Researcher

Valentine Anyiam

Objective

Determination of the solubility of benzoic acid in ethylene glycol, diethylene glycol and glyme.

Procedure

Obtain three different test tubes and fill each one with about 350-360mg of benzoic acid. Mix 1mL of ethylene glycol within the first test tube, 1mL of diethylene glycol within the second test tube and 1mL of glyme within the third test tube. Seal the solutions and then place each of them within a water bath to boil until the solid dissovles, but do not allow the temperature of the water bath to exceed the boiling point of the solvents (Note: the glycol solutions boil at close to 200C and glyme boils at close to 80C). After the solutions have dissolved, place the samples within a water bath at room temperature until a precipitate forms (it may take longer for some of the solutions to precipitate out due to super saturation).

Results

Solubility Sheet 1
The concentrations of benzoic acid dissolved in ethylene glycol and diethylene glycol were determined to be 2.04M and 2.054M respectively from the first NMR analysis in CDCl3 solvent. The second NMR analysis of benzoic acid in ethylene glycol with CDCl3 solvent was determined to be 2.786M. All values obtained via NMR with CDCl3 solvent were deemed unusable, after noticing that the ethylene glycol solution was not completely miscible in CDCl3 solvent. An NMR analysis was later obtained for both glycol solutions using MD4 solvent instead. The concentrations of benzoic acid in ethylene glycol and diethylene glycol were determined to be 1.84M and 1.03M respectively in MD4 solvent. Not enough time was available to finish the preparation of benzoic acid in glyme, therefore the concentration of benzoic acid in glyme has not been determined.
Exp284Pic1Trial2.jpg
Pic1: Samples A, B and C after being heated and cooled in a room temperature bath. Each sample contained roughly 250mg of benzoic acid. No precipitate in any of the samples.


Exp284Pic2A2S.jpg
Pic2: Samples A2 and B2 after being heated in and cooled in room temperature water bath. Each sample had about 360mg of benzoic acid. Only sample A2 showed signs of precipitation.


Exp284Pic3B2S.jpg
Pic3: Sample B2 after sitting within the room temperature water bath for over an hour. Precipitation is now present.


Exp284Pic4C2.jpg
Pic4: Sample C2 after initial preparation of about 360mg of benzoic acid in 1mL of solvent.


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Pic5: Picture of the saturated solutions of benzoic acid in ethylene (left) and diethylene (right) glycols before taking the final NMR measurements of them.

Discussion

A couple minutes after the solution of benzoic in ethylene glycol was placed within the room temperature bath, the solution immediately precipitated and an NMR analysis of the sample, with CDCl3 solvent, revealed the solubility to be 2.04M at 23C. About an hour after the solution of benzoic acid in diethylene glycol was placed within the room temperature bath, the solution started to show signs of precipitation and an NMR analysis of the sample, with CDCl3 solvent, revealed the solubility to be 2.054M at 21C. Within the hour gap, the room temperature water bath had decreased from 23C to 21C. It is possible that the glycol solutions may be super saturated so an NMR analysis of the two samples was performed again a couple days later. After obtaining an NMR spectrum of the ethylene glycol solution again, the solubility was revealed to be 2.786M which indicates a problem with the sample. Further observation of the NMR sample for the ethylene glycol solution showed that it had formed a subtle yet separate layer on top. Because of this an NMR analysis of the two solutions was performed again, but this time using MD4 solvent instead of CDCl3. The NMR analysis was performed a couple days later, and before doing so, the solutions seemed to have precipitated even more than last time. An NMR analysis of the solutions with MD4 revealed the solubility of benzoic within ethylene and diethylene glycol at 20C to be 1.028M and 1.84M, respectively. The results for benzoic acid in ethylene glycol compares slightly with values published online, which gives a solubility of 0.7M at 18C and 1.5M at 25C. It does not however match up with the predicted values, for benzoic acid in ethylene glycol, which gives a value of 2.62M.

Conclusion

The solubility of benzoic acid in ethylene glycol was determined to be 1.028M at 20C. The solubility of benzoic acid in diethylene glycol was determined to be 1.84M at 20C. These values were obtained in methanol-D4. Any previous values of ethylene glycol or ethylene glycol polymers diluted in CDCl3 cannot be used because the solvents are not miscible.

Log

2012-04-25

13:15- 0.1227g of benzoic acid was poured into a 20mL test tube labeled test tube (A).
13:17- 0.1228g of benzoic acid was poured into a 20mL test tube labeled test tube (B).
13:19- 0.1226g of benzoic acid was poured into a 20mL test tube labeled test tube (C).
13:23- 1mL of ethylene glycol was mixed with the benzoic acid in test tube A.
13:26- 1mL of diethylene glycol was mixed with the benzoic acid in test tube B.
13:29- 1mL of glyme was mixed with the benzoic acid in test tube C.
13:35- A beaker was filled about 1/3 of the way with water and then placed on top of a hot plate to heat. The hot plate was turned to a setting of about 9.
13:39- The temperature of the water bath reached 93C. The setting of the hot plate was then turned down to about 3. Test tubes A and B were sealed with parafilm and then placed into the water bath.
13:41- Another water bath was prepared with warm water to be set at room temperature. The temperature of this water bath is at 30C. A little bit of cold tap water was poured into the this water bath.
13:45- No solid was seen within the solution in test tube C. The glyme solvent seemed to have dissovled the benzoic acid completely and so more benzoic acid (0.134g) was added into the solution in test tube C.
13:48- Temperature of the heating water bath is at 90C. The hot plate was turned off and test tubes A and B were taken out of the heated water bath and placed into the water bath set to room temperature. The temperature of this water bath is at 28C. A little more cold water was poured into this beaker.
13:49- Test tube C was then sealed with parafilm and then suspended within the water bath on top of the hot plate for about 1-2min.
13:51- The temperature of the water bath on top of the hot plate is at 86C. Test tube C was taken out of this water bath and then placed into the water bath set to room temperature. The temperature of this water is at 24C.
13:53- All three solutions were left within the room temperature water bath to be checked again later for presence of any precipitate within the solutions.
15:47- The room temperature water bath was at 18C. No precipitate had formed within any of the solutions. Pic1 was taken of all 3 solutions.
17:42- The hot plate was turned back on to a setting of about 8 to heat the water bath that was on top of it. The temperature of the room temperature water bath is at 18C.
17:43- 0.1318g of benzoic acid was added into test tube A.
17:46- Warm water was added to the room temperature water bath.
17:48- Room temperature water bath is at 27C.
17:51- 0.1323g of benzoic acid was added into test tube B. Room temperature water bath is at 26C.
17:54- The temperature of the water bath on top of the hot plate is now at 101C. The hot plate was turned off and test tubes A and B were placed into the hot bath.
17:57- Test tubes A and B were taken out of the water bath. The supernatant within test tube A was pipetted out and placed into another 20mL test tube which was then placed into the room temperature water bath. The room temperature water bath is at 24.5C. The supernatant within test tube B was also pipetted out and placed into another 20mL test tube which was also placed into the room temperature water bath.
18:02- The temperature of the water bath on top of the hot plate is at about 80C. Test tube C was placed back into this water bath to heat.
18:05- Test tube C was taken out the heated water bath and placed back into the room temperature water bath. Room temperature water bath is at 24C.

2012-04-26

10:37- Two clean 20mL test tubes were acquired to rerun the experiment.
10:41- 0.3655g of benzoic acid were added into a clean new test tube labeled test tube (A2)
10:42- A beaker nearly half filled with water was placed on top of a hot plate. The hot plate was turned on to a setting of 10. Current temperature is 21C.
10:44- 0.3642g of benzoic acid were added into a clean new test tube labeled test tube (B2)
10:48- 1mL of diethylene glycol was poured into test tube B2.
10:51- 1mL of ethylene glycol was poured into test tube A2.
10:52- Test tubes A2 and B2 were both covered on top with parafilm. The temperature of the boiling water reached 105C. The setting on the hot plate was turned down from 10 to 8. Test tubes A2 and B2 were placed into the boiling water bath.
10:58- A room temperature water bath was set up with the temperature at 26C.
11:02- The temperauture of the boiling water is still at 105C. The hot plate was turned off and test tubes A2 and B2 were taken out of the boiling water. The supernatant within test tube A2 was transferred into a clean new 20mL test tube labeled A2S while the supernatant within test tube B2 was transferred into another clean 20mL test tube labeled B2S. While transferring the supernatant within test tube A2 to test tube A2S, a piece of volumetric pipet broke off and was stuck within test tube A2S as shown in Pic2.
11:06- Test tubes A2S and B2S were placed into the room temperature water bath. The room temperature water bath is at 26C.
11:20- The room temperature water bath is now at 23C. The solution within test tube A2S precipitated out very well, whereas no precipitate was seen within the solution in test tube B2S.
11:23- Pic2 was taken of both test tubes.
11:45- About 100 microliters of just the liquid solution within test tube A2S was pipetted out and transferred into a small test tube containing about 800 microliters of CDCl3 solvent.
11:46- This solution was mixed together and transferred into an NMR tube labeled NMRA1EG. This tube was then taken downstairs for NMR analysis.
12:10- The NMR spectrum was captured for NMRA1EG, analyzed and then copied into a flash drive.
12:28- After heading back upstairs the sample B2S within the room temperature water bath was rechecked for signs of precipitation. The room temperature water bath is now at 21C and the solution within test tube B2S has also precipitated out.
12:30- Pic3 was taken of sample B2S.
12:39- About 100 microliters of just the liquid solution within test tube B2S was pipetted out and transferred into another small test tube containing about 800 microliters of CDCl3 solvent.
12:40- This solution was mixed together and transferred into an NMR tube labeled NMRB1DEG. This tube was then taken downstairs for NMR analysis.
12:52- The NMR spectrum was captured for NMRB1DEG, analyzed and then copied into a flash drive.

2012-04-27

10:13- 0.3611g of benzoic acid was added into a clean test tube labeled test tube C2
10:15- The room temperature water bath containing test tubes A2S and B2S is at a temperature of 19C. The solution within test tube B2S seems to have precipitated out a little more. Two pieces of parafilm were cut out and used to seal test tubes A2S and B2S.
10:25- 1mL of glyme solvent was poured into test tube C2. Test tube C2 was then sealed with a piece of parafilm.
10:27- One may not expect over 360mg of benzoic acid to take up such little space and so Pic4 was taken of the benzoic acid in glyme solution to show how only a small amount of benzoic acid can weigh up to 360mg.
13:20- The NMR spectrum for NMRB1DEG wasn't zeroed correctly.
13:25- The NMR spectrum for NMRB1DEG was reopened on the computer for NMR analysis, zeroed properly and recopied into a flash drive.
13:30- The spectrum for NMRA1EG was converted into a jdx file and uploaded onto the wiki.
13:31- The spectrum for NMRB1DEG was converted into a jdx file and uploaded onto the wiki.
13:50- A new solubility sheet was created for Exp284 and the data from the NMR spectrums of the two glycol solutions, were edited unto the solubility sheet.

2012-05-02

17:15- The NMR spectrum for benzoic acid in diethylene glycol, NMR2B2DEG, was obtained and saved within a flash drive.
17:20- The NMR spectrum for benzoic acid in ethylene glycol, NMR2bA2EG, was obtained and saved within a flash drive.
17:40- Emptied the NMR tubes containing samples NMR2bA2EG and NMR2B2DEG, washed the tubes with acetone and then air dried both of the NMR tubes.
17:45- The room temperature water bath containing the saturated solutions of benzoic acid in ethylene and diethylene glycol, samples A2S and B2S respectively, was at 20C.
17:46- A third NMR sample was prepared for sample A2S within an NMR tube. About 800 microliters of CDCl3 was mixed with about 100 microliters of just the liquid in the saturated solution of benzoic acid in ethylene glycol. This sample was labeled as NMR3A2EG.
17:48- A third NMR sample was prepared for sample B2S within an NMR tube. About 800 microliters of CDCl3 was mixed with about 200 microliters of just the liquid in the saturated solution of benzoic acid in diethylene glycol. This sample was labeled as NMR3B2DEG.
17:49- Pic5 was taken of samples A2S and B2S.
18:00- The NMR spectrum for sample NMR3B2DEG, was obtained and saved within a flash drive.
18:04- The NMR spectrum for sample NMR3A2EG, was obtained and saved within a flash drive.

2012-05-03

10:30- A fourth NMR sample was prepared for sample A2S within an NMR tube and was labeled as NMR4A2EG. This time the sample was prepared using the MD4 as the solvent instead of CDCl3.
10:33- A fourth NMR sample was prepared for sample B2S within an NMR tube and was labeled as NMR4B2DEG. This time the sample was prepared using the MD4 as the solvent instead of CDCl3.
10:55- The NMR spectrum for sample NMR4A2EG, was obtained and saved within a flash drive.
11:02- The NMR spectrum for sample NMR4B2DEG, was obtained and saved within a flash drive.
12:33- The NMR spectrums for samples NMR4A2EG and NMR4B2DEG were uploaded unto the wiki and then unto the solubility sheet 1.
14:00- A few more microliters of MD4 were added into the NMR tube containing NMR4A2EG. Another NMR spectrum was obtained for the sample because the one obtained before was not useable. This spectrum was saved as NMR5A2EG and was saved on a flash drive.
14:12- The NMR spectrum for sample NMR5A2EG was uploaded unto the wiki and then unto the solubility sheet 1.