Textbook Question
Keto–enol tautomerism is a reaction we discuss in detail in Chapter 19. Estimate the equilibrium constant of this reaction (BDE for C―C π bond = 65 kcal/mol ; for C―O π bond = 85 kcal/mol).
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Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics
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
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Mullins 1st EditionCh. 5 - Chemical Reaction Analysis: Thermodynamics and KineticsProblem 57b
Mullins 1st EditionCh. 5 - Chemical Reaction Analysis: Thermodynamics and KineticsProblem 57bChapter 4, Problem 57b
(b) Mechanistically, the reaction occurs as shown below. Why is this reaction favored? Based on the stability of the anions, estimate Keq.
Verified step by step guidance1
Step 1: Analyze the reaction mechanism provided in the problem. Identify the reactants, intermediates, and products, and determine the type of reaction (e.g., substitution, elimination, addition).
Step 2: Consider the stability of the anions involved in the reaction. Anion stability is influenced by factors such as resonance, inductive effects, hybridization, and electronegativity. Compare the stability of the anions on both sides of the reaction.
Step 3: Recall that the equilibrium constant (K_eq) is related to the relative stability of the products and reactants. A reaction is favored when the products are more stable than the reactants. Use the stability of the anions to qualitatively estimate whether K_eq is greater than, less than, or approximately equal to 1.
Step 4: Write the expression for K_eq in terms of the concentrations of the products and reactants. For example, \( K_{eq} = \frac{[\text{Products}]}{[\text{Reactants}]} \). Use the stability analysis to predict the direction of the equilibrium.
Step 5: Conclude why the reaction is favored based on the stability of the anions and the estimated value of K_eq. Highlight the role of thermodynamic stability in driving the reaction forward.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Reaction Mechanism
A reaction mechanism describes the step-by-step sequence of elementary reactions by which overall chemical change occurs. Understanding the mechanism helps in predicting the products and the rate of the reaction. It often involves identifying intermediates and transition states, which are crucial for analyzing how the reaction proceeds and why certain pathways are favored.
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Stability of Anions
The stability of anions is a key factor in determining the favorability of a reaction. Anions are negatively charged species, and their stability can be influenced by factors such as electronegativity, resonance, and inductive effects. More stable anions are generally formed in reactions that are thermodynamically favorable, leading to a lower energy transition state and a higher equilibrium constant (K_eq).
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Equilibrium Constant (K_eq)
The equilibrium constant (K_eq) quantifies the ratio of the concentrations of products to reactants at equilibrium for a reversible reaction. A larger K_eq indicates that the products are favored at equilibrium, while a smaller K_eq suggests that reactants are favored. Estimating K_eq based on the stability of anions involves considering how the formation of more stable anions shifts the equilibrium position towards the products.
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02:19The relationship between equilibrium constant and pKa.
Related Practice
Textbook Question
Reaction (c), on the other hand, is favored (∆G° < 0). Identify the bonds formed and broken and explain this result in light of (a) and (b).
(c)
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Textbook Question
Calculate ∆H° for the following alkene addition reaction, one we discuss further in Chapter 7. Predict the sign of ∆S° . (The BDE for C―C π bond is approximately 65 kcal/mol.)
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Textbook Question
Draw a reaction coordinate diagram, making sure to label reactants (R), products (P), intermediates (I), transition states (‡), activation energies ( Ea) , and ∆G°, for each of the following.
(c) a slightly endothermic, three-step reaction where the first step is rate-determining
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Textbook Question
Draw a reaction coordinate diagram, making sure to label reactants (R), products (P), intermediates (I), transition states (‡), activation energies ( Ea) , and ∆G°, for each of the following.
(d) a slightly exothermic, three-step reaction where the third step is rate-determining.
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Textbook Question
Reactions (a) and (b) are disfavored overall (∆G° > 0), yet they are favored based on ∆H°. Identify the bonds formed and broken for (a) and (b).
(b)
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