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Researcher

Matthew McBride

Objective

To synthesize trans-dibenzalacetone using an ethanol/water (1:1)vol solvent and sodium hydroxide as the catalytic base.

Procedure

Dissolve 2 g of NaOH in 10 mL of distilled water. Add 10 mL of ethanol to the solution. Create a 2:1 molar solution of acetone and benzaldehyde with benzaldehyde being the limiting reagent (1M). Add the acetone and benzaldehyde solution to the ethanol solution drop-wise and allow the solution to stir for 1 hour. Recrystallize the crude product from ethanol.
Reaction Preparation Sheet

Results

Characterization of Product 282A
Amount: 1.7983 g
Appearance: Dark orange solid
HNMR Spectrum
Purity: Very impure and still wet from ethanol

Characterization of Product 282B
Amount: 1.577 g
Appearance: Yellow powder with dark orange clumps
HNMR Spectrum
Purity: Very impure

Discussion

The recovered product was impure likely from sodium carbonate formed from the NaOH reacting with the CO2 in air. The recovered yield was 51%, but it was not pure trans-dibenzalacetone.

Conclusion

Recovered 1.7983 g of impure trans-dibenzalacetone for a reaction yield of 51%. The product likely contains sodium carbonate.

Log

2012-07-13

12:52 1.9426 g of NaOH pellets were added to a 50 mL Erlenmeyer flask.
13:02 Added 10 mL of distilled water to the flask. Stirred the solution on the stir plate to dissolve the pellets. The pellets dissolved within two minutes.
13:04 Added 10 mL of ethanol to the stirring solution.
13:14 Added 0.8910 g of acetone to a 5-dram snap cap vial.
13:17 Added 3.4171 g of benzaldehyde to the 5-dram vial with the acetone.
13:20 The acetone and benzaldehyde mixture in the 5-dram vial was added drop-wise to the 50 mL flask as the solution was stirring. The reaction mixture first obtained a clear yellow colored solution, but within 2 minutes yellow crystals began to form and the reaction mixture became a thick yellow solution. The mixture was left on the stir plate.
14:20 The falsk was removed from the stir plate. The solution was thick and had lots of yellow crystals visible. The solution was filtered using a Buchner funnel and suction filtration. The yellow crude product was captured on the filter paper and left on the suction to dry.
14:24 The crude product was gently poked with a spatula to separate the crystals and allow all of the crystals to dry.
14:35 The crude product weighed 5.3101 g and was placed in a 50 mL Erlenmeyer flask. 15 mL of ethanol was added to the flask and the solution was placed on the stir plate and heat to dissolve the crude product into the solution.
14:45 The solution obtained a darker orange color and the crystals were observed to be entering the solution. 5 mL of ethanol was added to the solution.
14:53 An additional 5 mL of ethanol was added.
14:55 The solution began to boil and it was observed that all of the crystals had entered the solution. The solution had a very dark orange color. The flask was removed from the hot plate and placed on the hood counter to allow the solution to cool to room temperature.
15:15 Placed the flask on ice to cool. Still a very dark solution and not many crystals visible.
15:47 The solution in the flask was filtered (a dark orange solid was present, not really crystals). Placed the recovered solid in a 5-dram vial. The 5-dram vial weighed 11.8611 g empty and 13.6594 g with the product. This is Product 282A.
16:00 0.0764 g of Product 282A was added to a 1-dram snap cap vial. 0.4 mL of CDCl3 was added to the vial. Some solid was present in the vial and did not dissolve into the CDCl3. The sample was analyzed by 500MHz HNMR and the files of the spectrum saved as UCEXP282_A.

2012-07-17

10:26 35.202 g was the weight of an empty 25 mL round bottom flask.
10:31 Added approximately 7-8 mL of dichloromethane to the vial holding Product 282A. Solid was visible in the solution, but some of the yellow solid dissolved in.
10:42 The solid was filtered out using a piece of kimwipe stuffed into a Pasteur pipette. The solution was filtered into the 25 mL round bottom flask.
10:47 The round bottom was attached to the rotary vacuum to evaporate the dichloromethane.
11:03 A yellow foam appeared in the bottom of the round bottom flask.
11:11 The flask was removed from the rotary vacuum. A thick yellow sticky paste was at the bottom of the flask (Product 282B). The weight of the flask with the product was 36.832 g. The flask was placed in the hood.
13:13 The flask with product was weighed to be 36.779 g.
13:25 0.1324 g of Product 282B was placed in a 1-dram snap cap vial and 0.4 mL of CDCl3 was added to the vial. A piece of solid did not dissolve immedately into the solution. The solution had to be stirred vigorously before the solid dissolved into solution.
13:31 The sample was transferred to NMR Tube 2 and analyzed by 500MHz HNMR. The spectrum was saved as UCEXP282_B.