Textbook Question
Propose a mechanism for reaction of the first three propylene units in the polymerization of propylene in the presence of a peroxide.
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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 71
A graduate student attempted to form the iodohydrin of the alkene shown below. Her analysis of the products showed a good yield of an unexpected product. Propose a mechanism to explain the formation of this product.
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Step 1: Analyze the starting material and reaction conditions. The starting material is a cyclic enone with an alcohol group. The reaction conditions involve iodine (I₂) and water (H₂O), which typically facilitate halohydrin formation or electrophilic addition reactions.
Step 2: Consider the electrophilic addition mechanism. Iodine (I₂) can act as an electrophile, reacting with the alkene in the enone to form a cyclic iodonium ion intermediate. This intermediate is highly reactive and can undergo nucleophilic attack.
Step 3: Examine the role of water as a nucleophile. Water can attack the cyclic iodonium ion, leading to the formation of a halohydrin. However, the observed product suggests an alternative pathway involving intramolecular interactions.
Step 4: Propose an intramolecular nucleophilic attack mechanism. The hydroxyl group (-OH) on the starting material can act as a nucleophile, attacking the cyclic iodonium ion. This intramolecular attack leads to the formation of a bicyclic structure with an iodine atom and an ester functional group.
Step 5: Rationalize the stereochemistry of the product. The side view of the product indicates that the iodine atom and the ester group are positioned in a specific stereochemical arrangement. This stereochemistry arises from the constraints of the cyclic structure and the intramolecular attack mechanism.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Iodohydrin Formation
Iodohydrin formation involves the addition of iodine (I2) and water (H2O) across a double bond in an alkene. This reaction typically proceeds through the formation of a cyclic halonium ion intermediate, which is then attacked by water, leading to the formation of an iodohydrin. Understanding this mechanism is crucial for predicting the products formed in the reaction.
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Formation of Enolates
Mechanism of Electrophilic Addition
The mechanism of electrophilic addition describes how alkenes react with electrophiles, such as iodine, to form more stable products. The double bond acts as a nucleophile, attacking the electrophile and forming a carbocation or a cyclic intermediate. This concept is essential for understanding how the unexpected product may arise from the reaction conditions or the structure of the alkene.
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Stereochemistry of Products
Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the case of iodohydrin formation, the stereochemistry of the product can lead to different isomers, including enantiomers or diastereomers. Analyzing the stereochemical outcomes is important for explaining the unexpected product observed in the student's analysis.
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Related Practice
Textbook Question
When styrene (vinylbenzene) is commercially polymerized, about 1–3% of 1,4-divinylbenzene is often added to the styrene. The incorporation of some divinylbenzene gives a polymer with more strength and better resistance to organic solvents. Explain how a very small amount of divinylbenzene has a marked effect on the properties of the polymer.
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Textbook Question
An unknown compound decolorizes bromine in carbon tetrachloride, and it undergoes catalytic reduction to give decalin. When treated with warm, concentrated potassium permanganate, this compound gives cis-cyclohexane-1,2-dicarboxylic acid and oxalic acid. Propose a structure for the unknown compound.
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Textbook Question
The cationic polymerization of isobutylene (2-methylpropene) is shown in Section 8-16A. Isobutylene is often polymerized under free-radical conditions. Propose a mechanism for the free-radical polymerization of isobutylene.
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Textbook Question
The following cyclization has been observed in the oxymercuration-demercuration of this unsaturated alcohol. Propose a mechanism for this reaction.
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Textbook Question
Predict the product of formula C7H13BrO from the reaction of this same unsaturated alcohol with bromine. Propose a mechanism to support your prediction.
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