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.

Procedure

Obtain five separate test tubes and fill each one with about 600mg of benzoic acid. Then mix 2mL of ethylene glycol within the first test tube, 2mL of diethylene glycol within the second test tube, 2mL of triethylene glycol within the third test tube, 2mL of tetraethylene glycol within the fourth test tube and 2mL 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 a minimum of 200C and higher). 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

Solbuilities could not be obtained.

Discussion

None of the glycol solutions precipitated out even after sitting in the room temperature water bath for over two days. It is 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

2012-05-09

13:25- A beaker was partially filled with water and placed on top of a hot plate. The hot plate was turned on to a setting of 4.
13:37- 0.9014g of benzoic acid was added into a 20mL screw-cap test tube labeled test tube EG.
13:40- 0.6445g of benzoic acid was added into a 20mL test tube labeled test tube DEG.
13:43- 0.6108g of benzoic acid was added into a 20mL test tube labeled test tube TEG.
13:46- 0.6015g of benzoic acid was added into a 20mL test tube labeled test tube TetraEG.
13:48- 0.6189g of benzoic acid was added into a 20mL test tube labeled test tube PEG.
13:56- The hot plate was turned to a setting of 8.
13:59- 2ml of ethylene glycol was added into test tube EG.
14:05- 2ml of diethylene glycol was added into test tube DEG.
14:06- The hot plate was turned to a setting of 9.
14:09- 2ml of triethylene glycol was added into test tube TEG.
14:12- 2ml of tetraethylene glycol was added into test tube TetraEG.
14:16- 2ml of polyethylene glycol was added into test tube PEG.
14:20- The water bath seems to be boiling (lots of steam coming out). All five of the glycol solutions were placed into the hot water bath.
14:21- Another water bath was prepared to be used as a room temperature water bath. The temperature of this water bath is at 26C.
14:30- Room temperature water bath is at 25C. The hot plate was turned off. The solids within the solutions dissolved only partially.
14:34- The supernatant within test tube EG was pipetted out and transfered into another small test tube labeled test tube EG-Sup. This test tube was then placed into the room temperature water bath.
14:37- The supernatant within test tube DEG was pipetted out and transfered into another small test tube labeled test tube DEG-Sup. This test tube was then placed into the room temperature water bath.
14:40- The supernatant within test tube TEG was pipetted out and transfered into another small test tube labeled test tube TEG-Sup. This test tube was then placed into the room temperature water bath.
14:42- The supernatant within test tube TetraEG was pipetted out and transfered into another small test tube labeled test tube TetraEG-Sup. This test tube was then placed into the room temperature water bath.
14:45- The supernatant within test tube PEG was pipetted out and transfered into another small test tube labeled test tube PEG-Sup. This test tube was then placed into the room temperature water bath.

2012-05-11

10:10- None of the test tubes within the room temperature water baths showed any signs of precipitation.