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 62b
Bruice 8th EditionCh. 2 - Acids and Bases: Central to Understanding Organic ChemistryProblem 62bChapter 3, Problem 62b
Explain the relative acidities.
CH2═CHCH2OH, CH3CH2CH2OH, HC≡CCH2OH
Verified step by step guidance1
Step 1: Begin by understanding the concept of acidity. Acidity is determined by the ability of a compound to donate a proton (H⁺). The more stable the conjugate base after losing a proton, the stronger the acid.
Step 2: Analyze the structure of each compound and identify the functional groups. CH2═CHCH2OH contains an alcohol group (-OH) attached to an allylic carbon, CH3CH2CH2OH contains an alcohol group attached to a saturated alkyl chain, and HC≡CCH2OH contains an alcohol group attached to a propargylic carbon (next to a triple bond).
Step 3: Consider the effects of resonance and electronegativity. In CH2═CHCH2OH, the allylic position allows for resonance stabilization of the conjugate base, making it more acidic. In HC≡CCH2OH, the triple bond increases the electronegativity of the adjacent carbon, stabilizing the conjugate base and increasing acidity. CH3CH2CH2OH lacks resonance or significant electronegativity effects, making it the least acidic.
Step 4: Evaluate the inductive effects. Electronegative groups or bonds near the -OH group can pull electron density away, stabilizing the conjugate base. The triple bond in HC≡CCH2OH exerts a stronger inductive effect compared to the double bond in CH2═CHCH2OH, further increasing its acidity.
Step 5: Rank the compounds based on their relative acidities. HC≡CCH2OH is the most acidic due to the strong inductive effect and stabilization of the conjugate base. CH2═CHCH2OH is moderately acidic due to resonance stabilization. CH3CH2CH2OH is the least acidic as it lacks resonance or significant inductive effects.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acidity and pKa
Acidity refers to the tendency of a compound to donate a proton (H+) in solution. The strength of an acid is often measured by its pKa value, where lower pKa values indicate stronger acids. Understanding the pKa helps predict the relative acidities of different compounds, as it reflects the stability of the conjugate base formed after deprotonation.
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Identifying pKa values
Inductive Effect
The inductive effect describes how the presence of electronegative atoms or groups can influence the acidity of a molecule by stabilizing or destabilizing the conjugate base. Electron-withdrawing groups increase acidity by stabilizing the negative charge on the conjugate base, while electron-donating groups decrease acidity by destabilizing it.
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01:47Understanding the Inductive Effect.
Hybridization and Acidity
The hybridization of the atom bearing the acidic proton significantly affects acidity. For example, sp-hybridized carbons (like in alkynes) hold their electrons closer to the nucleus, resulting in stronger acids compared to sp2 (alkenes) or sp3 (alkanes) hybridized carbons. This is due to the increased s-character in sp hybridization, which stabilizes the negative charge on the conjugate base.
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Related Practice
Textbook Question
A single bond between two carbons with different hybridizations has a small dipole. What is the direction of the dipole in the indicated bonds?
a.
b.
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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
Given the Ka values, estimate the pKa value of each of the following acids without using a calculator (that is, is it between 3 and 4, between 9 and 10, and so on?):
1. nitrous acid (HNO2), Ka = 4.0 × 10−4
2. nitric acid (HNO3), Ka = 22
3. bicarbonate (HCO3−), Ka = 6.3 × 10−11
4. hydrogen cyanide (HCN), Ka = 7.9 × 10−10
5. formic acid (HCOOH), Ka = 2.0 × 10−4
6. phosphoric acid (H3PO4), Ka = 2.1
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Textbook Question
For each compound, indicate the atom that is most apt to be protonated.
a.
b.
c.
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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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