon of the double bond that already has more hydrogen atoms, and the bromine atom adds to the carbon with fewer hydrogen atoms.
Step 4: Identify the most reactive double bond. In conjugated systems, the double bond closer to the alkyl substituent (more substituted) is typically more reactive due to stabilization of the carbocation intermediate formed during the reaction.
Step 5: Predict the product. The HBr will add across the more reactive double bond, resulting in the formation of a brominated alkene. The remaining double bond will stay intact, and stereoisomers are disregarded as per the problem statement.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electrophilic Addition Reactions
Electrophilic addition reactions involve the addition of an electrophile to a nucleophile, typically across a double bond. In this case, HBr acts as the electrophile, where the hydrogen atom adds to one carbon of the double bond and the bromine adds to the other. Understanding this mechanism is crucial for predicting the products formed in the reaction.
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Features of Addition Mechanisms.
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 the greater number of hydrogen atoms already attached, while the halide (Br in this case) will attach to the carbon with fewer hydrogen atoms. This rule helps in determining the regioselectivity of the product formed during the reaction.
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1,2 vs 1,4 Addition
In conjugated systems, electrophilic addition can occur at different positions, leading to 1,2 or 1,4 addition products. The 1,2 addition occurs when the electrophile adds to adjacent carbons, while 1,4 addition involves the electrophile adding to carbons that are separated by one carbon. Recognizing these pathways is essential for predicting the major products in reactions involving conjugated systems.
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Related Practice
Textbook Question
Which of the double bonds in zingiberene, the compound responsible for the aroma of ginger, is most reactive in an electrophilic addition reaction with HBr?
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Textbook Question
What are the major 1,2- and 1,4-addition products of the following reaction? Indicate the kinetic and the thermodynamic products.
b.
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Textbook Question
What are the products of the following reactions, assuming that one equivalent of each reagent is used in each reaction? Disregard stereoisomers.
a.
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Textbook Question
What products would be obtained from the reaction of 1,3,5-hexatriene with one equivalent of HBr? Disregard stereoisomers.
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Textbook Question
A student wanted to know whether the greater proximity of the nucleophile to the C-2 carbon in the transition state is what causes the 1,2-addition product to be formed faster when 1,3-butadiene reacts with HCl. Therefore, she decided to investigate the reaction of 2-methyl-1,3-cyclohexadiene with HCl. Her friend told her that she should use 1-methyl-1,3-cyclohexadiene instead. Should she follow her friend's advice?
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