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Ch. 17 - Reactions at the Alpha-Carbon
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBruice 8th EditionCh. 17 - Reactions at the Alpha-CarbonProblema 65a
Capitolo 17, Problema 65a

There are other condensation reactions similar to the aldol and Claisen condensations:
a. The Perkin condensation is the condensation of an aromatic aldehyde and acetic anhydride. Draw the product obtained from the following Perkin condensation:
Chemical reaction diagram illustrating the Perkin condensation between an aromatic aldehyde and acetic anhydride.

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Identify the reactants in the Perkin condensation: an aromatic aldehyde (e.g., benzaldehyde) and acetic anhydride. The reaction typically occurs in the presence of a base, such as sodium acetate, which facilitates the reaction.
Understand the mechanism: The base deprotonates the methyl group of acetic anhydride, forming an enolate ion. This enolate ion acts as a nucleophile in the reaction.
The enolate ion attacks the carbonyl carbon of the aromatic aldehyde, forming a β-hydroxy intermediate. This step is analogous to the aldol addition step in aldol condensation.
The β-hydroxy intermediate undergoes dehydration (loss of water) to form an α,β-unsaturated carbonyl compound. This step is driven by the formation of a conjugated system, which is thermodynamically stable.
Draw the final product: The product will be an α,β-unsaturated carbonyl compound where the aromatic ring is conjugated with the double bond and the carbonyl group. Ensure the structure reflects the correct connectivity and stereochemistry, if applicable.

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Perkin Condensation

The Perkin condensation is a reaction that involves the condensation of an aromatic aldehyde with an anhydride, typically acetic anhydride, in the presence of a base. This reaction results in the formation of α,β-unsaturated carboxylic acids. Understanding this reaction is crucial for predicting the structure of the product formed from the specific reactants provided in the question.
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Condensation Reactions

Aromatic Aldehydes

Aromatic aldehydes are organic compounds that contain a carbonyl group (C=O) bonded to a carbon atom of an aromatic ring. They play a significant role in various organic reactions, including the Perkin condensation. Recognizing the structure and reactivity of aromatic aldehydes is essential for determining the outcome of the condensation reaction.
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Name the aldehyde

Acetic Anhydride

Acetic anhydride is a reactive acylating agent commonly used in organic synthesis, particularly in condensation reactions. It can donate an acetyl group (CH3CO-) to other molecules, facilitating the formation of new carbon-carbon bonds. Familiarity with acetic anhydride's properties and its role in the Perkin condensation is vital for understanding the mechanism and predicting the product.
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Anhydride Nomenclature
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There are other condensation reactions similar to the aldol and Claisen condensations:

c. The Knoevenagel condensation is the condensation of an aldehyde or a ketone that has no a-hydrogens and a compound such as diethyl malonate that has an a-carbon flanked by two electron-withdrawing groups. Draw the product obtained from the following Knoevenagel condensation:

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There are other condensation reactions similar to the aldol and Claisen condensations:

b. What compound is formed if water is added to the product of a Perkin condensation?

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Domanda del libro di testo

A β-ɣ-unsaturated carbonyl compound rearranges to a more stable conjugated ⍺,β-unsaturated compound in the presence of either acid or base. b. Propose a mechanism for the acid-catalyzed rearrangement.

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Show how 4-methyl-3-hexanol can be synthesized from 3-pentanone.

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Show how the following compound can be synthesized from the given starting material. (Hint: Start with an acetoacetic ester.)

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What product is obtained when the product of a Knoevenagel condensation is heated in an aqueous acidic solution?

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