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. This experiment will also use the SAMS technique with a 2-chamber NMR tube to avoid solubility problems between CDCl3 and ethylene glycol polymers [add relevant links JCB]

Procedure

Obtain five separate test tubes and fill each one with about 300mg of benzoic acid. Then mix 1mL of ethylene glycol within the first test tube, 1mL of diethylene glycol within the second test tube, 1mL of triethylene glycol within the third test tube, 1mL of tetraethylene glycol within the fourth test tube and 1mL of polyethylene glycol within the fifth test tube. Place each of these samples within a hot water bath to boil for several minutes or until the solid dissolves. Do not allow the temperature of the water bath to exceed the temperature of the solvents (Note: glycol solvents boil at around 200C). After boiling, if the solutions have dissolved completely, then you may transfer them within another water bath at room temperature. If the solutions have not dissolved completely, then transfer the supernatant within each solution into another clean test tube and then place these test tubes within the room temperature water bath. Allow them to sit within the water baths for approximately 1 day. Check the next day for signs of precipitation.

Results

Solubilities could not be obtained.

Discussion

None of the glycol solutions precipitated out after sitting in the room temperature water bath for a day. However, the water bath on top of the hot plate, may not have been boiling initially before the solutions were placed within them to boil. It is also possible that the solutions could be supersaturated.

Conclusion

The benzoic acid solutions may be too super saturated in order to confirm with accuracy the solubilities via NMR analysis.

Log

2012-05-07

10:40- 300.9mg of benzoic acid was weighed out and pour into a 20mL test tube labeled EG. The test tube was then covered with a screw cap.
10:43- 305.2mg of benzoic acid was weighed out and pour into a 20mL test tube labeled DEG. The test tube was then covered with a screw cap.
10:45- 305.4mg of benzoic acid was weighed out and pour into a 20mL test tube labeled TEG. The test tube was then covered with a screw cap.
10:48- 303.4mg of benzoic acid was weighed out and pour into a 20mL test tube labeled TetraEG. The test tube was then covered with a screw cap.
10:50- 305.3mg of benzoic acid was weighed out and pour into a 20mL test tube labeled PEG. The test tube was then covered with a screw cap.
16:14- A beaker was filled half way with water and placed on top of a hot plate to be used as the hot water bath. The hot plate was then turned on to a setting of 6.
16:16- About 1mL of polyethylene glycol was poured into test tube PEG.
16:19- About 1mL of tetraethylene glycol was poured into test tube TetraEG.
16:21- About 1mL of triethylene glycol was poured into test tube TEG.
16:24- About 1mL of diethylene glycol was poured into test tube DEG.
16:29- About 1mL of ethylene glycol was poured into test tube EG.
16:34- The hot plate was turned up to a setting of 9.
16:35- All five solutions were placed within the hot water bath.
16:37- Another water bath was prepared to be used as a room temperature water bath. The temperature of this water bath is at 26C.
16:45- The hot plate was turned off. None of the solutions dissovled completely.
16:47- The supernatant within test tube EG was pippeted into another clean 20mL test tube. This test tube was labeled EG-2 and was placed within the room temperature water bath.
16:49- The supernatant within test tube DEG was pippeted into another clean 20mL test tube. This test tube was labeled DEG-2 and was placed within the room temperature water bath.
16:51- The supernatant within test tube TEG was pippeted into another clean 20mL test tube. This test tube was labeled TEG-2 and was placed within the room temperature water bath.
16:54- The supernatant within test tube TetraEG was pippeted into another clean 20mL test tube. This test tube was labeled TetraEG-2 and was placed within the room temperature water bath.
16:56- The supernatant within test tube PEG was pippeted into another clean 20mL test tube. This test tube was labeled PEG-2 and was placed within the room temperature water bath.
16:57- The room temperature bath is at 25C.

2012-05-08

13:10- The solutions showed no signs of precipitation.