dba scheme .png

Researcher

Matthew McBride

Objective

To synthesize trans-dibenzalacetone from benzaldehyde and acetone.

Procedure

A 10% potassium hydroxide solution was created. Ethanol was added to this solution and the solution was cooled in an ice bath. Benzaldehyde (0.33M in approximately 33 mL reaction mixture and limiting reagent) was added to the solution and then acetone was added. The solution was allowed to mix for 30 minutes. The solution was cooled on an ice bath and then the product was filtered off using suction filtration.

Results

The following Reaction Preparation Sheet was used to complete this synthesis. No product was obtained.

Picture #1: The solution moments after the acetone was added to the benzaldehyde
ONSEXP278Picture1.png

Picture #2: The Hirsch funnel with the piece of filter paper used
ONSEXP278Picture2.png

Picture #3: The solution after 30 minutes of mixing to allow the reaction to take place
ONSEXP278Picture3.png

Picture #4: The orange bubble layer that formed rather than product
ONSEXP278Picture4.png

Discussion

The solution formed an orange oily bubble layer (picture #4) rather than crystals of dibenzalacetone. It is believed that not enough ethanol was added to the solution for the benzaldehyde to dissolve into the solution and this resulted in the formation of the bubbles. To correct and prevent this, a future experiment will use a greater amount of ethanol. This problem did not occur in EXP274 when product was obtained from the reaction, but only 0.5mL of acetone was used in this experiment, while 0.75mL of acetone was used in this experiment. It is possible that this difference could have contributed in some way, but more likely that the lack of ethanol was the cause.

Conclusion

Product was not obtained and more ethanol will be used in a future experiment in an attempt to correct this issue.

This synthesis was successfully completed in EXP279

Log

2012-04-04

11:24 5.646g of potassium hydroxide pellets were added to a 50mL Erlenmeyer flask.
11:28 18mL of distilled water was added to the flask and a stir bar was placed in the flask. The flask was placed on the stir plate and mixed.
11:29 All the pellets were dissolved and the solution was clear.
11:31 7.5mL of ethanol was added to the flask as it was mixing on the stir plate.
11:35 The flask was removed from the stir plate and placed on ice to cool.
11:40 1mL of benzaldehyde was added to the flask and the flask was placed back on the stir plate to mix.
11:45 0.75mL of acetone was added to the solution. The solution was clear when the acetone was first added, but obtained a yellow color within 30 seconds of the addition of the acetone. Picture #1 was taken now and shows the yellow color of the solution. The solution was allowed to mix throughly for 30 minutes.
11:55 A piece of filter paper was cut out and placed on the Hirsch funnel to cover all the holes of the funnel. The suction flask was attached to the vacum. Picture #2 was taken. The filter paper was flat along the surface of the funnel.
12:17 Picture #3 was taken. This is what the solution looked like after 30 minutes of mixing. It still had a yellow color, but there was a slight shade of orange visible.
12:18 The flask was placed on the ice bath to cool.
12:28 Orange bubble layer formed on the top of the solution. No crystals were visible in the solution. Picture #4 was taken.
12:38 An additional 10mL of ethanol were added to the flask and the solution was mixed.
12:51 The flask was removed and placed on an ice bath.
12:55 The solution was poured through the Hirsch funnel to be filter out any crystals in the solution.
13:02 The filtration was completed, but there was no product obtained.