Textbook Question
Rank the following species in order of increasing acidity. Explain your reasons for ordering them as you do.
HF NH3 H2SO4 CH3OH CH3COOH H3O+ H2O
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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 36a
All of the following compounds can react as acids. Without using a table of acidities, rank them in order of increasing acidity. Explain your ranking.
a. CH3CH2SO3H
b. CH3CH2OH
c. CH3CH2COOH
d. CH3CHClCOOH
e. ClCH2CH2COOH
Verified step by step guidance1
Identify the functional groups present in each compound. For example, CH3CH2SO3H contains a sulfonic acid group, CH3CH2OH contains an alcohol group, CH3CH2COOH contains a carboxylic acid group, CH3CHClCOOH contains a carboxylic acid group with a chlorine substituent, and ClCH2CH2COOH contains a carboxylic acid group with a chlorine substituent.
Understand the general acidity trend: sulfonic acids are typically stronger acids than carboxylic acids, which are stronger than alcohols. This is due to the stability of the conjugate base formed after deprotonation.
Consider the effect of electronegative substituents on acidity. Chlorine is an electronegative atom that can stabilize the conjugate base through inductive effects, increasing the acidity of the compound.
Compare the compounds with chlorine substituents: CH3CHClCOOH and ClCH2CH2COOH. The position of the chlorine atom relative to the acidic proton affects the inductive effect. Closer proximity generally results in greater stabilization of the conjugate base and increased acidity.
Rank the compounds based on the analysis: CH3CH2SO3H is likely the most acidic due to the sulfonic acid group, followed by the carboxylic acids with chlorine substituents (considering the position of chlorine), then CH3CH2COOH, and finally CH3CH2OH as the least acidic due to the alcohol group.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid Strength and Structure
Acid strength is influenced by the stability of the conjugate base formed after deprotonation. Factors such as electronegativity, resonance, and inductive effects play a crucial role in stabilizing the conjugate base, thereby increasing the acidity of the compound. Understanding these structural influences helps in predicting and ranking the acidity of different compounds.
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03:09
The 3 factors that determine the strength of inductive effects.
Inductive Effect
The inductive effect refers to the electron-withdrawing or electron-donating influence exerted by atoms or groups through sigma bonds. Electronegative atoms, like chlorine, can stabilize the conjugate base by pulling electron density away, enhancing acidity. This effect is crucial in comparing compounds with similar functional groups but different substituents.
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01:47Understanding the Inductive Effect.
Resonance Stabilization
Resonance stabilization occurs when the conjugate base can delocalize its negative charge over multiple atoms, increasing stability. Carboxylic acids, for example, benefit from resonance between the oxygen atoms, making them generally more acidic than alcohols. Recognizing resonance patterns is essential for assessing the relative acidity of organic compounds.
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03:43The radical stability trend.
Related Practice
Textbook Question
The Ka of phenylacetic acid is 5.2 × 10−5, and the pKa of propionic acid is 4.87.
a. Calculate the pKa of phenylacetic acid and the Ka of propionic acid.
b. Which of these is the stronger acid? Calculate how much stronger an acid it is.
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Textbook Question
The Ka of phenylacetic acid is 5.2 × 10−5, and the pKa of propionic acid is 4.87.
c. Predict whether the following equilibrium will favor the reactants or the products.
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Textbook Question
Predict which compound in each pair has the higher boiling point. Explain your prediction.
(e)
(f)
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Textbook Question
Rank the following species in order of increasing basicity. Explain your reasons for ordering them as you do.
NH3 CH3O– H2O CH3COO– NaOH NH2– HSO4–
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Textbook Question
Predict which compound in each pair has the higher boiling point. Explain your prediction.
(c) CH3CH2CH2CH2CH3 or (CH3)2CH2CH2CH3
(d) CH3CH2CH2CH2CH3 or CH3CH2CH2CH2CH2Cl
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