Researcher

Jenna Mancinelli

Objective

To deternine the solubility curve of pyrene in acetonitrile at different temperatures.

Procedure


Label six vials. Add the following amounts of pyrene to vial 1 through 6, respectively: 25 mg, 30 mg, 35 mg, 40 mg, 45 mg, 50 mg. Add 1 g acetonitrile to each vial. Seal each vial tightly, and place them in a sonicator set to 36°C until all solutes are dissolved. Lower the temperature of the water in the sonicator until the solutes precipitate out. Record the temperature at which the solute precipitates.

Results

Spreadsheet-1
ONSCExp112-trend.JPG
[The solutions are too old now but next time take NMRs of the supernatant of one of the saturated solutions and the lowest concentration sample for SAMS confirmation JCB] Yes, none of the samples were saved for NMR, but next time this will be done.
[I have removed all the values from the SolSum sheet - just intrapolate to 22C and report that value there - all the other temperature dependent values go in the SolSumMix sheet JCB] Using the graph, it can be found that at 22C the concentration would be 0.1708 M.[show your plot for the intrapolation JCB]
Exp112.JPG


Discussion

Solubility of pyrene in non-aqueous solvents

According to expected trends of solubility versus temperature, as temperature increases concentration should increase, as well. This appears to hold true in this experiment except for the data point at 26C. At this point, the concentration decreases from 0.114 M to 0.138 M, making this data point questionable. At 36C, the concentration increases to 0.197 M, as is expected.
[It looks like vials 2 and 3 might have been mislabeled - if you switch these all the data fall into place JCB] While I do not believe I mislabeled the vials, I recognize that human error is a great possibility in this experiment. However, I think it appears that vials 3 and 5 were the two mislabeled. By switching these two data points, the concentration and temperature become directly proportional. If these points are switched, then at 22C the concentration would be 0.1532 M. Unfortunately, the samples no longer exist to try to varify this occurence.

Conclusion

A solubility curve of pyrene in acetonitrile at various temperatures was attempted. [The experiment will have to be repeated because a smoothly increasing solubility with temperature was not obtained. Also the verification of concentration by NMR needs to be done JCB]




Log

2009-06-14

14:30 Labeled 6 vials 1, 2, 3, 4, 5, 6
Weighed out and added pyrene to each vial
Vial 1: 28.1 mg
Vial 2: 31.9 mg
Vial 3: 36.2 mg
Vial 4: 42.6 mg
Vial 5: 44.8 mg
Vial 6: 49.9 mg
15:00 Each vial was tared to zero and then acetonitrile was added to each vial.
Vial 1: 1.042 g
Vial 2: 1.064 g
Vial 3: 0.995 g
Vial 4: 1.024 g
Vial 5: 1.050 g
Vial 6: 0.952 g
15:30 Each vial is sealed tightly and wrapped in parafilm. A copper wire with a label is attached to the lid of each vial to permit better labeling.
16:19 All six vials placed in sonicator at 36




Vial #
Pyrene (mg)
Acetonitrile (g)
1
28.1
1.042
2
31.9
1.064
3
36.2
0.995
4
42.6
1.024
5
44.8
1.05
6
49.9
0.952

17:00 Raised temperature within sonicator to 42°C by adding water that had been heated to 60°C to aid in the dissolving of the solutes. Continued to add hot water until all solutions were clear.
17:20 Began to lower temperature from 49°C using ice water (0°C). The solutes precipitated out according to the following chart:



Vial #
°C Precipitated
1
n/a
2
7
3
26
4
16
5
8
6
36

18:53 All vials provided a precipitate except for Vial 1, even aftering having sat in 0°C for several minutes.