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Researcher

Matthew McBride

Objective

To synthesize trans-dibenzalacetone from acetone and benzaldehyde in an ethanol solvent following the procedure described by this article

Procedure

2 g of sodium hydroxide pellets were dissolved in ethanol. A mixture of 8 mL of ethanol, 0.8 mL of acetone, and 2.0 mL of benzaldehyde was created in a separate flask. 5 mL of the NaOH solution was added to the reaction mixture and allowed to stir for 15 minutes. The crude product was captured by suction filtration using a Buchner funnel. The crude product was recrystallized from ethanol. This is the Reaction Preparation Sheet used for this reaction.

Results

Characterization of Product 314A
Amount: 0.4515 g
Appearance: Yellow crystals
Was combined with Product 314B to form Product 314C

Characterization of Product 314B
Amount: 0.1669 g
Appearance: Yellow crystals
Was combined with Product 314A to form Product 314C

Characterization of Product 314C
Amount: 0.183 g
Appearance: Yellow solid
HNMR Spectrum
Purity: Very pure sample with only a trace amount of acetone and dichloromethane present.
This Product 314C was all of the trans-dibenzalacetone recovered from this reaction

Discussion

The reactants used were 20 mmol of benzaldehyde and 10 mmol of acetone (0.667M in a solution of total volume 15 mL) and this should have formed 10 mmol of trans-dibenzalacetone. This reaction recovered 0.183 g of trans-dibenzalacetone in high purity following recrystallization from ethanol for a yield of 8%.

The NaOH reacted with the CO2 in the air to form the white solid precipitate sodium carbonate. This had to be removed by dissolving in dichloromethane and then evaporating the dichloromethane. This procedure will be repeated using an organic base, such as Triethylamine or another 2° amine, as the base to avoid the issue of NaOH forming sodium carbonate. These different procedures to form trans-dibenzalacetone are being attempted to avoid using water in the solvent for the reaction.

Conclusion

0.183 g of pure trans-dibenzalacetone was synthesized from a 2:1 molar ratio of acetone and benzaldehyde in an ethanol solvent for a reaction yield of 8%.

Log

2012-07-10

10:26 2.003 g of NaOH pellets were added to a 50 mL Erlenmeyer flask.
10:37 8 mL of ethanol was added to the flask and the flask was placed on the stir plate with a stir bar to dissolve the pellets in the ethanol.
10:51 10 mL of ethanol was added to the flask as it stirred on the stir plate.
11:01 10 mL of ethanol was added to the flask as it stirred on the stir plate.
11:05 10 mL of ethanol was added to the flask as it stirred on the stir plate. Pellets were still visible in the solution.
11:18 The heat was turned on to heat the solution to dissolve the pellets.
11:25 The solution was transfered to a 125 mL Erlenmeyer flask (Flask #1). And 10 mL of ethanol was added.
11:28 10 mL of ethanol was added to the flask as it stirred on the stir plate.
11:32 20 mL of ethanol was added to the flask as it stirred on the stir plate. Pellets were still visible.
11:35 All the pellets were observed to have entered the solution.
11:37 8 mL of ethanol was added to a second 125 mL Erlenmeyer flask (Flask #2).
11:45 0.8 mL of acetone and 2 mL of benzaldehyde was added to Flask #2. This solution was stirred on the stir plate using a stir bar. 5 mL of the NaOH solution from Flask #1 was added to the solution.
11:51 Yellow crystals were visible in Flask #2.
12:40 The flask was removed from the stir plate and the thick yellow solution was filtered using a Buchner funnel. 4-5 mL of ethanol was used to make the transfer. The crude product was yellow and allowed to dry on the filter paper. This was Product 314A
12:51 0.0902 g of Product 314A was placed in a 1-dram snap cap vial. This is Vial 1.
12:55 Approximately 1 mL of CDCl3 was added to Vial 1 with Product 314A. The solid product did not fully dissolve in the CDCl3. Solid was visible in the solution.
12:57 Two layers formed in Vial 1. A top layer containing the solid and the bottom layer that was just liquid.
13:04 The remaining crude product (0.4515 g of 314A) was added to a 25 mL Erlenmeyer flask. 5 mL of ethanol was added to the flask as well as a stir bar the the flask was placed on the hot plate to mix and heat.
13:23 2 mL of ethanol was added to the flask.
13:29 The solution was boiling and 2 mL of ethanol was added to the solution. All of the crystals were observed to have entered the solution. The flask was removed from the hot plate and allowed to cool to room temperature.
13:41 Crystals were visible in the flask. The flask was placed in a ice bath to cool further.
14:08 The flask was removed from the ice bath. Yellow crystals were visible in the solution. The solution was filtered using a Buchner funnel and suction filtration.
14:12 Yellow crystals were captured on the filter paper. There appeared to be a small amount of white solid visible among the yellow crystals. This is Product 314B.
14:21 0.0604 g of Product314B was placed in a 1-dram snap cap vial and 0,5 mL of CDCl3 was added to the vial. Solid was visible in the vial. An empty vial weighed 4.7111g and the vial with the remaining crystals of Product 314B was 4.8780 g for a total of 0.1669 g of Product 314B.

2012-07-11

10:09 The weight of an empty 25 mL round bottom flask was weighed to be 35.2042 g.
10:16 All of the contents from Vial 1 (crude product in CDCl3), Vial 2 (purified product in CDCl3), and Vial 3 (purified product) were combined into a 5-dram snap cap vial. This is Vial 4.
10:22 Added 2 mL of dichloromethane to the 5-dram vial. Some white solid was visible in the solution and this was likely sodium carbonate.
10:55 A small piece of kimwipe was stuffed into a pasteur pipette to form a filter. The solution in Vial 4 was pipetted through the pipette filter into the 25 mL round bottom flask. The white solid was removed by the liquid passed through to the round bottom flask. A small amount of air was used to provide pressure to push all of the liquid through the filter. The solution in the round bottom flask was yellow and contained no solid.
11:16 The round bottom flask was placed on the rotary vacuum until all of the liquid had evaporated and only yellow solid remained at the bottom of the flask. CDCl3 boils at 61°C and dichloromethane boils at 40°C, so these two liquids evaporated easily.
11:25 The weight of the round bottom with yellow solid product (Product 314C) on the bottom of the flask was 35.387 g. This means there was 0.183 g of trans-dibenzalacetone recovered.
11:29 Approximately 0.4 mL of CDCl3 was added to the round bottom flask and all of the yellow solid was observed to dissolve into the solution. This solution was transferred to NMR Tube 1. This sample was analyzed by 500MHz HNMR and the file of the spectrum was saved as ONSEXP314_ProductC