Ch. 21 - Conjugated Systems I: Stability and Addition Reactions

Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition

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Ch. 21 - Conjugated Systems I: Stability and Addition Reactions

Problem 43a

Chapter 20, Problem 43a

Predict the product of the following reactions.
(a)

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Identify the reaction type: The reaction involves a diketone and an α,β-unsaturated ketone in the presence of a base (NaOH) and heat, suggesting a Michael addition followed by an intramolecular aldol condensation.

Michael addition: The enolate ion formed from the diketone will attack the β-carbon of the α,β-unsaturated ketone, resulting in a 1,4-addition. This step forms a new carbon-carbon bond.

Intramolecular aldol condensation: The newly formed compound will undergo an intramolecular aldol reaction. The enolate ion generated from the remaining ketone group will attack the carbonyl carbon of the other ketone group, forming a cyclic β-hydroxy ketone.

Dehydration: The β-hydroxy ketone will undergo dehydration (loss of water) to form an α,β-unsaturated ketone, resulting in a conjugated cyclic product.

Consider stereochemistry: Analyze the stereochemistry of the final product, as the formation of new chiral centers during the reaction may lead to stereoisomers.

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Key Concepts

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

Reaction Mechanisms

Understanding reaction mechanisms is crucial in organic chemistry as they describe the step-by-step process by which reactants transform into products. This includes identifying intermediates, transition states, and the movement of electrons. Familiarity with mechanisms helps predict the outcome of reactions and the stability of products formed.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Recognizing functional groups allows chemists to predict reactivity and the types of reactions that can occur. For example, alcohols, carboxylic acids, and amines each have distinct behaviors in chemical reactions.

Stereochemistry

Stereochemistry involves the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. It is essential for predicting the products of reactions, especially in cases where chirality or geometric isomerism is involved. Understanding stereochemistry helps in determining the specific isomers that may be formed during a reaction.

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Related Practice

Textbook Question

Predict the product of the following reactions.

(a)

1230

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Textbook Question

Predict the product of the following reactions.

(b)

585

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Textbook Question

Would you expect the following nucleophiles to do 1,2- or 1,4-addition?

(g)

(h)

(i)

1101

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Textbook Question

Whereas stabilized enolates do 1,4-addition, unstabilized (normal) enolates can do both 1,2- and 1,4-addition depending on the situation. Why might this be?

789

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Textbook Question

Show how the following molecule might be synthesized using the Robinson annulation.

703

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Textbook Question

Would you expect the following nucleophiles to do 1,2- or 1,4-addition?

(d)

(e)

(f)

711