Researcher

Matthew McBride

Objective

To determine the recrystallization yield of trans-dibenzalacetone (Product 284A from UCEXP284) from ethanol

Procedure

Approximately 0.8 g of trans-dibenzalacetone was added to a 10 mL Erlenmeyer flask. Ethanol was added to this flask and the solution was placed on the hot plate to boil. Once the solution was boiling, drops of ethanol were added to the flask until all of the crystals had entered the solution. The flask was placed in a 25°C water bath to cool to room temperature. The crystals were filtered and dried.

Results

Characterization of Product 321A
Amount: 0.6402 g
Recrystallization Yield: 77%
Appearance: Yellow crystals
HNMR Spectrum
Purity: Pure sample with a small amount of ethanol remaining

Calculation Sheet

Discussion

Using the temperature curve, the solubility of dibenzalacetone in ethanol at the boiling point is predicted to be around 1.27M. The experimentally measured solubility at boiling point was 1.23M.

Based on the temperature curve, the predicted recrystallization yield is 92% and the experimentally measured boiling point of 1.23M also supports this predicted yield. However, the actual yield for this experiment was 77%. During the transfer of the crystals from the filter paper to the vial, some of the crystals were likely lost and contributed to the lower yield.

Conclusion

Trans-dibenzalacetone was recrystallized from ethanol in a 77% yield and the solubility at boiling was measured to be 1.23M.

Log

2012-07-19

11:49 The weight of the empty 10 mL Erlenmeyer flask with a cap was 19.3285 g.
11:56 Trans-dibenzalacetone (Product 284A from UCEXP284 was added to the flask and the flask then weighed 20.1643 g. This means 0.8358 g of trans-dibenzalacetone was added to the flask.
12:00 Approximately 2 mL of ethanol was added to the flask and the flask was placed on the hot plate to heat.
12:11 The solution was boiling, but a few crystals were still visible in the solution so a few drops of ethanol were added.
12:12 All of the crystals were observed to have entered the boiling solution. The flask was removed from the heat.
12:15 The weight of the flask with the cap, dibenzalacetone and ethanol was 22.0827 g. This means 1.9184 g of ethanol was added to the flask.
12:23 The flask was sealed with parafilm and it then weighed 22.3479 g. The flask was placed in a 25°C water bath.
14:55 The flask was removed from the water bath.
14:56 The weight of the flask with the cap, content and parafilm was 22.3498.
15:09 The solution was filtered on the Buchner funnel using suction filtration. The yellow crystals were captured on the filter paper. The crystals were spread across the filter paper over the suction to allow the crystals to dry. These crystals were Product 321A.
15:52 The weight of the 5-dram vial empty (no cap) was 11.9494 g.
15:57 The weight of the 5-dram vial with the recrystallized product was 12.5896 g. There was 0.6402 g of recovered product.
16:19 0.0692 g of Product 321A was added to a 5-dram snap cap vial and then 0.4 mL of CDCl3 was added to the vial. The crystals dissolved into solution immediately. The solution was transferred to NMR Tube 1 and analyzed by 500MHz HNMR. The file of the spectrum was saved as ONSEXP321_A.