Researcher

Matthew McBride

Objective

To recrystallize the trans-dibenzalacetone from EXP279 in ethyl acetate to calculate the percent recovered.

Procedure

The trans-dibenzalacetone was weighed out and placed in a 10 mL Erlenmeyer flask. This flask was massed and 2 mL of ethyl acetate was added to the flask. The solution was heated on the hot plate to a boil to allow all of the crystals to dissolve into the solution. The flask was removed from the hot plate and allowed to cool at room temperature for 30 minutes. The crystals were recovered by filtration and massed.

Results

No value was obtained for the recrystallization from ethyl acetate.

HNMR spectrum of Product A - trans-dibenzalacetone following from recrystallization from ethanol.

Discussion

Ethyl acetate will not dissolve in water so is not as useful a solvent for recrystallization. The trans-dibenzalacetone crystals were wet with water since the ethyl acetate had not removed the water when the crude product was first recrystallized. This presence of water did not allow the recrystallization to take place.

The recrystallization from ethanol gave 0.3674 g trans-dibenzalacetone that had little impurities present as determined by NMR. The characteristic doublets of trans-dibenzalacetone were located at 7.7-7.8 ppm and 7-7.15 ppm. A singlet from water in the CDCl3 can be found at 1.6 ppm. There is an unidentified triplet at 1.2-1.3 ppm. This triplet is likely from the ethanol and the integration of this triplet is approximately 0.01. This small integration value indicates that very little ethanol was remaining on the crystals.

Conclusion

The percent recovery of trans-dibenzalacetone from ethyl acetate was not determined. However, 0.3674 g of the trans-dibenzalacetone was obtained that had the water removed following recrystallization from ethanol.

Log

2012-06-26

12:14 Added 0.7450 g of trans-dibenzalacetone to a 10 mL Erlenmeyer flask.
12:17 The weight of the flask with the crystals a cap was measured to be 19.3292 g. Picture #1 was taken.
12:31 The filter [[#|paper]] was weighed to be 0.1848 g.
12:33 Added 2 mL of ethyl acetate to the flask, swirled and placed the flask on the hot plate to boil. Hot plate was set to 105°C.
12:39 Increased the hot plate to 155°C.
12:43 The solution was boiling and all the crystals were dissolved. No additional ethyl acetate needed to be added because all of the crystals entered the solution.
12:44 The weight of the flask with the cap and solution after being removed from the hot plate as it was boiling was 20.8864 g. The flask was allowed to cool at room temperature (lab temperature was 22°C) fro 30 minutes. A small bubble formed by water from the crystals was observed to have formed.
13:28 Picture #2 was taken. The crystals did not come out of solution. Too much water was present. In order to recover the crystals, all the crystals were recrystallized from ethanol. 3 mL of ethanol was added to the remaining trans-dibenzalacetone crystals in the vial (approximately 0.7 g).
13:33 All of the solutions containing trans-dibenzalacetone were added to a 25 mL Erlenmeyer flask using ethanol to transfer. The flask was placed on the hot plate to boil in order to have all of the crystals enter the ethanol solution.
13:48 Solution was not boiling yet, but almost all of the crystals had entered the solution.
13:54 The solution was not boiling yet, but all of the crystals had entered the solution. The flask was removed from the hot plate and allowed to cool at room temperature.
14:16 No crystals visible in the solution yet. The flask was placed on ice.
14:24 The weight of an empty 5-dram vial (no cap) was 11.7788 g.
14:35 The flask was removed from the ice bath and filtered using a Buchner Funnel and suction filtration. The crystals were dried over the filter paper using the suction.
15:38 The crystals were removed from the filter paper and placed in the 5-dram vial. Picture #3 was taken.
15:43 The weight of the vial with the recovered trans-dibenzalacetone (Product A) was 12.1462 g. This is a recovery of 0.3674 g of Product A.

2012-06-27

10:24 0.0275 g of the trans-dibenzalacetone crystals were added to a 1-dram vial.
10:35 0.5 mL of CDCl3 was added to the vial and the contant was added to NMR Tube A.
10:38 The solution was analyzed by 500MHz HNMR.