Textbook Question
Rank the compounds in each set in order of increasing acid strength.
(a) CH3CH2COOH, CH3CHBrCOOH, CH3CBr2COOH
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Ch. 20 - Carboxylic Acids
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 20, Problem 3b
Rank the compounds in each set in order of increasing acid strength.
(b) CH3CH2CH2CHBrCOOH, CH3CH2CHBrCH2COOH, CH3CHBrCH2CH2COOH
Verified step by step guidance1
Step 1: Understand the concept of acid strength. Acid strength is influenced by the stability of the conjugate base formed after the acid donates a proton. Electron-withdrawing groups, such as halogens, stabilize the conjugate base by delocalizing the negative charge, increasing acid strength.
Step 2: Analyze the compounds provided. Each compound contains a carboxylic acid group (-COOH) and a bromine atom (-Br) attached to different positions in the carbon chain. The position of the bromine atom relative to the carboxylic acid group affects the acid strength due to the inductive effect.
Step 3: Evaluate the inductive effect. The closer the bromine atom is to the carboxylic acid group, the stronger the electron-withdrawing effect, which stabilizes the conjugate base and increases acid strength.
Step 4: Rank the compounds based on the position of the bromine atom. For CH3CH2CH2CHBrCOOH, the bromine is furthest from the carboxylic acid group, resulting in the weakest acid. For CH3CH2CHBrCH2COOH, the bromine is closer, making it a stronger acid. For CH3CHBrCH2CH2COOH, the bromine is closest to the carboxylic acid group, resulting in the strongest acid.
Step 5: Final ranking in order of increasing acid strength: CH3CH2CH2CHBrCOOH < CH3CH2CHBrCH2COOH < CH3CHBrCH2CH2COOH.
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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 ability of a compound to donate a proton (H+) in solution. The strength of an acid is often quantified by its pKa value; lower pKa values indicate stronger acids. Understanding the relationship between structure and acidity is crucial, as factors such as electronegativity and resonance can significantly influence a compound's ability to stabilize the negative charge of its conjugate base.
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07:45
Identifying pKa values
Inductive Effect
The inductive effect describes the electron-withdrawing or electron-donating influence of substituents on a molecule. Electronegative atoms, such as halogens, can stabilize the negative charge of a conjugate base through their electron-withdrawing properties, thereby increasing acidity. In the context of the given compounds, the position and number of halogen substituents will affect their relative acid strengths.
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01:47Understanding the Inductive Effect.
Resonance Stabilization
Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. This delocalization can stabilize the conjugate base formed after deprotonation, enhancing acidity. In the compounds provided, the presence of resonance structures can significantly influence their acid strengths, particularly when combined with inductive effects from substituents.
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03:43The radical stability trend.
Related Practice
Textbook Question
Suppose you have just synthesized heptanoic acid from heptan-1-ol. The product is contaminated by sodium dichromate, sulfuric acid, heptan-1-ol, and possibly heptanal. Explain how you would use acid–base extractions to purify the heptanoic acid. Use a chart, like that in Figure 20-3, to show where the impurities are at each stage.
Textbook Question
Phenols are less acidic than carboxylic acids, with values of pKa around 10. Phenols are deprotonated by (and therefore soluble in) solutions of sodium hydroxide but not by solutions of sodium bicarbonate. Explain how you would use extractions to isolate the three pure compounds from a mixture of p-cresol (p-methylphenol), cyclohexanone, and benzoic acid.
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Textbook Question
Rank the compounds in each set in order of increasing acid strength.
(c)
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Textbook Question
Name the following carboxylic acids (when possible, give both a common name and a systematic name).
(a)
(b)
(c)
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Textbook Question
Name the following carboxylic acids (when possible, give both a common name and a systematic name).
(d)
(e)
(f)