Textbook Question
Predict the major product(s) for each reaction. Include stereochemistry where appropriate.
c. cis-but-2-ene + Cl2/H2O
d. trans-but-2-ene + Cl2/H2O
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Ch.8 - Reactions of Alkenes
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 8, Problem 22a
Show how you would accomplish the following synthetic conversions.
a. 3-methylpent-2-ene → 2-chloro-3-methylpentan-3-ol
Problem-Solving Hint: The opening of a halonium ion is driven by its electrophilic nature. The weak nucleophile attacks the carbon bearing more positive charge.
Verified step by step guidance1
Step 1: Begin by recognizing that the starting material, 3-methylpent-2-ene, is an alkene. Alkenes are reactive toward electrophilic addition reactions, which will be key in this transformation.
Step 2: Perform a halogenation reaction using Cl₂ in the presence of a polar solvent like CH₂Cl₂. This will generate a chloronium ion intermediate. The halonium ion forms because the alkene reacts with Cl₂, and one chlorine atom attaches to one of the double-bonded carbons while the other forms the halonium ion bridge.
Step 3: Identify the site of nucleophilic attack. The halonium ion is electrophilic, and the nucleophile (water, H₂O) will attack the more substituted carbon of the halonium ion due to its greater positive charge. This leads to the formation of a chlorohydrin intermediate, where a hydroxyl group (-OH) is added to the more substituted carbon and a chlorine atom remains attached to the less substituted carbon.
Step 4: Consider the stereochemistry of the product. The attack of the nucleophile (water) occurs anti to the halonium ion bridge, resulting in anti-addition of the hydroxyl and chlorine groups.
Step 5: Verify the final product structure. The resulting compound is 2-chloro-3-methylpentan-3-ol, where the hydroxyl group is attached to the tertiary carbon (C3) and the chlorine atom is attached to the secondary carbon (C2).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Halonium Ion Mechanism
A halonium ion is a cyclic intermediate formed during the electrophilic addition of halogens to alkenes. This intermediate is characterized by a three-membered ring structure where a halogen atom is positively charged and bonded to two carbon atoms. The electrophilic nature of the halonium ion makes it susceptible to nucleophilic attack, typically at the more substituted carbon, leading to the formation of more stable products.
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Nucleophilic Attack
Nucleophilic attack refers to the process where a nucleophile, which is an electron-rich species, donates a pair of electrons to an electrophile, forming a new bond. In the context of the halonium ion, a weak nucleophile attacks the carbon atom that bears a greater positive charge, which is often the more substituted carbon due to the stability of the resulting carbocation. This step is crucial for the conversion of alkenes to more complex organic molecules.
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Stereochemistry in Organic Reactions
Stereochemistry involves the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In synthetic conversions, the stereochemical outcome can influence the properties of the final product, such as its reactivity and biological activity. Understanding stereochemistry is essential when predicting the configuration of products formed during reactions, especially when dealing with chiral centers.
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Related Practice
Textbook Question
Give the expected major product for each reaction, including stereochemistry where applicable.
(a) but-1-ene + H2/Pt
(b) cis-but-2-ene + H2/Ni
1338
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Textbook Question
Predict the major product(s) for each reaction. Include stereochemistry where appropriate.
e. 1-methylcyclopentene + Br2 in saturated aqueous NaCl
1091
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Textbook Question
Show how you would accomplish the following synthetic conversions.
b. chlorocyclohexane → trans-2-chlorocyclohexanol
Problem-Solving Hint: The opening of a halonium ion is driven by its electrophilic nature. The weak nucleophile attacks the carbon bearing more positive charge.
1135
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Textbook Question
Show how you would accomplish the following synthetic conversions.
c. 1-methylcyclopentanol → 2-chloro-1-methylcyclopentanol
Problem-Solving Hint: The opening of a halonium ion is driven by its electrophilic nature. The weak nucleophile attacks the carbon bearing more positive charge.
950
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Textbook Question
Predict the major product(s) for each reaction. Include stereochemistry where appropriate.
a. 1-methylcyclohexene + Cl2/H2O
b. 2-methylbut-2-ene + Br2/H2O
2009
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