Textbook Question
Does methanol behave as an acid or a base when it reacts with methylamine?
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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 13
Bruice 8th EditionCh. 2 - Acids and Bases: Central to Understanding Organic ChemistryProblem 13Chapter 3, Problem 13
a. Which is a stronger base: CH3COO− or HCOO−? (The pKa of CH3COOH is 4.8; the pKa of HCOOH is 3.8.)
b. Which is a stronger base: HO− or -NH2? (The pKa of H2O is 15.7; the pKa of NH3 is 36.)
c. Which is a stronger base: H2O or CH3OH? (The pKa of H3O+ is −1.7; the pKa of CH3O+H2 is −2.5.)
Verified step by step guidance1
Step 1: Understand the relationship between pKa and base strength. The strength of a base is inversely related to the strength of its conjugate acid. A lower pKa value of the conjugate acid indicates a stronger acid, and thus, a weaker conjugate base. Conversely, a higher pKa value of the conjugate acid indicates a weaker acid, and thus, a stronger conjugate base.
Step 2: For part (a), compare CH3COO− and HCOO−. The conjugate acids are CH3COOH (pKa = 4.8) and HCOOH (pKa = 3.8), respectively. Since CH3COOH has a higher pKa than HCOOH, it is a weaker acid. Therefore, CH3COO− is the stronger base compared to HCOO−.
Step 3: For part (b), compare HO− and -NH2. The conjugate acids are H2O (pKa = 15.7) and NH3 (pKa = 36), respectively. Since NH3 has a much higher pKa than H2O, it is a much weaker acid. Therefore, -NH2 is a significantly stronger base compared to HO−.
Step 4: For part (c), compare H2O and CH3OH. The conjugate acids are H3O+ (pKa = −1.7) and CH3O+H2 (pKa = −2.5), respectively. Since H3O+ has a higher pKa than CH3O+H2, it is a weaker acid. Therefore, H2O is the stronger base compared to CH3OH.
Step 5: Summarize the results: (a) CH3COO− is the stronger base, (b) -NH2 is the stronger base, and (c) H2O is the stronger base. This conclusion is based on the pKa values of the conjugate acids and the inverse relationship between acid strength and base strength.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Strength and pKa
The strength of an acid or base is often measured by its pKa value, which indicates the tendency of an acid to donate protons. A lower pKa value corresponds to a stronger acid, meaning it dissociates more readily in solution. Conversely, the strength of a base can be inferred from the pKa of its conjugate acid; a higher pKa of the conjugate acid indicates a stronger base.
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07:45
Identifying pKa values
Conjugate Acid-Base Pairs
In acid-base chemistry, every acid has a corresponding conjugate base, and vice versa. The relationship between an acid and its conjugate base is crucial for determining relative strengths. For example, if an acid has a low pKa, its conjugate base will be a stronger base. Understanding these pairs helps in comparing the basicity of different species.
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Comparative Basicity
To determine which of two bases is stronger, one can compare the pKa values of their conjugate acids. The base that corresponds to the acid with the higher pKa is the stronger base. This comparative approach is essential in evaluating the basicity of different species, as seen in the examples provided in the question.
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Related Practice
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
Draw the conjugate acid of each of the following:
a. CH3CH2OH
b. CH3CH2O−
c.
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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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4. <IMAGE>
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Textbook Question
Antacids are compounds that neutralize stomach acid. Write the equations that show how Milk of Magnesia, Alka-Seltzer, and Tums remove excess acid.
a. Milk of Magnesia: Mg(OH)2
b. Alka-Seltzer: KHCO3 and NaHCO3
c. Tums: CaCO3
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Textbook Question
Estimate the pKa values of the following compounds:
c. CH3CH2COOH
d. CH3CH2CH2N+H3
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