Textbook Question
Consider the following compounds that vary from nearly nonacidic to strongly acidic. Draw the conjugate bases of these compounds, and explain why the acidity increases so dramatically with substitution by nitro groups.
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Ch. 2 - Acids and Bases; Functional Groups
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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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 49b
Methyllithium (CH3Li) is often used as a base in organic reactions.
b. What is the conjugate acid of CH3Li? Would you expect CH3Li to be a strong base or a weak base?
Verified step by step guidance1
To determine the conjugate acid of methyllithium (CH3Li), we need to understand the concept of conjugate acids and bases. A conjugate acid is formed when a base gains a proton (H⁺).
Methyllithium (CH3Li) acts as a base by accepting a proton. When CH3Li accepts a proton, it forms CH4 (methane). Therefore, CH4 is the conjugate acid of CH3Li.
To assess whether CH3Li is a strong or weak base, consider the stability of its conjugate acid, CH4. Methane (CH4) is a very stable molecule and does not easily donate a proton, indicating that CH3Li is a strong base.
The strength of a base is often related to the stability of its conjugate acid. Since CH4 is stable and does not readily dissociate to give back a proton, CH3Li is considered a strong base.
In summary, CH3Li is a strong base because its conjugate acid, CH4, is very stable and does not easily release a proton.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Conjugate Acid-Base Pair
In acid-base chemistry, a conjugate acid-base pair consists of two species that transform into each other by the gain or loss of a proton. The conjugate acid of a base is formed when the base accepts a proton. For methyllithium (CH3Li), the conjugate acid is methane (CH4), as CH3Li gains a proton to form CH4.
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Base Pairing Concept 1
Strength of Bases
The strength of a base is determined by its ability to accept protons. Strong bases have a high tendency to accept protons, while weak bases do not. Methyllithium is considered a strong base because it readily accepts protons, forming its conjugate acid, methane, which is a very weak acid, indicating the strong basic nature of CH3Li.
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Acid-Base Equilibrium
Acid-base equilibrium involves the balance between the forward and reverse reactions of acid-base pairs. A strong base like methyllithium shifts the equilibrium towards the formation of its conjugate acid, methane, due to its high proton affinity. Understanding this equilibrium helps predict the behavior of CH3Li in reactions, confirming its role as a strong base.
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Guided course
04:00Determining Acid/Base Equilibrium
Related Practice
Textbook Question
The following compounds can all react as acids.
a. For each compound, show its conjugate base. Show any resonance forms if applicable.
Textbook Question
Label the reactants in these acid–base reactions as Lewis acids (electrophiles) or Lewis bases (nucleophiles). Use curved arrows to show the movement of electron pairs in the reactions.
(b)
Textbook Question
Label the reactants in these acid–base reactions as Lewis acids (electrophiles) or Lewis bases (nucleophiles). Use curved arrows to show the movement of electron pairs in the reactions.
(c)
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Textbook Question
The following compounds can all react as acids.
b. Rank the conjugate bases in the order you would predict, from most stable to least stable.
Textbook Question
Label the reactants in these acid–base reactions as Lewis acids (electrophiles) or Lewis bases (nucleophiles). Use curved arrows to show the movement of electron pairs in the reactions.
(a)