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Researcher

Matthew McBride

Objective

To synthesize trans-dibenzalacetone from benzaldehyde and acetone.[link to procedure followed JCB]

Procedure

Add ethanol to a 10% potassium hydroxide solution and a 20% potassium hydroxide solution in separate 500mL Erlenmeyer flasks. Ethanol will be added to each of these solutions. Benzaldehyde (0.43M in approximately 550 mL of reaction mixture and the limiting reagent) will be added to each solution and then acetone will be slowly added to each flask. The solutions will be stirred on the stir plate to allow the reaction to be completed. Orange crystals of trans-dibenzalacetone should form as the reaction proceeds. The trans-dibenzalacetone product will be separated from the solvent and recrystallized from ethanol to purify the product.

Results

No product was recovered in this experiment and will be repeated on a smaller scale.

Here is the spreadsheet that was used to prepare this reaction and to determine the amount of addition of the different reagents: Reaction Preparation Spreadsheet

Discussion

Trans-dibenzalacetone is a common compound synthesized in introduction organic chemistry labs. It has been used for many years by many different universities. However, little to no information is available regarding the solubility of trans-dibenzalacetone in different solvents. Since this product is used in many labs, it would be valuable to have an idea of the solubility of this product especially when a solvent must be chosen with which to purify the trans-dibenzalacetone. First, the product must be synthesized and that is the purpose of this experiment, but once the product is obtained, the solubility of the trans-dibenzalacetone will be measured in five organic solvents so that the Abraham model may be used to predict the solubility of trans-dibenzalacetone in many different solvents.

There are a few reasons that this experiment may have not obtained a product. For the future experiment, the KOH and water will be mixed together and the solid KOH will be completely dissolved in the solution before the ethanol is added. In a similar manner, the benzaldehyde will be thoroughly mixed into the solution prior to the addition of acetone to ensure that the acetone is reacting with the benzaldehyde.

Conclusion

The reaction likely failed because the benzaldehyde could not be fully solubilized with the amount of ethanol used relative to water. This synthesis was successfully completed in EXP279 with 1:1 ethanol/water, compared to only 1:6 ethanol/water used in this experiment.

Log

2012-03-12

12:25 Added 28g of KOH to each of 500mL Erlenmeyer flasks.
12:33 Added 30mL of ethanol to each flask.
12:46 Added an additional 28g of KOH to flask 2 so that the flask had a total of 56g of KOH.
12:53 Added 180mL of distilled water to each flask.
13:11 Added 10mL of benzaldehyde to each flask. This value is approximate because there was difficulty with the needle used to remove the benzaldehyde from the glass bottle.
13:19 Placed flask 2 on the stirrer and the solution was observed to turn an orange color.
13:22 Place flask 1 on an old stir plate that did not stir the solution very well.
13:41 Removed beaker two from the stir plate and placed on ice. The solution was observed to separate into two layers. A thin top layer that looked oily and was of a orange color. The bottom layer was of a pale yellow color. No crystals were observed to form.
14:00 No crystals were visible in either flask and it was determined that the reaction had not been completed.