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 13b
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.
Verified step by step guidance1
Step 1: Identify the type of reaction. This is a nucleophilic substitution reaction (SN2 mechanism) where ammonia (NH3) acts as the nucleophile and 1-bromobutane (CH3CH2CH2CH2Br) is the substrate. The bromine atom is the leaving group.
Step 2: Draw the reactants. Represent 1-bromobutane as CH3CH2CH2CH2Br and ammonia as NH3. Show the lone pair of electrons on the nitrogen atom in NH3, which will attack the carbon atom bonded to the bromine.
Step 3: Illustrate the transition state. In the SN2 mechanism, the nucleophile (NH3) attacks the electrophilic carbon atom from the opposite side of the leaving group (Br−). Draw a pentavalent carbon in the transition state with partial bonds to both the nucleophile (NH3) and the leaving group (Br−). Use dashed lines to represent these partial bonds.
Step 4: Draw the initial product. After the bromine leaves, the nitrogen from NH3 is bonded to the carbon chain, forming CH3CH2CH2CH2NH3+. This is the ammonium salt (RNH3+ Br−), where R = CH3CH2CH2CH2.
Step 5: Show the deprotonation step. The excess ammonia (NH3) acts as a base and removes a proton (H+) from CH3CH2CH2CH2NH3+, resulting in the formation of the neutral amine (CH3CH2CH2CH2NH2) and ammonium bromide (NH4+ Br−).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nucleophilic Substitution
Nucleophilic substitution is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophile, resulting in the replacement of a leaving group. In the case of 1-bromobutane reacting with ammonia, the ammonia acts as a nucleophile, attacking the carbon atom bonded to the bromine, leading to the formation of an amine.
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Transition State
The transition state is a high-energy, unstable arrangement of atoms that occurs during a chemical reaction. It represents the point at which reactants are transformed into products. In this reaction, the transition state would involve the partial bond formation between the nitrogen of ammonia and the carbon of 1-bromobutane, as well as the partial bond breaking of the C-Br bond.
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Deprotonation
Deprotonation is the removal of a proton (H+) from a molecule, resulting in the formation of a base. In this reaction, after the initial product (RNH3+ Br−) is formed, the excess ammonia deprotonates the ammonium salt to yield the neutral amine. This step is crucial for obtaining the final product and illustrates the role of ammonia as both a nucleophile and a base.
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Related Practice
Textbook Question
Classify each reaction as a substitution, an elimination, or neither. Identify the leaving group in each reaction, and the nucleophile in substitutions.
c.
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Textbook Question
Classify each reaction as a substitution, an elimination, or neither. Identify the leaving group in each reaction, and the nucleophile in substitutions.
b.
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Textbook Question
Predict the major products of the following substitutions.
b.
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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
Predict the major products of the following substitutions.
a.
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