Textbook Question
Which is a stronger acid?
c. <IMAGE>
d. CH3CH2CH2OH or CH3CH2CH2SH
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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 33
Bruice 8th EditionCh. 2 - Acids and Bases: Central to Understanding Organic ChemistryProblem 33Chapter 3, Problem 33
If HCl is a weaker acid than HBr, why is ClCH2COOH a stronger acid than BrCH2COOH?
Verified step by step guidance1
Step 1: Understand the problem. The question is asking why ClCH2COOH (chloroacetic acid) is a stronger acid than BrCH2COOH (bromoacetic acid), despite HCl being a weaker acid than HBr. This involves analyzing the inductive effect of the halogen substituents (Cl and Br) on the carboxylic acid group.
Step 2: Recall the concept of electronegativity. Chlorine (Cl) is more electronegative than bromine (Br). Electronegativity is the ability of an atom to attract electrons towards itself. This property plays a key role in the inductive effect.
Step 3: Explain the inductive effect. The electronegative halogen substituent (Cl or Br) pulls electron density away from the carboxylic acid group through the sigma bonds. This stabilizes the negative charge on the conjugate base (CH2COO⁻) after the acid donates a proton (H⁺). A more stable conjugate base corresponds to a stronger acid.
Step 4: Compare the inductive effects of Cl and Br. Since Cl is more electronegative than Br, it exerts a stronger inductive effect. This means ClCH2COOH has a more stabilized conjugate base compared to BrCH2COOH, making it a stronger acid.
Step 5: Summarize the reasoning. The strength of ClCH2COOH as an acid is due to the stronger inductive effect of chlorine compared to bromine, which stabilizes the conjugate base more effectively. This explains why ClCH2COOH is a stronger acid than BrCH2COOH, even though HCl is a weaker acid than HBr.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid Strength and Electronegativity
Acid strength is influenced by the stability of the conjugate base formed after deprotonation. In this case, the electronegativity of the halogen atoms plays a crucial role. Chlorine is more electronegative than bromine, which means that the negative charge on the conjugate base (ClCH2COO-) is better stabilized by the chlorine atom compared to the bromine atom in BrCH2COO-. This stabilization leads to ClCH2COOH being a stronger acid.
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1:47
Electronegativity
Inductive Effect
The inductive effect refers to the electron-withdrawing or electron-donating effects that substituents have on a molecule. In ClCH2COOH, the chlorine atom exerts a strong electron-withdrawing inductive effect, which stabilizes the negative charge on the conjugate base. In contrast, bromine, being larger and less electronegative, exerts a weaker inductive effect, resulting in less stabilization of the conjugate base BrCH2COO-, making BrCH2COOH a weaker acid.
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01:47Understanding the Inductive Effect.
Comparative Acid-Base Strength
When comparing acids, it is essential to consider both the strength of the acid and the stability of its conjugate base. Although HCl is a weaker acid than HBr, the specific structural context of ClCH2COOH and BrCH2COOH alters their acid strengths. The combination of electronegativity and inductive effects in the respective carboxylic acids leads to ClCH2COOH being a stronger acid than BrCH2COOH despite the general trend observed with HCl and HBr.
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02:49The Lewis definition of acids and bases.
Related Practice
Textbook Question
Fosamax (shown on the previous page) has six acidic groups. The active form of the drug, which has lost two of its acidic protons, is shown in the box.
(Notice that the phosphorus atom in Fosamax and the sulfur atom in [Problem 36] can be surrounded by more than eight electrons because P and S are below the second row of the periodic table.)
a. Why are the OH groups bonded to phosphorus the strongest acids of the six groups?
b. Which of the remaining four groups is the weakest acid?
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Textbook Question
For each of the following compounds, indicate the atom that is protonated when an acid is added to a solution of the compound.
a.
b.
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Textbook Question
For each of the following compounds, indicate the atom that is protonated when an acid is added to a solution of the compound.
c.
d.
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1
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Textbook Question
Which is a stronger acid?
c. CH3OCH2CH2CH2OHorCH3CH2OCH2CH2OH
d.
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Textbook Question
Which is a stronger base?
a.
b.
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