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Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 5 - Chemical Reaction Analysis: Thermodynamics and KineticsProblem 63c
Chapter 4, Problem 63c

Parts (a)–(d) of this assessment assist in the development of what will become a common theme in organic reactions and should be worked in order. [Think carefully about how each question relates to the others.]
(c) Without worrying about the mechanism of the reaction, estimate an equilibrium constant for the following carbonyl addition reaction based on the relative stability of the Lewis bases.
Diagram illustrating a carbonyl addition reaction with arrows indicating electron movement between reactants.

Verified step by step guidance
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Analyze the reaction: The image shows a nucleophilic addition reaction where a methyl anion (CH₃⁻) attacks the carbonyl carbon of acetone (propanone), resulting in the formation of a tetrahedral intermediate with a negatively charged oxygen atom.
Consider the relative stability of the Lewis bases: The methyl anion (CH₃⁻) is a strong nucleophile but less stable due to its negative charge on a carbon atom. The negatively charged oxygen in the product is more stable because oxygen is more electronegative and better accommodates the negative charge.
Relate stability to equilibrium: The equilibrium constant (K_eq) for the reaction depends on the relative stability of the reactants and products. Since the negatively charged oxygen in the product is more stable than the methyl anion in the reactants, the equilibrium will favor the product side.
Estimate the equilibrium constant qualitatively: A reaction that favors the formation of a more stable product typically has a K_eq greater than 1. Thus, the equilibrium constant for this reaction is expected to be greater than 1, indicating that the product is favored.
Conclude the reasoning: The equilibrium constant estimation is based on the principle that reactions tend to favor the side with more stable species. Here, the stability of the negatively charged oxygen in the product drives the equilibrium toward the product side.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Equilibrium Constant (K)

The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction. It provides insight into the position of equilibrium, indicating whether products or reactants are favored. A larger K value suggests that products are favored, while a smaller K indicates a preference for reactants.
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The relationship between equilibrium constant and pKa.

Lewis Acids and Bases

Lewis acids and bases are defined by their ability to accept or donate electron pairs, respectively. In the context of carbonyl addition reactions, the stability of the Lewis bases involved can significantly influence the reaction's equilibrium. A more stable Lewis base will favor the formation of products, thereby affecting the equilibrium constant.
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The Lewis definition of acids and bases.

Carbonyl Addition Reactions

Carbonyl addition reactions involve the nucleophilic attack of a Lewis base on the electrophilic carbon of a carbonyl group (C=O). This type of reaction is fundamental in organic chemistry, leading to the formation of alcohols or other functional groups. Understanding the stability of the reactants and products is crucial for estimating the equilibrium constant in these reactions.
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Addition Reactions of Furan Concept 1
Related Practice
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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Textbook Question

In light of your answers to parts (b) and (c), where both were shown to be quite favorable, imagine a scenario where either reaction is possible. Of the two, which would you expect to be faster? Which would you expect to be more favored? Explain each in the context of the important thermodynamic and/or kinetic parameters.

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Textbook Question

The hydrogenation of alkenes is a reaction we study in Chapter 9.

(b) Is this reaction favored or disfavored in terms of entropy?

Textbook Question

In Chapter 13, we discuss the ring-opening reactions of epoxides, such as the one shown here.

(b) Predict the sign of ∆S°.

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Textbook Question

Calculate Keq for the following acid–base reaction.

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Textbook Question

In Chapter 13, we discuss the ring-opening reactions of epoxides, such as the one shown here.

(a) Based on the bonds formed and the bonds broken, calculate ∆H°.

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