Textbook Question
Rank the ions (−CH3, −NH2, HO−, and F−) from most basic to least basic.
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Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry
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. 2 - Acids and Bases: Central to Understanding Organic ChemistryProblem 18a
Bruice 8th EditionCh. 2 - Acids and Bases: Central to Understanding Organic ChemistryProblem 18aChapter 3, Problem 18a
Which of the following bases can remove a proton from acetic acid in a reaction that favors products?
HO− CH3NH2 HC≡C− CH3OH H2O Cl−
Verified step by step guidance1
Step 1: Understand the problem. The question asks which base can remove a proton from acetic acid in a reaction that favors products. This involves comparing the acidity of acetic acid and the conjugate acids of the given bases to determine if the reaction is thermodynamically favorable.
Step 2: Recall the concept of acid-base reactions. A base can remove a proton from an acid if the conjugate acid of the base is weaker (less acidic) than the original acid. This is determined by comparing the pKa values of acetic acid and the conjugate acids of the bases provided.
Step 3: Analyze acetic acid. Acetic acid (CH3COOH) has a pKa of approximately 4.76. Any base whose conjugate acid has a pKa higher than 4.76 can favorably remove a proton from acetic acid.
Step 4: Evaluate each base and its conjugate acid:
- HO⁻ (hydroxide ion): Its conjugate acid is H2O (water), which has a pKa of 15.7.
- CH3NH2 (methylamine): Its conjugate acid is CH3NH3⁺, with a pKa of approximately 10.6.
- HC≡C⁻ (acetylide ion): Its conjugate acid is HC≡CH (acetylene), with a pKa of approximately 25.
- CH3OH (methanol): Its conjugate acid is CH3OH2⁺, with a pKa of approximately -2.2.
- H2O (water): Its conjugate acid is H3O⁺ (hydronium ion), with a pKa of -1.7.
- Cl⁻ (chloride ion): Its conjugate acid is HCl (hydrochloric acid), with a pKa of -7.
Step 5: Compare pKa values. Bases whose conjugate acids have pKa values higher than 4.76 can remove a proton from acetic acid in a reaction that favors products. Based on the pKa values, HO⁻, CH3NH2, and HC≡C⁻ are strong enough bases to deprotonate acetic acid, while CH3OH, H2O, and Cl⁻ are not.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acidity and Basicity
Acidity refers to the tendency of a compound to donate protons (H+ ions), while basicity is the ability of a compound to accept protons. In the context of acetic acid (CH3COOH), its acidity is determined by the stability of the acetate ion (CH3COO−) formed after deprotonation. Understanding the relative strengths of acids and bases is crucial for predicting the direction of the reaction.
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06:21
Understanding the difference between basicity and nucleophilicity.
pKa Values
The pKa value is a quantitative measure of the strength of an acid in solution; it indicates the acidity of a compound. Lower pKa values correspond to stronger acids, which more readily donate protons. For acetic acid, the pKa is approximately 4.76, meaning that bases with a pKa higher than this value can effectively deprotonate acetic acid, favoring the formation of products.
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07:45Identifying pKa values
Reaction Equilibrium
In chemical reactions, equilibrium refers to the state where the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. The position of equilibrium can be influenced by the strength of the acids and bases involved. A reaction that favors products will have a stronger base that can effectively remove a proton from the acid, shifting the equilibrium towards the products.
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04:00Determining Acid/Base Equilibrium
Related Practice
Textbook Question
Ethyne (HC≡CH) has a pKa value of 25, water has a pKa value of 15.7, and ammonia (NH3) has a pKa value of 36. Draw the equation, showing equilibrium arrows that indicate whether reactants or products are favored, for the acid–base reaction of ethyne with
b. −NH2.
c. Which would be a better base to use if you wanted to remove a proton from ethyne, HO− or -NH2?
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Textbook Question
Rank the carbanions shown in the margin from most basic to least basic.
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Textbook Question
For each of the acid–base reactions in [Section 2.3], compare the pKa values of the acids on either side of the equilibrium arrows to prove that the equilibrium lies in the direction indicated.
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Textbook Question
Ethyne (HC≡CH) has a pKa value of 25, water has a pKa value of 15.7, and ammonia (NH3) has a pKa value of 36. Draw the equation, showing equilibrium arrows that indicate whether reactants or products are favored, for the acid–base reaction of ethyne with
a. HO-.
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Textbook Question
Calculate the equilibrium constant for the acid–base reaction between the reactants in each of the following pairs:
c. CH3NH2 + H2O
d. CH3N+H3 + H2O
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