Researcher

Valentine Anyiam

Objective

Determination of the solubility of benzoic acid in ethylene glycol and diethylene glycol by mixing the solutions with a magnetic stirrer.

Procedure

Prepare a 2M solution of benzoic acid in ethylene glycol and in diethylene glycol. Place a stir bar within the solutions and then place these solutions on top of a magnetic stir bar to spin for over a day. Check the next to see if the solutions had dissolved. If they have they take an NMR sample of the solution. If not, then add a little more benzoic acid to the solution and allow it to spin again over a day (make sure to note how much benzoic acid is added if need be).

Results

Solubility Sheet 1
Exp294pic1.jpg
Pic1: Benzoic acid in ethylene and diethylene glycol after being stirred continously for 3 days.

Discussion

NMR analysis of benzoic acid in ethylene glycol within a double NMR tube and with CDCl3 solvent, revealed the concentration to be 0.53M at 23C. NMR analysis of benzoic acid in ethylene glycol dissolved in MD4 solvent revealed the concentration to be 0.56M at 23C. This result is very similar to the result obtained with CDCl3 solvent which shows that the results are reproducible. These results however, do not match up well with the results published online, which gives a value of 0.7M at 18C and 1.5M at 25C. NMR analysis of benzoic acid in diethylene glycol using CDCl3 solvent revealed the concentration to be 1.86M at 23C. This implies that the trend in solubility of benzoic acid in glycol solvents goes up instead of going down which contradicts the initial predictions for the solubility of benzoic acid.

Conclusion

The solubility of benzoic acid in ethylene glycol was determined to be about 0.5M at 23C. The solubility of benzoic acid in diethylene glycol was determined to be about 1.9M at 23C. The special NMR tube with a double chamber has also been shown to be a viable tool for NMR analysis with CDCl3 solvent. (Due to new information obtained from EXP295, the result obtained for the solubility of of benzoic acid ethylene glycol is most likely false).

Log

2012-05-18

14:39- 0.4531g of benzoic acid was placed into a small vial labeled EG.
14:46- 0.4479g of benzoic acid was placed into a small vial labeled DEG.
14:55- 2mL of ethylene glycol was poured into vial EG.
15:02- 2mL of diethylene glycol was poured into vial DEG.
15:03- Stir bars were placed within each vial. The vials were then placed on top of a magnetic stirrer. The magnetic stirrer was turned on and set to 150rpm.

2012-05-21

13:10- The magnetic stirrer was turned off. The solid within vial DEG had completely dissolved, whereas the solution within vial EG seems to have become very soapy.
13:12- Pic1 was taken of the two solutions.
14:46- 0.1527g of benzoic acid was added to vial DEG.
14:48- Vial DEG was sealed with parafilm covering and put back on top of the magnetic stirrer with the stir bar inside of it. The magnetic stirrer was turned on and once again set to 150rpm.
14:50- Vial EG was sealed with parafilm covering and was left to sit, to see if the solution would settle down.

2012-05-22

14:15- The magnetic stirrer was turned off. This time the extra benzoic acid that was added to vial DEG did not completely dissolve after being continuously stirred over night.
14:18- The solution within vial EG did not settle much and still had somewhat of a soapy appearance.
14:28- The liquid solution within vial EG was transferred into a small suction flask via vacuum filtration. Not enough CDCl3 solvent was available to use to prepare NMR samples with.

2012-05-23

13:49- About 300 microliters of the ethylene glycol solution within vial EG was pipetted into the inner chamber of the special NMR tube.
14:11- A little less than 1mL of CDCl3 was transferred into the outer chamber of the special NMR tube.
14:37- An NMR spectra was obtained for the ethylene glycol sample and was saved as ONSCExp294NMRA1.
15:26- The remainder of the ethylene glycol solution within the suction flask was poured into a clean vial and was labeled vial EG2.
15:33- The liquid solution within vial DEG was transferred into a small suction flask via vacuum filtration.
15:35- This diethylene glycol solution was then poured into another clean vial and was then labeled vial DEG2.
15:46- Another NMR sample was prepared for the ethylene glycol solution, this time using MD4 solvent.
16:42- An NMR spectra was obtained for the ethylene glycol solution in MD4 and was saved as ONSCExp294NMRA1MD4.

2012-05-24

13:24- An NMR sample for the diethylene glycol solution was made within the special NMR tube using CDCl3 solvent.
13:44- An NMR spectra for this sample was obtained and was saved as NMRDEG1.