dba scheme .png

Researcher

Matthew McBride

Objective

To synthesize trans-dibenzalacetone from acetone and benzaldehyde in an ethanol solvent using piperidine as the catalytic base

Procedure

Piperidine was added to ethanol and this solution was mixed. In a separate vial, benzaldehyde and acetone were added together in a 2:1 molar ratio. This benzaldehyde and acetone mixture was added drop-wise to the ethanol solution. The solution was then refluxed until the yellow product crystals formed. The reaction was monitored by HNMR. The following
Reaction Preparation Sheet was used to plan the synthesis.

Results

The following HNMR Spectrums show the contents of the reaction mixture at T=0 hours (when the reactants were first added), T=1 hour and T=4 hours. A spectrum of the benzaldehyde used for this reaction was also included.

Discussion

The NMR analysis indicated that there was no peak around 10ppm present at T=0 hours to indicate the presence of benzaldehyde, but that peak was present at T=1 hours (10.03 ppm). The peak was not present at T=4 hours. The acetone peak at 2.5ppm was present in T=0 hours and T=1 hour, but greatly reduced in the T=4 hour spectrum. The doublet present in the T=4 hours spectrum at 7.1 ppm indicate that a small amount of dibenzalacetone formed.

Conclusion

No trans-dibenzalacetone was produced. Product was successfully obtained in EXP284.

Log

2012-07-16

11:56 Added 20 mL of ethanol to a 50 mL Erlenmeyer flask.
12:02 Added 5.1245 g of piperidine to the flask and placed on stir plate.
12:11 Added 0.8639 g of acetone to a 5-dram snap cap vial.
12:14 Added 3.1393 g of benzaldehyde to the 5-dram vail.
12:18 Added contents of 5-dram vial with acetone and benzaldehyde to the 50 mL flask drop-wise as the solution was stirring. Removed a few drops of the reaction mixture and added to inner coaxial NMR Tube 1. Applied heat to the reaction mixture to reflux.
12:50 Placed Tube 1 in a thin-walled NMR tube holding CDCl3 and analyzed the sample by 500 MHz HNMR. The file of the spectrum was saved as UCEXP283_t0 (reaction time = 0 hours).
13:20 Reaction mixture obtained more of a yellow color. A few drops of the reaction mixture was removed and placed in inner coaxial HNMR Tube 2.
13:24 A few drops of benzaldehyde was added to inner coaxial HNMR Tube 3.
13:46 NMR Tubes 2 and 3 were analyzed by 500MHz HNMR and the files were saved as UCEXP283_t1 (reaction time = 1 hour) and UCEXP283_benzaldehyde.
16:57 A few drops of the reaction mixture was removed from the yellow solution. No crystals were visible. The few drops were added to inner coaxial NMR Tube 4. Tube 4 was placed in a thin-walled NMR tube containing CDCl3 and the sample was analyzed by 500MHz HNMR. The file of the spectrum was saved as UCEXP283_t4 (reaction time = 4 hours). The flask was removed from the hot plate and allowed to cool to room temperature.

2012-07-17

9:35 No crystals were visible in the solution. The solution was a yellow color. Placed the solution on ice.
11:00 No crystals formed from the solution.