Researchers

Rida Atif and Matthew McBride

Objective

To measure the room temperature solubility of benzoic acid in ethanol/water mixtures of 40:60, 50:50, 60:40 volumes as well as pure ethanol, and trans-dibenzalacetone in pure ethanol.

Procedure

Five 1-dram vials were filled with trans-dibenzalacetone or benzoic acid along with appropriate amounts of ethanol or ethanol/water mixtures. The vials were attached to an apparatus that would shake the vials while keeping them in a 25C water bath. The shake plate was turned on and the vials were allowed to shake for 15 minutes. After 15 minutes, the vials were removed and the supernatant from each of the vials was taken and put into inner coaxial NMR tubes; an NMR was taken of each of the samples. The vials were re-attached to the apparatus and allowed to shake for 45 more minutes (a total of 75 minutes). Again, the vials were removed and the supernatant from each vial was placed into inner coaxial NMR tubes, and spectrums were taken of each sample. The vials were once more attached to the apparatus and allowed to shake for the weekend (a total of 3 days). After 3 days, the vials were removed. The supernatant from each vial was transferred to inner coaxial NMR tube, and a spectrum was taken.

Results

SAMS Sheet 1 for dibenzylacetone in ethanol: Vial A - solubility at 25°C
15 minutes: 0.081M
75 minutes: 0.071M
3 days: 0.086M

SAMS Sheet 2 for benzoic acid in ethanol: Vial B - solubility at 25C
15 minutes: 2.67M - NMR has slight peak distortion
75 minutes: 2.529M - NMR has slight peak distortion and baseline issues
3 days: 2.674M - NMR has very slight peak distortion and baseline issues

SAMS Sheet 3 for benzoic acid in ethanol/water mixture 40:60 (vol): Vial C - solubility at 25C
15 minutes: 0.404M - NMR has slight baseline issues
75 minutes: 0.3848M - NMR has slight phasing issue and some peak distortions
3 days: 0.4812M - NMR has slight baseline issues and peak distortions

SAMS Sheet 4 for benzoic acid in ethanol/water mixture 50:50 (vol): Vial D - solubility at 25C
15 minutes: 0.813M - NMR has peak distortion
75 minutes: 0.8295M - NMR spectra has distorted peaks
3 days: 0.879M - NMR spectra has slight phasing and baseline issues as well as peak distortion

SAMS Sheet 5 for benzoic acid in ethanol/water mixture 60:40 (vol): Vial E - solubility at 25C
15 minutes: 1.311M - NMR has slight peak distortion
75 minutes: 1.299M - NMR has very small phasing issue
3 days: 1.2906M - NMR has very slight baseline issue

Discussion

Vial A:
Vial B: According to reported values, the average room temperature solubility of benzoic acid in ethanol is 2.614M. This value is very close to the one determined in this experiment.
According to Pal89, the solubility at room temperature should be about 2.75M, but this is not too far off from the experimentally determined value
Vial C: According to reported values, the average room temperature solubility of benzoic acid in ethanol/water (40:60) volume is 0.48M. This value is very close to the one determined in this experiment of 0.52M. According to Pal89 and Halford33 the solubility at room temperature for this solution is 0.3953M and 0.605M respectively. The value calculated in this experiment is roughly in the middle of the two values from literature. The 3 day value is higher than the ones determined beforehand, and since the second measurement was slightly lower than the first it is believed that the solution was saturated right after 15 minutes; in which case, if the first value is used then the solvent selector predicted higher whereas the Pal89 [[#|paper]] was right on point.
Vial D: According to reported values, the average room temperature solubility of benzoic acid in ethanol/water (50:50) volume is 0.78M while the last solubility determined in this experiment is about 0.88M, and that is slightly higher. According to Pal89, the room temperature solubility of this solution should be about 0.78M and that was observed around the 15 minute mark. The concentration of this solution increased with every measurement so it is difficult to say if the 3 day measurement was completely saturated. It would have helped to have taken another measurement the next day.
Vial E: According to reported values, the average room temperature solubility is 1.45M. This value is slightly higher than the solubilities determined in this experiment and in
Pal89which are both around 1.3M.

Conclusion

Vial A: The solubility of trans-dibenzalacetone in ethanol is 0.086M at 25°C
In general, the solvent selector is predicting slightly higher room temperature solubilities than the ones determined in this experiment as well as Pal89.
The results of Vial D should not be used because it is unclear whether or not the solution was saturated after 3 days, so the value given may not be a true value.

Log

2012-07-20

12:50 - The ethanol/water (40:60) volume created for use in EXP320 will be used in this experiment
12:59 - An ethanol/water (50:50) volume solution was created by combing 1.95g of ethanol and 2.5g of water (this was calculated based on each solvent's density)
1:10 - An ethanol/water (60:40) volume solution was created by combining 2.34g of ethanol and 2g of water (this was calculated based on each solvent's density)
1:29 - Vial A: 0.1398g trans-dibenzalacetone (Product 284A from UCEXP284 was added
1:31 - Vial B: 0.1177g benzoic acid
1:33 - Vial C: 0.1234g benzoic acid
1:36 - Vial D: 0.0930g benzoic acid
1:40 - Vial E: 0.1107g benzoic acid
1:54 - Vial A: a little over 1mL of pure ethanol was added
1:57 - Vial B: 0.33mL ethanol was added
1:59 - Vial C: 1.02mL ethanol/water (40:60) volume was added
2:01 - Vial D: 0.78mL ethanol/water (50:50) volume was added
2:03 - Vial E: 0.45mL ethanol/water (60:40) volume was added
2:05 - Each of the vials were covered in parafilm and attached to apparatus that was to be submerged in 25C water bath
2:08 - The shake plate was turned on to setting 2
2:23 - The shake plate was turned off
2:25 - Crystals were visible in each of the vials
2:30 - The supernatant from each of the vials (A-E) was transferred to the inner coaxial NMR tubes (1-5), respectively
2:33 - The vials were attached to the apparatus again
2:34 - The shake plate was turned on again
3:34 - The shake plate was turned off.
3:50 - The supernatants from each of the vials (A-E) was transferred into inner coaxial NMR tubes (1-5) respectively
4:00 - The vials were attached to the apparatus again.
4:02 - The shake plate was turned on again

2012-07-23

10:24 Vials were removed from the Shake Flask apparatus. Crystals were clearly visible in all of the vials, except for Vial D. In Vial D, only a few very small crystals were visible. The supernatant from each vial (A-E) was transferred into inner coaxial NMR tubes and analyzed by 500MHz HNMR.