Researcher

Matthew McBride

Objective

To determine the solubility of trans-dibenzalacetone in diethyl ether and acetone using SAMS HNMR and the Shake Plate method to dissolve.

Procedure

Approximately 0.1 g of the trans-dibenzalacetone crystals were placed in two 1-dram screw cap vials. Then about 0.5 mL of the solvent was added to each vial. The vials were sealed and secured on the shake plate for 72 hours to create a saturated solution. The supernatant was then analyzed by HNMR to calculate the solubility using SAMS HNMR. The vials were placed back on the shake plate and analyzed again after 96 hours to ensure the solution was saturated and no more crystals entered the solution.

Results

SAMS Sheet 1 - solubility in diethyl ether: Vial 1
72 hours: 0.498M at 24°C

SAMS Sheet 2 - solubility in acetone: Vial 2
72 hours: 0.368M at 24°C
96 hours: 0.395M at 24°C

Discussion

A second solubility could not be obtained for Vial 1 (solubility in diethyl ether), so it is not certain that a saturated solution had been obtained. However, there was a thick layer of yellow crystals at the bottom of the vial after 72 hours of mixing on the stir plate, so the solution was likely saturated. The solubility should be measured again to confirm. The experimental determined the solubility was 0.498M. The Solvent Selector for Dibenzalacetone lists predicted solubility values for Model003 and the Abraham Descriptors. Model003 predicted the solubility of dibenzalacetone in diethyl ether to be 0.429M and the Abraham Descriptors predicted solubility of 0.145M at room temperature. The Model003 provided a highly accurate prediction and the Abraham Descriptors provided a predictions that was slightly low.

The solubility was measured in acetone to be 0.395M at room temperature (24°C). There were so few crystals remaining in the vial when the supernatant was removed to be analyzed that there is some doubt as to whether the solution was saturated. This solubility should be measured again to confirm the value. In the Solvent Selector, Model003 predicted a solubility of 0.854M in acetone and the Abraham Descriptors predicted 0.655M. Both of the predictions are slightly high compared to the experimentally measured solubility of 0.395M.

Conclusion

The solubility of trans-dibenzalacetone was measured to be 0.498M in diethyl ether at 24°C and was accurately predicted by Model003. The solubility of trans-dibenzalacetone was measured to be 0.395M in acetone at 24°C and the prediction by Model003 was a little high.

Log

2012-07-06

14:35 Added 0.1196 g of trans-dibenzalacetone (Product B from EXP308) to Vial 1 - a 1-dram screw cap vial.
14:39 Added 0.1684 g of trans-dibenzalacetone (Product A from EXP308) to Vial 2 - a 1-dram screw cap vial.
14:44 Added approximately 0.5 mL of diethyl ether into Vial 1. The solution was swirled around and some of the crystals entered the solution, but crystals were still visible.
14:47 Added approximately 0.5 mL of acetone into Vial 2. Crystals were still visible in the solution.
15:26 Crystals were visible in both vials. Each vial was sealed with parafilm and secured in a vertical position on the shake plate. The shake plate was turned on.

2012-07-09

10:52 Removed Vial 1 and 2 from the shake plate. Crystals were visible in Vial 1, but not visible in Vial 2. The vials were placed on the lab counter to cool to room temperature (lab temperature is 24°C).
11:37 Crystals were visible in Vial 2.
15:50 Added a few drops of the supernatant from Vial 1 into 0.5 mL of CDCl3 in a 1-dram snap cap vial and the solution was transfered to NMR Tube 2.
15:55 Added a few drops of the supernatant from Vial 2 into 0.5 mL of CDCl3 in a 1-dram snap cap vial and the solution was transfered to NMR Tube 3.
15:57 Analyzed the two solutions by 500MHz HNMR. The files of the spectrums were saved as ONSEXP313Vial1_72hours and ONSEXP313Vial2_72hours.
16:32 Added a few drops of diethyl ether to Vial 1, because there was very little supernatant remaining. Lots of crystals were visible in the solution.
17:02 Vials 1 and 2 were sealed with parafilm and secured in a vertical position on the shake plate. The shake plate was turned on.

2012-07-10

9:21 Removed Vials 1 and 2 from the shake plate. The vials had fallen forward slightly on the shake plate. Crystals were visible in Vial 1, but no crystals were visible in Vial 2. The vials were placed on the lab counter to cool to room temperature (lab temperature was 24°C).
11:20 Crystals were visible in both vials.
13:16 No supernatant could be removed from Vial 1. The supernatant had escaped. The supernatant from Vial 2 was placed in the inner coaxial NMR Tube 1.
14:01 The sample from Vial 2 was analyzed by 500MHz HNMR and the file of the spectrum was saved as ONSEXP313Vial2_96hours.