Textbook Question
What nucleophiles would form the following compounds as a result of reacting with 1-iodobutane?
g.
1
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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 71a,b
Bruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 71a,bChapter 10, Problem 71a,b
Explain how each of the following changes affect the rate of the reaction of 1-bromobutane with ethoxide ion in DMF.
a. The concentration of both the alkyl halide and the nucleophile are tripled.
b. The solvent is changed to ethanol.
Verified step by step guidance1
The reaction of 1-bromobutane with ethoxide ion in DMF is an example of an SN2 reaction. In an SN2 reaction, the rate is determined by the rate law: \( \text{Rate} = k[\text{1-bromobutane}][\text{ethoxide ion}] \). This means the reaction is second-order overall, depending on the concentrations of both the alkyl halide and the nucleophile.
a. If the concentration of both the alkyl halide (1-bromobutane) and the nucleophile (ethoxide ion) are tripled, substitute the new concentrations into the rate law. The new rate will be \( \text{Rate}_{\text{new}} = k(3[\text{1-bromobutane}])(3[\text{ethoxide ion}]) \). Simplify this to \( \text{Rate}_{\text{new}} = 9k[\text{1-bromobutane}][\text{ethoxide ion}] \). This shows that the rate of the reaction will increase by a factor of 9.
b. Changing the solvent to ethanol affects the reaction because ethanol is a protic solvent, whereas DMF is an aprotic solvent. In an SN2 reaction, aprotic solvents like DMF stabilize the nucleophile less, allowing it to remain more reactive. Protic solvents like ethanol, on the other hand, can hydrogen bond with the nucleophile, reducing its reactivity. This means the rate of the reaction will decrease when the solvent is changed to ethanol.
To summarize, the rate of the reaction is directly proportional to the concentrations of both the alkyl halide and the nucleophile, and the solvent choice significantly impacts the nucleophile's reactivity in an SN2 mechanism.
For part (a), the rate increases by a factor of 9 when concentrations are tripled. For part (b), the rate decreases when the solvent is changed to ethanol due to reduced nucleophilicity in a protic solvent.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nucleophilic Substitution Reactions
Nucleophilic substitution reactions involve the replacement of a leaving group in an organic molecule by a nucleophile. In the case of 1-bromobutane reacting with ethoxide ion, the reaction mechanism can be either SN1 or SN2, depending on factors like steric hindrance and solvent. Understanding the mechanism is crucial for predicting how changes in concentration and solvent will affect the reaction rate.
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Nucleophiles and Electrophiles can react in Substitution Reactions.
Reaction Rate and Concentration
The rate of a chemical reaction is influenced by the concentrations of the reactants. For a bimolecular reaction like the SN2 mechanism, tripling the concentration of both the alkyl halide and the nucleophile will increase the reaction rate significantly, as the rate is directly proportional to the product of the concentrations of the two reactants. This relationship is described by the rate law for the reaction.
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Effect of Solvent on Reaction Mechanism
The choice of solvent can greatly influence the rate and mechanism of a nucleophilic substitution reaction. DMF (dimethylformamide) is a polar aprotic solvent that stabilizes ions and enhances nucleophilicity, favoring SN2 reactions. In contrast, ethanol is a polar protic solvent that can solvate nucleophiles and reduce their reactivity, potentially favoring an SN1 mechanism and slowing the reaction rate.
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Related Practice
Textbook Question
What nucleophiles would form the following compounds as a result of reacting with 1-iodobutane?
h.
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Textbook Question
What nucleophiles would form the following compounds as a result of reacting with 1-iodobutane?
e.
f.
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Textbook Question
Explain how each of the following changes affect the rate of the reaction of 1-bromobutane with ethoxide ion in DMF.
c. The alkyl halide is changed to 1-chlorobutane.
d. The alkyl halide is changed to 2-bromobutane.
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Textbook Question
Explain how the following changes affect the rate of the reaction of 2-bromo-2-methylbutane with methanol:
a. The alkyl halide is changed to 2-chloro-2-methylbutane.
b. The alkyl halide is changed to 2-chloro-3-methylbutane.
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Textbook Question
Starting with cyclohexene, how can the following compounds be prepared?
a. methoxycyclohexane
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