Textbook Question
Under certain conditions, the reaction of 0.5 M 1-bromobutane with 1.0 M sodium methoxide forms 1-methoxybutane at a rate of 0.05 mol/L per second. What would be the rate if 0.1 M 1-bromobutane and 2.0 M NaOCH3 were used?
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Ch.6 - Alkyl Halides; Nucleophilic Substitution
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 6, Problem 14a
Predict the major products of the following substitutions.
a. 
Verified step by step guidance1
Identify the type of reaction: Potassium tert-butoxide ((CH3)3CO⁻ K⁺) is a strong, bulky base. This suggests that the reaction will likely proceed via an E2 elimination mechanism rather than a substitution, as bulky bases favor elimination over substitution.
Analyze the substrate: Ethyl bromide (CH3CH2Br) is a primary alkyl halide. Primary alkyl halides typically undergo elimination with strong, bulky bases like tert-butoxide.
Determine the elimination product: In an E2 elimination, the base abstracts a proton (H⁺) from the β-carbon (the carbon adjacent to the carbon bonded to the leaving group, Br⁻). The electrons from the C-H bond form a double bond between the α-carbon (the carbon bonded to the leaving group) and the β-carbon, while the leaving group (Br⁻) departs.
Draw the product: The elimination of HBr from ethyl bromide results in the formation of ethene (CH2=CH2) as the major product. This is because ethene is the simplest alkene that can form from this reaction.
Verify the reaction conditions: Confirm that the reaction conditions (strong, bulky base and primary alkyl halide) are consistent with the E2 mechanism and that no competing SN2 reaction occurs due to steric hindrance from the bulky base.
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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 a molecule by a nucleophile. In this context, potassium tert-butoxide acts as a strong nucleophile that can attack the electrophilic carbon in ethyl bromide, leading to the formation of a new bond and the release of bromide ion as a leaving group.
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Nucleophiles and Electrophiles can react in Substitution Reactions.
Sterics and Nucleophilicity
Sterics refers to the spatial arrangement of atoms in a molecule and can significantly influence reaction pathways. Potassium tert-butoxide is a bulky nucleophile, which favors elimination reactions over substitution due to steric hindrance. Understanding how sterics affects nucleophilicity is crucial for predicting the major products in this reaction.
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08:27Nucleophilic Addition
E2 Elimination Mechanism
The E2 elimination mechanism is a concerted reaction where a base removes a proton from a β-carbon while the leaving group departs from the α-carbon, resulting in the formation of a double bond. In the presence of a strong base like potassium tert-butoxide, the reaction with ethyl bromide is likely to proceed via E2, leading to the formation of an alkene as the major product.
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09:36Drawing the E2 Mechanism.
Related Practice
Textbook Question
Predict the major products of the following substitutions.
b.
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Textbook Question
Predict the major products of the following substitutions.
e. 1-chloropentane + NaI →
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Textbook Question
Predict the major products of the following substitutions.
d. CH3CH2CH2I + NaCN →
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Textbook Question
Under certain conditions, the reaction of 0.5 M 1-bromobutane with 1.0 M sodium methoxide forms 1-methoxybutane at a rate of 0.05 mol/L per second.
c. Show another SN2 reaction using a different combination of an alkoxide and an alkyl bromide that also produces 1-methoxybutane.
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Textbook Question
Consider the reaction of 1-bromobutane with a large excess of ammonia (NH3). Draw the reactants, the transition state, and the products. Note that the initial product is the salt of an amine (RNH3+Br−), which is deprotonated by the excess ammonia to give the amine.
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