dba scheme .png

Researcher

Matthew McBride

Objective

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

Procedure

Add piperidine to ethanol. Then in a separate flask mix benzaldehyde and acetone together in a 2:1 molar ratio. Add the benzaldehyde and acetone mixture to the ethanol solution in a drop-wise manner. Allow the solution to reflux until crystals form. The following Reaction Preparation Sheet was used to plan this synthesis.

Results

The NMR Spectrums demonstrate the content of the reaction mixture at T=0, 1, 18 and 24 hours. The spectrum of the piperidine used for this reaction is also included.

Discussion

No crystals were formed from this reaction. The presence of the piperidine was not visible in the HNMR spectrums until after an additional 2 mL were added at T=18 hours. This low concentration of piperidine could be the reason that no product formed.

At T=0, the benzaldehyde peak is visible at 10.4 ppm. And acetone peak appears to be at 2.54 ppm. Based on observing these peaks, there does not seem to be a 2:1 ratio of benzaldehyde to acetone, but closer to a 1.25:1 ratio. In the future, the exact amount of each reactant will be weighed out and recorded.

At T=24, the benzaldehyde peak had disappeared, but it was difficult to see whether any product had formed. If there was product present, it was very little.

Conclusion

This reaction was not successful in producing trans-dibenzalacetone.

Log

2012-07-12

15:49 Added 20 mL of ethanol to a 125 mL Erlenmeyer flask.
15:53 Added 1 mL of piperidine to the flask.
16:00 Added 1.5 mL of acetone and 4.0 mL of benzaldehyde to the flask and allowed the solution to stir on the stir plate.
16:05 The solution was clear with no crystals visible. A few drops of the solution was removed and added to the inner coaxial NMR Tube 1. A loose fitting cap was placed on the flask and the heat was turned on to reflux the reaction mixture.
16:16 The solution was still clear (no crystals), but had obtained a slight yellow color.
16:45 NMR Tube 1 was placed into a thin-walled NMR tube containing CDCl3. Then the sample in NMR Tube 1 was analyzed by 500MHz HNMR and the file of the spectrum was saved as UCEXP281_t0 (reaction mixture when all of the reactants were first added together).
16:54 The solution was still clear and without crystals, but the yellow coloring of the solution was a bit stronger. A few drops of the solution was removed and added to the inner coaxial NMR Tube 2.
17:05 NMR Tube 2 was placed into a thin-walled NMR tube containing CDCl3. Then the sample in NMR Tube 2 was analyzed by 500MHz HNMR and the file of the spectrum was saved as UCEXP281_t1 (reaction mixture after 1 hour).

2012-07-13

10:23 The refluxing reaction mixture was clear with no crystals visible, but had obtained a darker yellow color.
10:33 A few drops of the reaction mixture was removed and added to the inner coaxial NMR Tube 3.
10:38 A few drops of the piperidine used for this experiment was added to the inner coaxial NMR Tube 4.
11:04 The samples in NMR Tube 3 and NMR Tube 4 were placed in a thin-walled NMR tube containing CDCl3. Then the samples were analyzed by 500MHz HNMR and the files of the spectrums were saved as UCEXP281_t18 (reaction mixture after 18 hours) and UCEXP281_piperidine.
11:08 Added 2 mL of piperidine to the reaction mixture and kept it on the hot plate to stir and reflux.
16:19 No crystals visible in the reaction mixture. A few drops of the reaction mixture removed and placed in the inner coaxial NMR Tube 5. This Tube 5 was placed in a thin-walled NMR tube containing CDCl3 and analyzed by 500MHz HNMR. The file of the spectrum was saved as UCEXP281_t24 (reaction mixture after 24 hours).