Textbook Question
Consider the type of orbitals involved, and rank the following nitrogen compounds in order of decreasing basicity. 2. Rank the conjugate acids in order of increasing acidity. (Hint: These two orders should be the same!)
Ch. 2 - Acids and Bases; Functional Groups
Wade9th EditionOrganic ChemistryISBN: 9780135213728
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 2, Problem 18
Which is a stronger base: ethoxide ion or acetate ion? Give pKb values (without looking them up) to support your choice.
Verified step by step guidance1
Identify the conjugate acids of the given bases: Ethoxide ion (C₂H₅O⁻) is the conjugate base of ethanol (C₂H₅OH), and acetate ion (CH₃COO⁻) is the conjugate base of acetic acid (CH₃COOH).
Recall that the strength of a base is inversely related to the strength of its conjugate acid. A weaker conjugate acid corresponds to a stronger base.
Consider the acidity of the conjugate acids: Ethanol is a weaker acid compared to acetic acid. This is because ethanol lacks the resonance stabilization that acetic acid has, which makes acetic acid a stronger acid.
Since ethanol is a weaker acid, its conjugate base, the ethoxide ion, is a stronger base compared to the acetate ion.
Estimate the pKb values: Since ethoxide ion is a stronger base, it will have a lower pKb value compared to the acetate ion. The exact pKb values are not needed, but this reasoning supports the conclusion that ethoxide ion is the stronger base.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Strength
The strength of a base is determined by its ability to accept protons. A stronger base has a higher tendency to accept protons, which is often reflected in its pKb value. The lower the pKb, the stronger the base. Understanding this concept helps compare the basicity of ethoxide and acetate ions.
Recommended video:
2:50
Acid-Base Catalysis Concept 3
Resonance Stabilization
Resonance stabilization occurs when a molecule can delocalize electrons across multiple atoms, reducing its reactivity. Acetate ion is resonance-stabilized, making it less reactive and a weaker base compared to ethoxide ion, which lacks such stabilization. This concept is crucial for understanding why ethoxide is a stronger base.
Recommended video:
Guided course
03:43The radical stability trend.
Inductive Effect
The inductive effect involves the transmission of charge through a chain of atoms in a molecule, affecting its acidity or basicity. In ethoxide ion, the electron-donating effect of the ethyl group increases electron density on the oxygen, enhancing its basicity. This concept helps explain the relative strength of ethoxide as a base compared to acetate.
Recommended video:
Guided course
01:47Understanding the Inductive Effect.
Related Practice
Textbook Question
Acetic acid can also react as a very weak base (pKb = 20). Two different sites on acetic acid might become protonated to give the conjugate acid. Draw both of these possible conjugate acids, and explain (resonance) why the correct one is more stable. Calculate the pKa of this conjugate acid.
1
views
Textbook Question
Consider each pair of bases, and explain which one is more basic. Draw their conjugate acids, and show which one is a stronger acid.
(a)
(b)
1
views
Textbook Question
Give the structures of their conjugate acids, and estimate their pKas from similar compounds in Appendix 4.
Textbook Question
Choose the more acidic member of each pair of isomers, and show why the acid you chose is more acidic.
(d)
(e)
8
views
Textbook Question
Choose the more acidic member of each pair of isomers, and show why the acid you chose is more acidic.
(a)
(b)
(c)
1
views