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Researcher

Matthew McBride

Objective

To synthesize trans-dibenzalacetone from benzaldehyde and acetone and recrystallize the product from ethyl acetate.

Procedure

Potassium hydroxide pellets were dissolved in water and then ethanol was added to the solution. The solution was cooled and acetone was slowly added to the solution, as the solution was constantly stirred. Benzaldehyde (1.2M in approximately 20 mL reaction mixture) was then added to the solution and the solution was allowed to stir for 15 minutes. The product was captured by suction filtration and was was washed with water and ethanol. The product was then recrystallized from ethyl acetate. The following Prep Sheet was used to prepare this reaction.

Results

The SAMS sheet containing the HNMR spectrum of the product can be found here

Picture #1: The solution when the reaction first started (Note: The white color in the center is from the stir bar and not part of the solution)
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Picture #2: The solution after the reaction had progressed for at least 15 minutes
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Picture #3: The crude product captured by the suction filtration
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Picture #4: The crude product in the flask prior to recrystallization
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Picture #5: The product after recrystallization from ethyl acetate
EXP279Picture#5.png

Discussion

1.5481g of trans-dibenzalacetone was recovered from this synthesis. Based on the reaction preparation sheet, the predicated about of product was 2.809g. The amount of reactants used was not exactly the amounts listed in the prep sheet, but this still shows that the reaction obtained an approximately 55.11% yield.

Previous experiments that had attempted this reaction were EXP269, EXP274, and EXP278, but each were not successful for different reasons. The primary finding is that the amount of ethanol must be great enough to dissolve all of the benzaldehyde into the solution or the reaction will not take place. The amount of ethanol should be approximately equivalent to the amount of water added to the solution.

The trans-dibenzalacetone can now be used to measure solubility in five different solvents in order to generate predictions for the solubility of this compound in organic solvents.

Conclusion

This reaction was successfully completed and 1.5481g of trans-dibenzalacetone was synthesized.

Log

2012-04-09

10:33 1.777g of potassium hydroxide pellets were added to a 50mL Erlenmeyer flask.
10:36 Added 6mL of distilled water to the flask and swirled the flask until the pellets dissolved.
10:38 Added 6mL of ethanol to the flask. A stir bar was added to the flask and it was placed on the stir plate.
10:43 The flask was removed from the stir plate and placed on the ice bath to cool.
10:50 The flask was placed back on the stir plate and 1mL of acetone was added to the flask. The acetone was slowly over about 30 seconds.
10:55 2.5mL of benzaldehyde was added to the flask. The solution initially turned a clear yellow color, but within 30 seconds formed a cloudy orange solution. Picture #1 was taken. The solution was allowed to mix on the stir plate for at least 15 minutes.
11:19 Pictures #2 and #3 were taken.
11:24 The solution in the flask was filtered using a sintered glass filter and a suction flask. The product that was formed by the reaction was captured by the filter and filter paper. The crystals were washed twice with distilled water and then were washed with cooled ethanol. The crystals were allowed to dry by sitting on the filter. Picture #4 was taken.
11:40 The crude product (looked to be about approximately 3g) was placed in a 50mL Erlenmeyer flask. 7mL of ethyl acetat was added to the flask. The flask was placed on the hot plate and was heated and stirred to allow the crystals to dissolve into the ethyl acetate in order to be purified by recrystallization.
11:43 All of the solid was observed to have entered the ethyl acetat solution.
11:45 The flask was removed from the hot plate and allowed to cool inside the hood at room temperature.
11:51 The flask was placed on ice to cool the solution further.
11:59 The weight of the empty 4-dram vial was 11.7830g.
12:04 Yellow crystals were visible in the solution in the flask on ice.
12:07 The solution was filtered to capture the crystals. The crystals were washed twice with water and allowed to dry on the filter. Picture #5 was taken.
12:12 The crystals were removed from the filter and placed in the 4-dram vial. Picture #6 was taken.
12:43 The weight of the vial with the recovered product was 13.3311g.
12:55 0.0911g of the product was placed in a 1-dram vial.
12:57 Approximately 1mL of CDCl3 with TMS was added to the 1-dram vial. The product was observed to immediately dissolve into the solution.
13:02 The solution was added to an NMR tube and analyzed by 500MHz HNMR.