Textbook Question
Which is a better nucleophile?
c. CH3O− or CH3OH in H2O
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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 12e,f
Bruice 8th EditionCh. 9 - Substitution and Elimination Reactions of Alkyl HalidesProblem 12e,fChapter 10, Problem 12e,f
Which is a better nucleophile?
e. HO− or -NH2 in NH3
f. HO− or -NH2 in DMSO
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 nucleophiles in question. Both HO⁻ (hydroxide ion) and NH₂⁻ (amide ion) are negatively charged, which generally makes them strong nucleophiles. However, their relative nucleophilicity depends on the solvent and their intrinsic properties.
Step 3: Consider the solvent in part (e), which is NH₃ (ammonia). NH₃ is a polar protic solvent, meaning it can form hydrogen bonds with nucleophiles. Polar protic solvents stabilize smaller, more electronegative nucleophiles like HO⁻ through hydrogen bonding, reducing their nucleophilicity. NH₂⁻, being less electronegative and larger, is less stabilized by hydrogen bonding and thus remains a stronger nucleophile in NH₃.
Step 4: Consider the solvent in part (f), which is DMSO (dimethyl sulfoxide). DMSO is a polar aprotic solvent, meaning it does not form hydrogen bonds with nucleophiles. In polar aprotic solvents, nucleophilicity is less affected by solvent stabilization, and the intrinsic properties of the nucleophiles dominate. NH₂⁻ is still a better nucleophile than HO⁻ because nitrogen is less electronegative than oxygen, making NH₂⁻ more willing to donate its lone pair of electrons.
Step 5: Summarize the findings. In NH₃ (polar protic solvent), NH₂⁻ is a better nucleophile than HO⁻ because it is less stabilized by hydrogen bonding. In DMSO (polar aprotic solvent), NH₂⁻ is also a better nucleophile than HO⁻ due to its lower electronegativity and greater intrinsic nucleophilicity.
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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. Stronger nucleophiles are typically negatively charged or have lone pairs that can be readily donated. Understanding nucleophilicity is essential for predicting reaction mechanisms in organic chemistry.
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Solvent Effects
The solvent can significantly influence nucleophilicity by stabilizing or destabilizing the nucleophile. Protic solvents, like ammonia (NH3), can solvate nucleophiles through hydrogen bonding, often reducing their reactivity. In contrast, aprotic solvents, such as dimethyl sulfoxide (DMSO), do not solvate anions as effectively, allowing nucleophiles to remain more reactive. Recognizing the role of solvents is crucial for evaluating nucleophilic strength in different environments.
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Comparative Nucleophilicity
When comparing nucleophiles, factors such as charge and steric hindrance must be considered. For example, hydroxide (HO−) is generally a stronger nucleophile than amide (−NH2) in protic solvents due to its negative charge. However, in aprotic solvents, the relative nucleophilicity can change based on the solvent's ability to stabilize the nucleophiles. Analyzing these comparisons helps in predicting which nucleophile will be more effective in a given reaction.
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Related Practice
Textbook Question
a. Which is a stronger base: RO− or RS−?
b. Which is a better nucleophile in an aqueous solution?
c. Which is a better nucleophile in DMSO?
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Textbook Question
Which substitution reaction takes place more rapidly?
a. CH3CH2Br + H2O or CH3CH2Br + HO−
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Textbook Question
Which substitution reaction takes place more rapidly?
c.
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Textbook Question
Which substitution reaction takes place more rapidly?
b.
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Textbook Question
Which is a better nucleophile?
d. CH3O− or CH3OH in DMSO
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