Textbook Question
For each indicated proton, suggest an approximate pKa value from Table 4.5. Rationalize your choice.
(b)
1
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Ch. 4 - Acids and Bases: Electron Flow
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
Chapter 3, Problem 38d
Calculate Keq for these acid–base reactions.
(d) 
Verified step by step guidance1
Step 1: Identify the acid and base on both sides of the reaction. In this case, the alcohol (CH3CH2OH) acts as the acid, and hydroxide ion (OH⁻) acts as the base. On the product side, the ethoxide ion (CH3CH2O⁻) is the conjugate base, and water (H2O) is the conjugate acid.
Step 2: Determine the pKa values of the acid and conjugate acid. The pKa of ethanol (CH3CH2OH) is approximately 16, and the pKa of water (H2O) is approximately 15.7.
Step 3: Use the relationship between pKa values and equilibrium constant (Keq). The formula is: Keq = 10^(pKa(conjugate acid) - pKa(acid)).
Step 4: Substitute the pKa values into the formula. Here, pKa(conjugate acid) = 15.7 (for H2O) and pKa(acid) = 16 (for CH3CH2OH).
Step 5: Calculate the exponent (pKa difference) and express the equilibrium constant (Keq) in terms of 10 raised to the power of the difference. This will give the final Keq value for the reaction.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Equilibrium Constant (K_eq)
The equilibrium constant, K_eq, quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction. It is calculated using the formula K_eq = [products]/[reactants], where the concentrations are raised to the power of their coefficients in the balanced equation. A K_eq greater than 1 indicates that products are favored, while a value less than 1 suggests that reactants are favored.
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02:19
The relationship between equilibrium constant and pKa.
Acid-Base Reactions
Acid-base reactions involve the transfer of protons (H+) between reactants. In these reactions, acids donate protons, while bases accept them. Understanding the strength of acids and bases, often represented by their dissociation constants (K_a for acids and K_b for bases), is crucial for predicting the direction of the reaction and calculating K_eq.
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02:49The Lewis definition of acids and bases.
Le Chatelier's Principle
Le Chatelier's Principle states that if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance and restore a new equilibrium. This principle is essential in predicting how changes in concentration, pressure, or temperature will affect the position of equilibrium in acid-base reactions, thereby influencing the calculation of K_eq.
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Related Practice
Textbook Question
For each indicated proton, suggest an approximate pKa value from Table 4.5. Rationalize your choice.
(d)
2
views
Textbook Question
Using qualitative reasoning for the acid–base reactions shown,
(i) which is stronger, the base or the conjugate base?
(ii) Which side of the reaction is favored?
(iii) Would you expect a Keq greater than or less than 1?
(a)
1
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Textbook Question
Using qualitative reasoning for the acid–base reactions shown,
(i) which is stronger, the base or the conjugate base?
(ii) Which side of the reaction is favored?
(iii) Would you expect a Keq greater than or less than 1?
(c)
1
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Textbook Question
For the bases shown, draw the conjugate acid and identify a pKa value from Table 4.5 that would help you accurately estimate its stability.
(b)
1
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Textbook Question
Calculate Keq for these acid–base reactions.
(c)
2
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