Textbook Question
Rank the following species in each set from best nucleophile to poorest nucleophile.
b.
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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 74c,d
Bruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 74c,dChapter 10, Problem 74c,d
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
Verified step by step guidance1
Step 1: Understand the concept of nucleophilicity. Nucleophilicity refers to the ability of a species to donate a pair of electrons to an electrophile. It is influenced by factors such as charge, electronegativity, solvent effects, and steric hindrance.
Step 2: Analyze the solvent. Methanol is a polar protic solvent, meaning it can form hydrogen bonds with nucleophiles. Polar protic solvents tend to stabilize smaller, more electronegative nucleophiles through hydrogen bonding, reducing their nucleophilicity. Larger, less electronegative nucleophiles are less stabilized and thus more nucleophilic in such solvents.
Step 3: Compare H₂O and NH₃ in methanol. NH₃ (ammonia) is less electronegative than H₂O (water), meaning it holds its lone pair of electrons less tightly and is more willing to donate them. Additionally, NH₃ is less hydrogen-bonded in methanol compared to H₂O, making NH₃ the better nucleophile in this solvent.
Step 4: Compare Br⁻, Cl⁻, and I⁻ in methanol. In polar protic solvents like methanol, larger anions are better nucleophiles because they are less solvated (less stabilized by hydrogen bonding). I⁻ is the largest ion, followed by Br⁻, and then Cl⁻. Therefore, the nucleophilicity order in methanol is I⁻ > Br⁻ > Cl⁻.
Step 5: Summarize the rankings. For part (c), NH₃ is a better nucleophile than H₂O in methanol. For part (d), the nucleophilicity order in methanol is I⁻ > Br⁻ > Cl⁻. These rankings are based on the effects of the polar protic solvent and the intrinsic properties of the nucleophiles.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nucleophilicity
Nucleophilicity refers to the ability of a species to donate an electron pair to an electrophile, forming a chemical bond. It is influenced by factors such as charge, electronegativity, and solvent effects. Generally, negatively charged species are stronger nucleophiles than their neutral counterparts, and nucleophilicity can vary significantly in different solvents.
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Solvent Effects
The solvent can significantly impact nucleophilicity by stabilizing or destabilizing the nucleophile. In polar protic solvents like methanol, nucleophiles are often less nucleophilic due to solvation effects, where solvent molecules surround and stabilize the nucleophile, making it less available to react. Understanding how solvents interact with nucleophiles is crucial for predicting their reactivity.
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Comparative Nucleophilicity of Halides
When comparing halide ions (Br−, Cl−, I−), their nucleophilicity generally increases down the group in the periodic table due to decreasing electronegativity and increasing size. Iodide (I−) is typically the strongest nucleophile among the three, while bromide (Br−) is stronger than chloride (Cl−). This trend is important for ranking nucleophiles in reactions.
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Related Practice
Textbook Question
Rank the following species in each set from best nucleophile to poorest nucleophile.
a.
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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:
a. (R)-2-bromopentane+CH3O−
b. (R)-3-bromo-3-methylheptane+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
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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Textbook Question
Starting with cyclohexene, how can the following compounds be prepared?
c. dicyclohexyl ether
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