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Researcher

Matthew McBride

Objective

To synthesize trans-dibenzalacetone using the procedure followed in EXP279 and indicated in this teaching manual

Procedure

Potassium hydroxide pellets are dissolved into water and then ethanol is added in an equal amount to the water. The solution is cooled and then acetone is added to the solution as it is stirring. Benzaldehyde (1.1M in the approximately 100 mL reaction mixture and limiting reagent) is added to the solution in a 2:1 molar ratio to acetone. The crude product is recovered by filtration and recrystallized from ethanol. The following Reaction Preparation Sheet was used to carry out the reaction.

Results

No product was recovered from the recrystallization of the crude product.

Discussion

The yellow trans-dibenzalacetone crystals were clearly visible in the reaction mixture and captured as crude product. When it was attempted to recrystallize the product from ethanol, none of the crystals came out of the solution. A very thick paste formed on the bottom of the flask, but not crystals.

Conclusion

No trans-dibenzalacetone was recovered from this reaction

Log

2012-06-26

16:49 8.948 g of potassium hydroxide pellets were added to a 125 mL Erlenmeyer flask.

2012-06-27

11:52 Added 32 mL of distilled water to the flask. Stirred the flask until the pellets dissolved.
11:55 Added 32 mL of ethanol to the falsk. Added a stir bar and placed on the stir plate.
12:02 Placed the flask on the ice bath to cool.
12:08 Removed the flask from the ice bath and placed back on the stir plate. Added 5 mL of acetone to the reaction mixture.
12:11 Added 12 mL of benzaldehyde to the reaction mixture. The solution obtained an organe color. Picture #1 was taken.
12:14 Solution became a thick yellow solution.
12:26 The solution was filtered using a Buchner funnel and suction filtration. The crude product was washed with cooled ethanol. Picture #3 was taken.

2012-06-29

12:08 Transfered the crude product from the Buchner funnel to a 250 mL flask. The weight of the flask empty was 114.045 g and the weight of the flask with the crude product was 132.290 g. The crude product weighed 18.245 g.
12:20 Approximately 40 mL of ethanol was added to the flask, a stir bar was added, and the flask was placed on the hot plate to heat and stir.
12:28 An additional 25 mL of ethanol was added to the flask.
12:30 The solution obtained a dark orange color - very few crystals remained in the solution. Picture #4 was taken.
12:37 The flask was removed from the heat. All the crystals had entered the solution. The solution was boiling slightly. The flask was allowed to cool to room temperature.
12:46 The solution had a very dark color. Picture #5 was taken. No crystals were visible. The flask was placed in an ice bath to cool.
13:27 No crystals come out of the solution. Picture #6 was taken. No crystals were recovered from the solution. A thick, yellow, paste like substance lined the bottom of the flask, but no crystals were present.