Researcher

Valentine Anyiam

Objective

Determination of the solubility of benzoic acid in a series of glycol solvents: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and polyethylene glycol (PEG-400, average of 9 EG units) utilizing the shake flask method. The experiment would be carried out similar to the method published online by Beerbower, and with the use of a vortex genie.

Procedure

Prepare about a 1.5M solution of benzoic acid in ethylene glycol, and a 2M solution of benzoic acid within diethylene glycol, triethylene glycol, tetraethylene glycol and polyethylene glycol (make sure to measure the exact mass of both the solute and the solvents). All five solutions must then be placed on top of vortexer to shake for about a day. Check the next day to see if the solution have dissolved. If they have not, then prepare an NMR sample out of them for NMR analysis. If they have, then add some more benzoic acid to each of the solutions that had dissolved completely and allow those solutions to stir vigorously again for another day.

Results

Solubility Sheet 1
Exp295pic1.jpg
Pic1: glycol solutions after mixing for about a day, have completely dissolved
Exp295pic2.jpg
Pic2: more benzoic acid was added to solutions to create a 3M conc.
Exp295pic3.jpg
Pic3: glycol solutions after shaking on top of the vortexer for at least 2 days
Exp295pic4.jpg
Pic4: glycol solutions after being added with more benzoic acid. Vial DEG seems to be precipitating.

IMG_20120531_103257.jpg
Pic5: Glycol solutions with benzoic acid after shaking. Now all of the solutuions seem to be precipitating out.

Discussion

After preparing the initial concentrations of the solutions on 05-24 and allowing them to stir for about a day, all of the solutions had dissolved completely after checking them the next day. The temperature of the lab was at 23C before and after it was shaking on top of the vortex genie. The concentrations that were initially prepared was about 1.5M of benzoic in ethylene glycol and about 2M of benzoic acid in the other glycol solvents. This implies that the results gathered from EXP294, for the solubility of benzoic acid in ethylene glycol, were incorrect (the solubilty of benzoic acid in ethylene glycol was determined to be about 0.5M at 25C in that experiment). It also implies that the results published online may be incorrect as well. The values online show the solubility of benzoic acid in ethylene glycol to be 0.7M at 18C and 1.5M at 25C. An NMR analysis of the ethylene glycol solution revealed the concentration of benzoic acid in ethylene glycol to be 1.12M at 23C. A second NMR analysis of benzoic acid in ethylene glycol revealed the concentration to be 1.17M at 23C. This confirms that the solution was not super saturated. Within the NMR spectrum for benzoic acid in diethylene glycol there seemed to be traces of triethylene glycol impurity within the NMR spectrum. There was also the presence of two extra small peaks within the NMR spectrum of the diethylene glycol solution which weren't present within any other of the NMR spectuems for the other glycol solutions. These extra peaks were located at about the 8-9ppm range. An NMR analysis of the diethylene, triethylene, tetraethylene and polyethylene glycol solutions revealed the concentration of benzoic acid to be 2.2M, 2.5M, 2.6M and 2.4M respectively at 23C. This contradicts the trend predicted from the Abraham Descriptor model for benzoic acid in glycol solvents. Within the model, it was predicted that the benzoic acid was most soluble within ethylene glycol with the solubility decreasing as the number of carbon units increased until it leveled off and stayed rather constant after triethylene glycol. The recent result for the solubility of benzoic acid within polyethylene glycol also contradicts the results published online which states the solubility of benzoic acid in polethylene glycol to be 1.6M at 25C.

Conclusion

The solubility of benzoic acid in ethylene, diethylene, triethylene, tetraethylene and polyethylene glycol was determined to be about 1.15M, 2.2M, 2.5M, 2.6M and 2.4M respectively at 23C.

Log

2012-05-24

15:16- 0.3648g of benzoic acid was added into a small vial labeled EG.
15:18- 0.5190g of benzoic acid was added into a small vial labeled DEG.
15:20- 0.4763g of benzoic acid was added into a small vial labeled TEG.
15:21- 0.4730g of benzoic acid was added into a small vial labeled TetraEG.
15:23- 0.4756g of benzoic acid was added into a small vial labeled PEG.
15:36- About 2.509g of ethylene glycol was added to vial EG. Vial EG was then sealed with a screw cap.
15:41- About 2.466g of diethylene glycol was added to vial DEG. Vial DEG was then sealed with a screw cap.
15:44- About 2.391g of triethylene glycol was added to vial TEG. Vial TEG was then sealed with a screw cap.
15:47- About 2.404g of tetraethylene glycol was added to vial TetraEG. Vial TetraEG was then sealed with a screw cap.
15:51- About 2.315g of polyethylene glycol was added to vial PEG. Vial PEG was then sealed with a screw cap.
16:01- Parafilm was used to further seal all five of the vials and then these vials were duck taped on top of a vortex genie which was set to shake at a setting of 2. The temperature of the lab is at 23C.

2012-05-25

12:30- The vortex genie was turned off.
12:34- The duck tape was removed and the solutions were removed from the vortex genie. In all five solutions, the solid seems to have dissolved completely. The temperature of the lab is at 23C.
12:43- Pic1 was taken of all five solutions.
13:11- 0.3644g of benzoic acid was added to vial EG.
13:14- 0.2093g of benzoic acid was added to vial DEG.
13:15- 0.2487g of benzoic acid was added to vial TEG.
13:17- 0.2482g of benzoic acid was added to vial TetraEG.
13:19- 0.2435g of benzoic acid was added to vial PEG.
13:22- Pic2 was taken of all five solutions.
15:01- All five of the vials were covered with screw caps and resealed with parafilm covering.
15:05- The vials were then duck taped once again on top of a vortex genie along with five other vials containing solutions prepared by another person in the lab named Mark. The vortex genie was set to shake at a setting of 2.

2012-05-27

12:00- All of the solutions along with the duck tape, flew off the vortex genie. The solutions were placed back on top of the vortex genie with the duck tape to continue shaking.

2012-05-29

12:39- The vortex genie was turned off. All of the solutions dissolved completely except for the ethylene glycol solution. The metal part of the vortex genie also felt warm.
12:48- Pic3 was taken of all five solutions. The temperature of the lab is at 23C.
13:21- 0.2440g of benzoic acid was added to vial DEG.
13:23- 0.2422g of benzoic acid was added to vial TEG.
13:26- 0.2504g of benzoic acid was added to vial TetraEG.
13:28- 0.2422g of benzoic acid was added to vial PEG.
13:36- Pic4 was taken of all the glycol solutions except for the ethylene glycol solution. The solution within vial DEG appears to be precipitating out for some unknown reason.
13:41- The four glycol solutions were sealed with screw caps, covered with parafilm covering and duck taped back on top of the vortex genie. The vortex genie was set to shake at a setting of 2.

2012-05-30

9:55- The solutions flew off of the vortex genie while it was still shaking. All of the solid within the tetraethylene glycol solution seems to have dissolved almost completely. Only one tiny fragment of solid seems to still be present within the solution. More benzoic acid may need to be added.
10:15- The ethylene glycol solution was vacuum filtered into a suction flask. The solution within the suction flask was then transferred into a clean vial.
10:36- Some solid particles seems to have also gotten into the ethylene glycol solution within the vial. This solution was transferred again into another clean vial, this time using a glass pipet with a small piece of Kim Wipe paper within it as a filter.
10:55- An NMR sample was prepared with the ethylene glycol solution and CDCl3 solvent within the double NMR tube.
13:20- The ethylene glycol solution within the inner chamber of the double NMR tube seems to have precipitated out a little. However, the filtered solution with the vial had not precipitated out at all. This may not affect the results obtained from NMR.
13:29- An NMR analysis was taken for the ethylene glycol solution and was saved as ONSCExp295NMREG1.

2012-05-31

10:25- All of the solutions seem to be precipitating out for some unknown reason.
10:30- The remaining filtered ethylene glycol solution within the clean vial was poured back into vial EG. The ethylene glycol solution that was within the 2-chamber NMR tube was also poured back into vial EG.
13:47- The glycol solutions were duck taped on top of the vortex genie along with five other glycol solutions containing cinnamic acid. The vortex genie was set to shake at a setting of 2.

2012-06-01

10:04- The vortex genie was turned off. None of the solutions dissolved any further. Instead they all seem to be precipitating out.
10:10- Pic5 was taken of all five solutions.
10:25- A second NMR sample was prepared for the ethylene glycol solution in the double NMR tube with CDCl3 solvent.
10:39- An NMR analysis was taken for the ethylene glycol solution and was saved as ONSCExp295NMREG2.
13:51- An NMR sample was prepared for the diethylene glycol solution in the double NMR tube with CDCl3 solvent.
14:04- While attempting to an NMR analysis of the diethylene glycol solution, for some reason, it failed to lock for the sample. Another NMR sample will need to be prepared for this solution.
14:26- The diethylene glycol solution was transferred into a small, clean vial, through the use of a glass pipet with a small piece of Kim Wipe paper within it as a filter. This vial was covered with a small cap.
14:35- The triethylene glycol solution was transferred into a small, clean vial, through the use of a glass pipet with a small piece of Kim Wipe paper within it as a filter. This vial was covered with a small cap.
14:43- The tetraethylene glycol solution was transferred into a small, clean vial, through the use of a glass pipet with a small piece of Kim Wipe paper within it as a filter. This vial was covered with a small cap.
14:50- The polyethylene glycol solution was transferred into a small, clean vial, through the use of a glass pipet with a small piece of Kim Wipe paper within it as a filter. This vial was covered with a small cap.

2012-06-07

12:53- An NMR sample was prepared with the diethylene glycol solution in MD4 solvent.
12:54- An NMR sample was prepared with the triethylene glycol solution in MD4 solvent.
12:58- An NMR sample was prepared with the tetraethylene glycol solution in MD4 solvent.
13:01- An NMR sample was prepared with the polyethylene glycol solution in MD4 solvent.
16:09- The remaining benzoic acid solutions were placed back on top of the vortex genie along with glycol solutions containing cinnamic acid for EXP296. The vortex genie was set to shake at a setting of 2.
16:52- An NMR analysis was taken for the diethylene, triethylene, tetraethylene and polyethylene glycol solutions and were each saved as ONSCExp295NMRDEG1, ONSCExp295NMRTEG1, ONSCExp295NMRTetraEG1 and ONSCExp295NMRPEG1 respectively.

2012-06-08

14:05- The vortex genie was turned off.