Textbook Question
The reaction of chloromethane with hydroxide ion at 30 °C has a ΔG° value of −21.7 kcal/mol. What is the equilibrium constant for the reaction?
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Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides
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. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 130
Bruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 130Chapter 10, Problem 130
Explain why the following alkyl halide does not undergo a substitution reaction, regardless of the base that is used.
Verified step by step guidance1
Analyze the structure of the alkyl halide provided in the image. The molecule contains a bromine atom attached to a highly sterically hindered carbon center, which is part of a bicyclic system.
Understand the mechanism of substitution reactions. Substitution reactions, such as SN1 and SN2, require either the formation of a carbocation intermediate (SN1) or direct attack by a nucleophile (SN2). Both mechanisms are affected by steric hindrance and the stability of intermediates.
For an SN1 reaction, the bromine would need to leave, forming a carbocation. However, the carbon attached to bromine is part of a rigid bicyclic structure, making carbocation formation highly unstable due to strain and steric hindrance. This prevents the SN1 pathway.
For an SN2 reaction, the nucleophile would need to directly attack the carbon bonded to bromine. The bulky bicyclic structure creates significant steric hindrance, blocking the nucleophile from accessing the carbon atom. This prevents the SN2 pathway.
Conclude that the combination of steric hindrance and the instability of potential intermediates makes this alkyl halide unreactive in substitution reactions, regardless of the base or nucleophile used.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Steric Hindrance
Steric hindrance refers to the prevention of chemical reactions due to the spatial arrangement of atoms within a molecule. In bulky alkyl halides, such as the one shown, the presence of large groups around the reactive site can obstruct the approach of nucleophiles, making substitution reactions less favorable or impossible.
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02:53
Understanding steric effects.
Substitution Mechanisms (SN1 and SN2)
Substitution reactions can occur via two primary mechanisms: SN1 and SN2. SN1 reactions involve a two-step process where the leaving group departs first, forming a carbocation, while SN2 reactions involve a single concerted step where the nucleophile attacks the substrate as the leaving group departs. The structure of the alkyl halide influences which mechanism is favored; in this case, steric hindrance may prevent both mechanisms from occurring.
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03:32How do we predict if the mechanism is SN1 or SN2?
Carbocation Stability
Carbocation stability is crucial in determining the feasibility of substitution reactions. Tertiary carbocations are more stable than secondary or primary ones due to hyperconjugation and inductive effects from surrounding alkyl groups. If the alkyl halide cannot form a stable carbocation due to steric hindrance, it will not undergo substitution, regardless of the base used.
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05:58Determining Carbocation Stability
Related Practice
Textbook Question
When equivalent amounts of methyl bromide and sodium iodide are dissolved in methanol, the concentration of iodide ion quickly decreases and then slowly returns to its original concentration. Account for this observation.
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Textbook Question
For each of the following compounds, draw the product that forms in an E2 reaction and indicate its configuration:
a. (1S,2S)-1-bromo-1,2-diphenylpropane
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Textbook Question
For each of the following compounds, draw the product that forms in an E2 reaction and indicate its configuration:
b. (1S,2R)-1-bromo-1,2-diphenylpropane
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