Predict the products of the following aldol condensations. Show the products both before and after dehydration.
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Verified step by step guidance

1. Step 1: Identify the reactants and the type of reaction. The reactants are benzaldehyde (PhCHO) and acetone (CH3COCH3), and the reaction is an aldol condensation under basic conditions (-OH). Aldol condensation involves the formation of a β-hydroxy ketone or aldehyde followed by dehydration to form an α,β-unsaturated carbonyl compound.
2. Step 2: Determine the enolate formation. Under basic conditions, acetone will form an enolate ion by deprotonation of one of its α-hydrogens. The enolate ion is nucleophilic and will attack the electrophilic carbonyl carbon of benzaldehyde.
3. Step 3: Perform the nucleophilic addition. The enolate ion from acetone attacks the carbonyl carbon of benzaldehyde, forming a β-hydroxy ketone intermediate. This intermediate contains both a hydroxyl group (-OH) and a ketone group (-C=O) on adjacent carbons.
4. Step 4: Dehydration of the β-hydroxy ketone. Under the reaction conditions, the β-hydroxy ketone undergoes elimination of water (dehydration) to form an α,β-unsaturated ketone. This step involves the formation of a double bond between the α and β carbons.
5. Step 5: Predict the final product. After dehydration, the product will be an α,β-unsaturated ketone where the benzaldehyde-derived phenyl group (Ph) is attached to the β-carbon of the unsaturated ketone. The structure of the product can be represented as Ph-CH=CH-COCH3.

Key Concepts

Aldol Condensation

Aldol condensation is a reaction between aldehydes or ketones that contain at least one alpha-hydrogen. In this process, two carbonyl compounds react in the presence of a base to form a beta-hydroxy aldehyde or ketone, which can further dehydrate to yield an alpha, beta-unsaturated carbonyl compound. This reaction is crucial in organic synthesis for forming carbon-carbon bonds.

Dehydration Reaction

Dehydration in the context of aldol condensation refers to the elimination of a water molecule from the beta-hydroxy aldehyde or ketone product. This step typically occurs under heat or acidic conditions, resulting in the formation of a more stable alpha, beta-unsaturated carbonyl compound. Understanding this step is essential for predicting the final products of the aldol condensation.

Mechanism of Aldol Reaction

The mechanism of the aldol reaction involves several key steps: the formation of an enolate ion from a carbonyl compound, nucleophilic attack of the enolate on another carbonyl compound, and subsequent protonation to form the beta-hydroxy carbonyl. This understanding of the mechanism is vital for predicting the structure of the products and the stereochemistry involved in the reaction.