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Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
Chapter 22, Problem 68f

Show how you would use an aldol, Claisen, or another type of condensation to make each compound.
(f) Chemical structures illustrating a Claisen condensation reaction, featuring two carbonyl compounds and a benzene ring.

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Step 1: Identify the target molecule. The compound shown is a β-diketone with two ketone groups separated by a single carbon atom. This structure suggests it can be synthesized using a Claisen condensation reaction, which is commonly used to form β-diketones.
Step 2: Choose appropriate starting materials. For a Claisen condensation, you need an ester and a ketone or two esters. In this case, the starting materials could be cyclohexanone (a ketone) and benzyl acetate (an ester containing the benzene ring).
Step 3: Set up the reaction conditions. A Claisen condensation requires a strong base, such as sodium ethoxide (NaOEt), to deprotonate the α-hydrogen of the ketone or ester, making it nucleophilic. The reaction is typically carried out in an alcohol solvent, such as ethanol.
Step 4: Mechanism of the reaction. The base deprotonates the α-hydrogen of cyclohexanone, forming an enolate ion. This enolate then attacks the carbonyl carbon of benzyl acetate, leading to the formation of a β-diketone after subsequent protonation and elimination of the leaving group (ethoxide).
Step 5: Purify the product. After the reaction is complete, the β-diketone product can be isolated and purified using techniques such as recrystallization or column chromatography to obtain the desired compound.

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Key Concepts

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

Aldol Condensation

Aldol condensation is a reaction between aldehydes or ketones that contain alpha-hydrogens, leading to the formation of β-hydroxy aldehydes or ketones. This reaction involves the nucleophilic addition of an enolate ion to a carbonyl compound, followed by dehydration to yield an α,β-unsaturated carbonyl compound. Understanding this mechanism is crucial for synthesizing complex organic molecules.
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Claisen Condensation

Claisen condensation is a reaction between two esters or an ester and a carbonyl compound in the presence of a strong base, resulting in the formation of a β-keto ester or a β-diketone. This reaction involves the formation of an enolate ion from one ester, which then attacks the carbonyl carbon of the other ester. Mastery of this reaction is essential for constructing carbon skeletons in organic synthesis.
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Condensation Reactions

Condensation reactions are a class of reactions where two molecules combine to form a larger molecule, typically with the loss of a small molecule such as water. These reactions are fundamental in organic chemistry for building complex structures and can involve various functional groups. Recognizing the conditions and mechanisms of different condensation reactions is vital for effective synthetic strategies.
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