Preparation of Dibenzalacetone

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PREPARATION OF DIBENZALACETONE Stochiometric reaction: Benzaldehyde Acetone Dibenzalacetone Mechanism: Step 1: In the first step, an acid-base reaction occurs. Hydroxide acts as a base and removes the acidic α-hydrogen resulting in the reactive enolate. Step 2: The nucleophilic enolate attacks the aldehyde at the electrophilic carbonyl carbon in a process similar to nucleophilic addition to give an intermediate alkoxide. Step 3: An acid-base reaction occurs. The alkoxide deprotonates a water molecule resulting in a hydroxide and the β−hydroxyaldehydes or aldol product. Objectives: • To synthesize dibenzalacetone by the base-catalysed aldol condensation reaction of acetone with benzaldehyde. • Recrystallization and characterization of the product obtained by measuring its melting point. Method: 1. A solution of 0.453g sodium hydroxide in 2mL water and 2mL 95% ethanol was made in an Erlenmeyer flask. 2. The solution was allowed to cool to room temperature. 3. 0.312g of acetone was added to the solution. 4. 0.76g of benzaldehyde was added to the solution resulting in a yellow turbidity which quickly changed to a precipitate. 5. The flask containing the solution was swirled from time to time over a period of 15 minutes. 6. A Buchner funnel was used to collect the crude product which was first washed with water and then a small amount of ice-cold 95% ethanol. 7. The crude product was placed in an Erlenmeyer flask. 8. Ethylacetate was placed in a small beaker and heated until boiling point. 9. The boiling ethylacetate was added to the crude product in small amounts at a time. After each amount was added the product was heated. Just enough ethylacetate was added to dissolve the crude product. 10. The mixture was allowed to cool to room temperature and the product began to precipitate from the solution. 11. The

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