Textbook Question
Rank the following species in each set from best nucleophile to poorest nucleophile.
c. H2O and NH3 in methanol
d. Br−, Cl−, I− in methanol
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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 77a,b
Bruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 77a,bChapter 10, Problem 77a,b
Draw the substitution products for each of the following reactions; if the products can exist as stereoisomers, show what stereoisomers are obtained:
a. (R)-2-bromopentane+CH3O−
b. (R)-3-bromo-3-methylheptane+CH3OH
Verified step by step guidance1
Step 1: Identify the type of substitution reaction occurring in each case. For (R)-2-bromopentane + CH3O−, the reaction involves a strong nucleophile (CH3O−) and a secondary alkyl halide, which suggests an SN2 mechanism. For (R)-3-bromo-3-methylheptane + CH3OH, the reaction involves a weak nucleophile (CH3OH) and a tertiary alkyl halide, which suggests an SN1 mechanism.
Step 2: For the SN2 reaction (part a), recall that SN2 reactions proceed via a backside attack, leading to inversion of configuration at the stereocenter. Draw the product by replacing the bromine atom with the methoxy group (CH3O−) and invert the stereochemistry from (R) to (S).
Step 3: For the SN1 reaction (part b), recall that SN1 reactions proceed via the formation of a carbocation intermediate. The bromine atom leaves first, forming a tertiary carbocation. Since the carbocation is planar, the nucleophile (CH3OH) can attack from either side, leading to a racemic mixture of stereoisomers (both R and S configurations).
Step 4: Draw the substitution product for part a, ensuring the stereochemistry is inverted due to the SN2 mechanism. For part b, draw both stereoisomers (R and S configurations) resulting from the SN1 mechanism.
Step 5: Verify the stereochemistry of the products and ensure that all substituents are correctly placed. For part a, confirm the inversion of configuration. For part b, confirm the formation of a racemic mixture due to the planar carbocation intermediate.
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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 replaces a leaving group in a molecule. In this context, the nucleophile (CH3O− or CH3OH) attacks the carbon atom bonded to the bromine atom, leading to the formation of a new bond and the release of bromide ion. Understanding the mechanism (either SN1 or SN2) is crucial for predicting the products and their stereochemistry.
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Nucleophiles and Electrophiles can react in Substitution Reactions.
Stereochemistry
Stereochemistry refers to the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the given reactions, the presence of chiral centers means that different stereoisomers can be formed. Recognizing how nucleophilic attacks can lead to different configurations (R/S) is essential for accurately depicting the products and their stereochemical relationships.
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Chirality and Stereoisomers
Chirality is a property of a molecule that makes it non-superimposable on its mirror image, often due to the presence of a chiral center (typically a carbon atom with four different substituents). In the reactions provided, the starting materials are chiral, and the substitution can yield different stereoisomers, including enantiomers and diastereomers. Identifying these stereoisomers is important for understanding the full scope of the reaction products.
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Related Practice
Textbook Question
Draw the substitution products for each of the following reactions; if the products can exist as stereoisomers, show what stereoisomers are obtained:
e. 1-bromo-2-butene + CH3O−
f. 1-bromo-2-butene + CH3OH
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Textbook Question
Draw the substitution products for each of the following reactions; if the products can exist as stereoisomers, show what stereoisomers are obtained:
c. benzyl chloride + CH3CH2OH
d. allyl chloride + CH3OH
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Textbook Question
The pKa of acetic acid in water is 4.76. What effect will a decrease in the polarity of the solvent have on the pKa? Why?
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Textbook Question
Would you expect methoxide ion to be a better nucleophile if it is dissolved in CH3OH or if it is dissolved in DMSO? Why?
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Textbook Question
a. Identify the substitution products that form when 2-bromo-2-methylpropane is dissolved in a mixture of 80% ethanol and 20% water.
b. Explain why the same products are obtained when 2-chloro-2-methylpropane is dissolved in a mixture of 80% ethanol and 20% water.
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