Aldol Condensation Protocol for Dibenzalacetone

Research will be limited to:
- Reactants: Benzaldehyde and Acetone
- Product: Dibenzalacetone
- Reaction: Aldol Condensation
- Catalyst: NaOH (specified concentration needed)
- Purification: Recrystallization from Ethanol

Strategy: The user wants a detailed, step-by-step laboratory protocol for the synthesis of dibenzalacetone via aldol condensation. I need to find specific quantitative details: the exact concentration and volume of NaOH used, the specific addition rate (e.g., dropwise), the order of addition (benzaldehyde/acetone mixture into NaOH or vice versa), the reaction temperature, stirring duration, and the expected yield and melting point after recrystallization from ethanol. I will search for academic lab manuals or organic chemistry procedures that provide these specific parameters.
Queries:
- dibenzalacetone synthesis protocol NaOH concentration volume addition rate temperature
- dibenzalacetone recrystallization ethanol procedure yield melting point

🔍 Reading and summarizing 5 new websites...

1. Dibenzalacetone - Organic Syntheses Procedure
2. [PDF] 23. The Aldol Condensation: Synthesis of Dibenzalacetone
3. [PDF] Dibenzalacetone by Aldol Condensation 49
4. Aldol Condensation: Preparation of Dibenzalacetone (1,5-Diphenyl ...
5. Preparation of Dibenzal Acetone - BYJU'S

Found 5 websites. Summarized content:

Dibenzalacetone - Organic Syntheses Procedure
Step-by-step protocol for the aldol condensation synthesis of dibenzalacetone from benzaldehyde and acetone:

1. Reactants: Benzaldehyde (106 g, 1 mole) and Acetone (29 g, 0.5 mole)
2. Catalyst: Sodium hydroxide (NaOH), 100 g in 1 L of water and 800 cc of alcohol
3. NaOH Concentration: Not explicitly stated, but prepared by dissolving 100 g NaOH in 1 L water and 800 cc alcohol.
4. Volume: Total volume of NaOH solution is 1.8 L (1 L water + 0.8 L alcohol).
5. Addition Rate and Order:
   • Prepare a cooled solution of NaOH in water and alcohol.
   • Add one-half of the benzaldehyde-acetone mixture to the NaOH solution while stirring vigorously.
   • After 15 minutes, add the remaining benzaldehyde-acetone mixture, rinsing the container with a little alcohol.
6. Temperature: Maintain the reaction mixture at 20-25°C using a water bath.
7. Stirring Time: Stir vigorously during the addition of reactants. Continue stirring for 30 minutes after the complete addition.
8. Vacuum Filtration: Filter the resulting mush (precipitate) with suction using a large Büchner funnel.
9. Washing: Wash the filtered product thoroughly with distilled water.
10. Drying: Dry the product at room temperature to constant weight.
11. Recrystallization (Purification): Recrystallize the crude dibenzalacetone from hot ethyl acetate, using 100 cc of ethyl acetate for each 40 g of dibenzalacetone.
12. Ethanol: Not used for recrystallization according to this source, but used as a solvent for the sodium hydroxide solution in addition to water.
13. Yield: 105-110 g (90-94% of the theoretical amount). Allowing the mush to stand several hours, chilled, and filtered cold increase the yield slightly, 93%.
14. Melting Point:
    • Crude product: 104-107°C.
    • Recrystallized product: 110-111°C.

[PDF] 23. The Aldol Condensation: Synthesis of Dibenzalacetone
Based on the provided document, here's a step-by-step protocol for the aldol condensation synthesis of dibenzalacetone from benzaldehyde and acetone:

Reactants: Benzaldehyde and Acetone

Product: Dibenzalacetone

Reaction: Aldol Condensation (Claisen-Schmidt Reaction)

Catalyst: Aqueous NaOH (10% solution)

Procedure:

1. Prepare Acetone/Ethanol Solution: Add 1 mL of ethanol to a small vial. Add seven drops of acetone to the vial, cap it, and shake to mix. Weigh the vial to determine the mass of acetone added.
2. Calculate Benzaldehyde Amount: Based on the mass of acetone used, calculate the necessary mass of benzaldehyde (a slight excess is okay).
3. Reaction Setup: Add the calculated amount of benzaldehyde to a 3 mL conical vial containing a spin vane. Transfer the acetone/ethanol solution to this vial using a pipette. Place a septum and cap on the vial and begin stirring.
4. NaOH Addition: Remove the cap and add 0.5 mL of 10% aqueous NaOH solution over a period of 5 minutes with stirring.
5. Reaction Time: After NaOH addition is complete, cap the vial and allow it to stir rapidly for 25 minutes. Dibenzalacetone will precipitate as a solid.
6. Filtration and Washing: Collect the solid via Hirsch filtration and wash it several times with small portions of cold water.
7. Air Dry: Allow the solid to air dry by continuing to apply vacuum for 2-3 minutes.

Purification:

1. Recrystallization: Recrystallize the solid by dissolving it in 2 mL of hot ethanol.
2. Cooling: Allow the solution to cool slowly at room temperature, and then in an ice bath.
3. Filtration: Collect the crystals by Hirsch filtration.

Analysis:

Calculate the yield, determine the melting point, and record an IR and 1H NMR spectrum of the product.

[PDF] Dibenzalacetone by Aldol Condensation 49

Aldol Condensation Synthesis of Dibenzalacetone

Reactants:

• Benzaldehyde (excess, 2.2 equivalents relative to acetone)
• Acetone (limiting reagent, 0.0125 mol)

Catalyst:

• NaOH-Ethanol-Water solution mixture (premixed, 50 mL) - Concentration not specified in document

Procedure:

1. Reaction Setup: Use a 125-mL Erlenmeyer flask with a magnetic stirring bar. Add 50 mL of the NaOH-Ethanol-Water solution mixture. Place the flask on a magnetic stirrer and adjust for even stirring.
2. Addition of Reactants: Add the calculated amount of benzaldehyde to the flask using a syringe. Add the calculated amount of acetone last, using a syringe.
3. Reaction Monitoring: Observe and record the time it takes for the solution to turn yellow and then become cloudy, with solid accumulating.
4. Reaction Time: Let the solution stir for 30 minutes.
5. Filtration: Add 20 mL of water to the mixture. Filter the mixture, pouring the filtrate into a waste container.
6. Washing: Wash the crystals three times with 50 mL of water each time.
7. Drying (Crude): If crystals are wet, press them drier with filter paper.
8. Weight (Crude): Weigh the crude product and save a small crystal for melting point determination. (Yield may be >100% due to residual water).

Recrystallization:

1. Hot Water Bath: Prepare a hot water bath (400-mL beaker, hot plate ~5).
2. Dissolving: Purify the crystals by recrystallizing from ethanol in a 125-mL Erlenmeyer flask inside the hot-water bath. Start with ~4mL ethanol /gram product and heat. Add more hot ethanol to increase solubility, or hot water to reduce solubility as needed. Be careful not to mistake melting for dissolving.
3. Cooling & Rinsing: After cooling, rinse the crystals with an appropriate rinse solvent (unspecified in document).
4. Drying (Recrystallized): Dry thoroughly.

Analysis:

• Determine the yield and melting point of the recrystallized product. Calculate the % yield.
• Determine the melting point of the crude product.

Expected Product Properties:

• Dibenzalacetone
• Melting Point: Somewhere between 80 and 120 ºC
• Molecular weight: 234 g/mol

Aldol Condensation: Preparation of Dibenzalacetone (1,5-Diphenyl ...

Aldol Condensation Synthesis of Dibenzalacetone Protocol:

Reactants: Benzaldehyde and Acetone

Product: Dibenzalacetone (1,5-diphenyl-1,4-pentadien-3-one)

Reaction: Aldol Condensation (specifically, Claisen-Schmidt condensation)

Catalyst: Aqueous ethanolic sodium hydroxide (NaOH). The stock reagent for the entire lab is made by dissolving 24.0 g NaOH pellets in 240 mL of water and, after the pellets are dissolved, adding 180 mL of 95% ethanol. Make immediately before use. If a lab stock solution is not prepared, or it has been used, each student group can prepare his own solution by dissolving 1.8 g NaOH in 18.0 mL water and then adding 13.5 mL 95% ethanol. (Excess solution should be disposed of properly after the lab.) A quantity of 25 mL of the NaOH solution is needed.

Step-by-step Procedure:

1. Combine Reactants: In a 50-mL round-bottom flask with a curved magnetic stirring bar, combine 2.40 mL benzaldehyde and 0.90 mL acetone.
2. Add Catalyst: Add 25 mL of aqueous ethanolic sodium hydroxide solution to the reaction mixture.
3. Stirring: Stir the reaction mixture at room temperature for 30 minutes. A yellow solid should precipitate. If a precipitate does not form, stir it vigorously with a spatula or stirring rod and wait up to an hour.
4. Vacuum Filtration: Collect the crude product using vacuum filtration in a Büchner funnel. Wash any remaining solid from the flask with a small amount of cold water and add to the funnel. Wash the precipitate (in the funnel) with a small amount of the water.
5. Washing: Transfer the solid product to a beaker, add 20 mL of 5% acetic acid in ethanol, stir, and filter again through a Büchner funnel. Wash the solid in the funnel with a small amount of cold ethanol.
6. Drying: Label the solid material and store it in the drying oven until the next lab period.
7. Recrystallization: Recrystallize the dried product from about 20 mL of hot, boiling 95% ethanol. Dissolve the solid in a minimum volume of the hot ethanol, allowing crystals to reform as the solution cools to room temperature. If too much ethanol is used, evaporate down to about 15 mL to induce crystallization. Alternatively, ethyl acetate can be used as the recrystallization solvent.
8. Filtration and Drying: Collect the crystallized solid by filtration using a Büchner funnel. Allow the solid to dry in the funnel for 10-15 minutes with vacuum applied to evaporate the solvent.
9. Product Analysis: Determine the mass of the dry product and calculate the percent yield. Determine the melting point and compare it to the literature value of 107 °C.

Yield: Determine percent yield based on the limiting reagent.

Melting Point: Expected melting point of dibenzalacetone is 107 °C.

Preparation of Dibenzal Acetone - BYJU'S

Step-by-Step Protocol for Dibenzalacetone Synthesis from Benzaldehyde and Acetone

Reaction: Aldol Condensation (Claisen-Schmidt reaction)

Reactants: Benzaldehyde, Acetone

Product: Dibenzalacetone

Catalyst: Sodium hydroxide (NaOH)

Procedure:

1. Reactant Mixing: Add 10 mL of freshly distilled benzaldehyde and 20 mL of acetone to a conical flask.
2. Catalyst Addition: Place the flask in a cold water bath. Add 2.5 mL of NaOH solution dropwise with constant stirring.
3. Temperature Control: Maintain the temperature at 30°C.
4. Reaction Time: After completing the NaOH addition, stir the mixture for 2 hours.
5. Neutralization: Add dilute hydrochloric acid to the reaction mixture. Transfer the mixture to a 250 mL separating funnel.
6. Extraction: Add 20 mL of chloroform/ether to the mixture and shake thoroughly. Remove the organic layer and repeat the process twice.
7. Crystallization: Cool the mixture in ice-water. Dibenzalacetone separates initially as a fine emulsion and then forms yellow crystals.
8. Distillation (Optional): Distill the residual portion under pressure and collect the fraction boiling at 150°C (Purpose unclear, may not be necessary)
9. Washing & Drying: Wash the pale yellow crystals with cold water and dry them.
10. Recrystallization: Crystallize the product with ethanol.

Purification:

• Recrystallization from ethanol.

Observations:

• Color of Crystals: Pale Yellow
• Expected Yield: 4g
• Melting Point: 112°C

Precautions:

• Release pressure from the flask periodically if a vigorous reaction occurs.
• Do not exceed a temperature of 30°C.
• Keep ethanol and acetone away from flames.

Note: The website does not specify the concentration of NaOH to use. Also the volume of ethanol and addition rate for recrystallization are not indicated.