Textbook Question
Rank the following alcohols from strongest to weakest acid.
CH2═CHCH2OH; CH3CH2CH2OH; HC≡CCH2OH
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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 60c
Bruice 8th EditionCh. 2 - Acids and Bases: Central to Understanding Organic ChemistryProblem 60cChapter 3, Problem 60c
For each of the following compounds, draw the form that predominates at pH = 3, pH = 6, pH = 10, and pH = 14:
c. CF3CH2OH (pKa = 12.4)
Verified step by step guidance1
Step 1: Understand the relationship between pH and pKa. The pKa of a compound is the pH at which half of the compound exists in its protonated form and half in its deprotonated form. When pH < pKa, the protonated form predominates. When pH > pKa, the deprotonated form predominates.
Step 2: Identify the functional group in CF3CH2OH. The compound contains an alcohol (-OH) group, which can lose a proton to form an alkoxide ion (-O⁻). The pKa of the alcohol group is given as 12.4.
Step 3: Analyze the compound at pH=3. Since pH=3 is much lower than the pKa (12.4), the protonated form (CF3CH2OH) will predominate because the environment is highly acidic.
Step 4: Analyze the compound at pH=6 and pH=10. Both pH values are still below the pKa (12.4), so the protonated form (CF3CH2OH) will continue to predominate, though at pH=10, a small fraction of the compound may start to deprotonate.
Step 5: Analyze the compound at pH=14. Since pH=14 is much higher than the pKa (12.4), the deprotonated form (CF3CH2O⁻) will predominate because the environment is highly basic.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Chemistry
Acid-base chemistry involves the study of proton transfer reactions, where acids donate protons (H+) and bases accept them. The pH scale measures the acidity or basicity of a solution, with lower values indicating higher acidity. Understanding how compounds behave as acids or bases at different pH levels is crucial for predicting their predominant forms in solution.
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The Lewis definition of acids and bases.
pKa and its Significance
The pKa value is a quantitative measure of the strength of an acid in solution, representing the pH at which half of the acid is dissociated. A lower pKa indicates a stronger acid. In this context, the pKa of 12.4 for CF3CH2OH suggests that at pH values below this, the compound will predominantly exist in its protonated form, while at higher pH values, it will be deprotonated.
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Protonation and Deprotonation
Protonation refers to the addition of a proton to a molecule, while deprotonation is the removal of a proton. The predominant form of a compound at a given pH depends on its pKa relative to the pH. For CF3CH2OH, at pH 3 and 6, it will be mostly protonated, while at pH 10 and 14, it will be predominantly deprotonated, reflecting its behavior as a weak acid.
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Related Practice
Textbook Question
Rank the following compounds from strongest to weakest acid:
CH3CH2OH; CH3CH2NH2; CH3CH2SH; CH3CH2CH3
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Textbook Question
Give the products of the following acid–base reactions and indicate whether reactants or products are favored at equilibrium.
b. CH3CH2OH + -NH2 ⇌
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Textbook Question
For each of the following compounds, draw the form that predominates at pH = 3, pH = 6, pH = 10, and pH = 14:
a. CH3COOH (pKa = 4.8)
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Textbook Question
For each of the following compounds, draw the form that predominates at pH = 3, pH = 6, pH = 10, and pH = 14:
b. CH3CH2N+H3 (pKa = 11.0)
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Textbook Question
Give the products of the following acid–base reactions and indicate whether reactants or products are favored at equilibrium.
a.
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