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Researcher

Matthew McBride

Objective

To synthesize trans-dibenzalacetone using the procedure from EXP279 (using this teaching manuel) and purifying by recrystallization from ethanol.

Procedure

Potassium hydroxide pellets are dissolved into water and then ethanol is added in an equal amount to the water. The solution is cooled and then acetone is added to the solution as it is stirring. Benzaldehyde (1.1M in approximately 50 mL solution) is added to the solution in a 2:1 ratio to acetone. The crude product is recovered by filtration and recrystallized from ethanol. The following Reaction Preparation Sheet was used to complete the reaction.

Results

Characterization of 307A

Amount: 0.1965 g
Appearance: Yellow solid
HNMR Spectrum of Product A
Purity: Some impurity visible

Characterization of 307B

Amount: 2.2560 g
Appearance: Yellow solid
HNMR Spectrum of Product B
Purity: A small amount of impurity present

Characterization of 307C

appearance: A solid round chunk of dark orange color
HNMR Spectrum of Product C

Discussions

Product A was the initial 1.6 g of the crude product recrystallized from ethanol just to be sure crystals could be recovered before recrystallizing all of the crude product. 1.638 g of crude product was used and only 0.1965 g of the product was recovered from the recrystallization from ethanol. The spectrum is messy with some impurity present, but this could also be due to the small amount of produced used to take the NMR.

Product B was the remaining 14.876 g of crude product. 2.2560 g of Product B was recovered following recrystallization from ethanol. The spectrum is slightly messy and does not have a straight baseline from 7-8ppm. Overall, the HNMR spectrums of Product A and Product B are nearly identical.

Product C was a small, solid ball shaped chunk recovered from the recrystallization of Product B. The HNMR spectrum is only indicating that it contained trans-dibenzalacetone wet with ethanol. It is unsure why this chunk formed or what exactly it formed from.

Conclusion

Trans-dibenzalacetone was recovered from this synthesis in a total amount of 2.4525 g. This is a yield of 39% for the reaction followed by recrystallization from ethanol. A large quantity of the crystals were visible in the crude product, so it is believed that most of the product is lost during the recrystallization.

Log

2012-07-02

16:42 Added 4.193 g of potassium hydroxide pellets to a 125 mL Erlenmeyer flask.
16:44 Added 16 mL of distilled water to the flask and swirled for 30 seconds to dissolve the pellets.
16:47 Added 16 mL of ethanol, added a stir bar and placed on the stir plate to stir.
16:52 Removed the flask from the stir plate and placed on the ice bath to cool.
17:00 Removed the flask from the ice bath and added 2.5 mL of acetone to the flask while it was on the stir plate. Added 6.0 mL of benzaldehyde to the reaction mixture. The reaction mixture obtained a thick yellow color within 30 seconds.
17:05 The reaction mixture was very thick and the solution needed to be swirled with a spatula in addition to the stir bar.
17:17 The flask was removed from the stir plate and filtered using a Buchner funnel. Took Picture #1. The yellow crude product was allowed to dry on filter paper using the suction.
17:23 The weight of the empty 50 mL flask was 40.549 g.
17:25 The suction was removed from the filter flask and Buchner funnel. A small amount of the crude product was transfered to the 50 mL flask. The weight of the flask was then 42.187 for a total of 1.638 g of crude product.
17:28 5 mL of ethanol was added to the flask and it was placed on the hot plate to heat and stir.
17:35 An additional 2 mL of ethanol were added to the flask.
17:36 All of the crystals had entered the solution (solution was not quite boiling yet). Picture #2 was taken. The flask was removed from the hot plate and set to the side to cool to room temperature.
17:44 Some crystals were visible in the solution. The flask was placed in the ice bath to cool further.
18:07 The flask was removed from the ice bath and filtered using a Buchner funnel and suction filtration. Picture #3 was taken. The crystals on the filter paper (Product A) were yellow and spread across the filter paper using a spatula while suction was still applied to dry the crystals.
18:13 The weight of an empty 5-dram vial with a label and no cap was 11.8095 g.
18:17 The suction was removed from the filter flask and Buchner funnel. The crystals were transfered from the filter paper to the 5-dram vial. The weight of the vial was 12.0060 g. 0.1965 g of Product A was recovered.
18:21 The weight of an empty 125 mL flask was 64.600 g.
18:23 The remaining crude product was transfered from the Buchner funnel to the 125 mL flask. The crude product was very clumpy. Picture #4 was taken. A spatula was used an in attempt to break some of the clumps apart. The weight of the flask with the crude product was 79.476 g. That was 14.876 g of crude product.
18:30 A stir bar was added to the flask and 40 mL of ethanol. The flask was placed on the hot plate to heat and stir.
18:34 5 mL of ethanol was added to the flask. Crystals were still visible in the solution.
18:39 5 mL of ethanol was added to the flask. Crystals were still visible in the solution.
18:41 5 mL of ethanol was added to the flask. Crystals were still visible in the solution.
18:44 5 mL of ethanol was added to the flask. Crystals were still visible in the solution.
18:46 The crystals were dissolved in the solution. The solution turned a dark, violet color. The flask was removed from the hot plate and placed in the ice bath to cool.
19:15 The flask was removed from the ice bath and filtered using suction filtration and a Buchner funnel. A very hard chunk with a dark orange color was found in the center of the captured crystals. The solid chunk (Product C) was removed and placed in a 5-dram vial. Picture #5 was taken.
19:25 The weight of an empty 5-dram vial with a label was 11.9174 g.
19:27 Picture #6 was taken of the dried product on the filter paper. The recovered product (Product B) was a light yellow and transfered to the 5-dram glass vial.
19:33 The weight of the vial with Product B was 14.1734 g. 2.2560 g of Product B was recovered.
19:40 0.015 g of Product A was placed in Vial A.
19:42 0.0197 g of Product B was placed in Vial B.
19:45 0.2320 g of Product C was placed in Vial C.
19:47 Approximately 0.75 mL of CDCl3 was added into Vial A, the solution was mixed to dissolve the solid, and the solution was placed in NMR Tube A.
19:49 Approximately 0.75 mL of CDCl3 was added into Vial B, the solution was mixed to dissolve the solid, and the solution was placed in NMR Tube B.
19:52 Approximately 0.75 mL of CDCl3 was added into Vial C, the solution was mixed to dissolve the solid, and the solution was placed in NMR Tube C.
20:17 Products A, B and C were analyzed by 500MHz HNMR. A small amount of solid was visible in NMR tubes A and B. The NMR spectrum of Product A was saved as ONSEXP307ProductA_1. The NMR spectrum of Product B was saved as ONSEXP307ProductB_1. The NMR spectrum of Product C was saved as ONSEXP307ProductC_1.