Researcher

Rida Atif

Objective

To determine the room temperature solubility of benzoic acid (exp318a) in ethanol/water mixtures of 30:70, 40:60, and 50:50 volumes to [[#|confirm]] results of EXP323 using a temperature controlled bath set to 25C.

Procedure

Solutions of ethanol/water (30:70), (40:60), and (50:50) volumes were created. About 0.1g of benzoic acid was added into three 1-dram vials each. One of the solutions was also put into each of the vials to create a 1M solution. The three vials were attached to an apparatus to be suspended in a 25C water bath while being able to shake on the shake plate. The vials were allowed to shake for 15 minutes, and then a few drops of the supernatant from each vial was put into an inner coaxial NMR tube. NMR's were taken of each of the sample. The vials were allowed to shake for 60 minutes, 105 minutes, and 1 day with a small amount of the supernatant being extracted after every time interval. NMR's were taken of the samples after 60 minutes, 105 minutes, and 1 day as well.

Results

Vial A (30/70 ethanol/water)
SAMS Sheet 1
15 minutes - 0.1206M very slight peak distortions
60 minutes - 0.1299M very slight peak distortions and phasing issues
There was not enough supernatant in the vial to take NMR spectrums after 105 minutes

Vial B (40/60 ethanol/water)
SAMS Sheet 2
15 minutes - 0.5676M some peak distortions
60 minutes - 0.5288M slight peak distortions
105 minutes - 0.5548M very slight peak distortions
1 day - 0.5256M slight peak distortions and slight phasing problems

Vial C (50/50 ethanol/water)
SAMS Sheet 3
15 minutes - 0.642M
60 minutes - 0.6355M slight phasing and peak distortion problems
105 minutes - very bad spectrum
1 day - 0.6875M distorted peaks

Discussion

Vial A: There was not enough supernatant in the vial for an NMR to be taken for the 105 minutes onward. According to just the 15 minute and 60 minute values though, it seems like the supernatant was not saturated after 60 minutes and that the solubility could have possibly gone up between 60 minutes and 105 minutes. This solubility is being done again in EXP327. However, so far, the values are close to the 0.12M value determined in Pal89
Vial B: According to the four values obtained at different times, it seems like the supernatant was saturated after 15 minutes since the solubility determined at 60 minutes was slightly lower than the first. In EXP323, the solubility at room temperature was determined to 0.4M whereas the one determined here was 0.568M. The solubility determined in Pal89 was closer to 0.4M, so this value may be higher than the true.
Vial C: According to the 3 spectrums that were usable (exp326vialc-105minutes was not useful since the peaks were not distinguishable) it seemed as if the supernatant was saturated after 15 minutes since the solubility determined at 60 minutes was slightly lower than the one before.In EXP323 the solubility determined at room temperature was around 0.8M; in this experiment it is around 0.65M. According to Pal89, the solubility is around 0.77M which is closer to the value determined in exp323.
The peak distortion and slight phasing issues in some of the spectrum should not be dramatic enough to affect solubilities significantly.

Conclusion

Vial A: The solubility of benzoic acid in ethanol/water (30:70) volume should be determined again and with more solvent available so the supernatant does not deplete quickly
Vial B: The solubility determined in this experiment is 0.5676M
Vial C: the solubility determined in this experiment is 0.642M

Log

2012-07-26

11:20 - A solution of ethanol/water 30:70 volume was made my mixing 1.17g of ethanol and 3.5g of water (mass calculated based on each solvent's density)
11:29 - A solution of ethanol/water 40:60 volume was made my mixing 1.56g of ethanol and 3g of water
11:37 - A solution of ethanol/water 50:50 volume was made my mixing 1.95g of ethanol and 2.5g of water
11:40 - 0.095g of benzoic acid was added into Vial A, a 1-dram vial
11:44 - 0.100g of benzoic acid was added into Vial B
11:50 - 0.100g of benzoic acid was added into Vial C
12:01 - 0.745g of ethanol/water (30:70) volume was added into Vial A (this is equivalent to 0.7787mL of the solvent with a density of 0.958g/mL)
12:08 - 0.772g of ethanol/water (40:60) volume was added into Vial B (this is equivalent to 0.8197mL of the solvent with a density of 0.942g/mL)
12:16 - 0.7566g of ethanol/water (50:50) volume was added into Vial C (this is equivalent to 0.8197mL of the solvent with a density of 0.923g/mL)
12:25 - The 3 vials were attached to an apparatus that would submerge them in a 25C water (temp controlled bath) bath while simultaneously shaking them using the Vortex Genie
12:26 - The shake plate was turned on to setting 2.
12:41 - The shake plate was turned off and the vials were removed from the waterbath
12:49 - Each of the supernatants from the vials was placed into inner coaxial NMR tubes (A-B, respectively)
13:01 - The shake plate was turned on again
13:46 - The shake plate was turned off and the vials were removed from the water bath
13:50 - The supernatant from each flask was put into inner coaxial NMR tubes
13:51 - It was noticed that the temperature of the water bath was 27C so it was turned down to 25C
14:06 - The shake plate was turned on again
14:51 - The shake plate was turned off and the vials were removed from the water bath
15:00 - The supernatant from each of the vials was transferred to an inner coaxial NMR tube (NMR could not be taken of Vial A because there was not enough supernatant in vial)
15:08 - The shake plate was turned on again

2012-07-27

11:22 - The shake plate was turned off
11:30 - A few drops of the supernatant from vial B and C were taken (because there was no supernatant left in Vial A) and transferred to an inner coaxial NMR tube.
11:35 - EXP326VialB-1day and EXP326VialC-1day NMR's were taken.