Objective

To determine the solubility of Diphenylacetic acid in methanol.



Procedure

A saturated solution of Diphenylacetic acid was prepared in methanol. In order to do so, a few crystals of the solute were added to a half dram vial. A Pasteur pipette was used to add some droplets of the solvent. The half dram vial was labeled, "O." After labeling, the vial was sonicated for 25 minutes. The solution was left to sit overnight. The following morning, vial "O" was sonicated again with 6 other vials from Experiment 078. After sonication, 100uL of the supernatant was removed from vial "O" and pippetted into an NMR tube. 700 uL of Chloroform D was also pippetted into the same NMR tube. This tube was capped and labeled NMR tube "O." The NMR tube "O" was tested and the results are displayed below.

Results

ONSCExp77-O - diphenylacetic acid in methanol [methyne proton at 5.022 ppm]


ONSC-EXP077 Baseline Correction Spreadsheet


ONSCeEXP077 Spreadheet


Discussion

The vial was sonicated twice though it could have been centrifuged instead. During the second sonication, the vial's lid fell off. Luckily, this was identified and fixed without any of the solution spilling into the bath. An extensive amount of shimming had to be done to generate this spectrum.

Conclusion

The 2.29 concentration value from this experiment is much different than the 1.18 value from EXP081. With the baseline correction, the concentration value changed to 1.36. This concentration value is 35% closer to the 1.18 value observed in EXP081.

The experiment was straight forward and simple as only one solute was tested. The spectrum has well defined peaks and the TMS shows a single peak at 0. The vortexing time should have been recorded in the log.

Log


2009-04-13

11:11 Labeled 1 half-dram vial O.
11:20 Placed a small amount of the solute (Diphenylacetic acid) in vial O
11:25 Pipetted out 300uL of methanol into the vial
11:30 Vortexed the vial
11:35 Placed vial O in sonicator at T=25C.
12:00 Vial O was taken out of soniactor. The bath temperature was 34C. Solid had formed at the bottom of the vial. The vial was left to sit for a day.

2009-04-14

16:55 Some of the solid from the previous night had dissipated back into the solvent. Therefore, vial O was placed in a small beaker with water and sonicated a second time along with the vials from Exp 078. The temperature of the beaker was 23C.
17:05 During sonication, the lid from vial A fell off. It was replaced by a new labeled vial.
17:25 All the vials were taken out of the sonicator. The temperature of the water in the beaker was 34C.
17:45 700 uL of CDCl3 were pipetted into a dry NMR tube labeled "O." 100 uL of supernantant was removed and placed into the NMR tube. No centrifuging or filtering was required. A substantial amount of solid had formed in the bottom of vial O so there was no need for centrifuging. After decanting into a second vial, the supernatant was easily pippetted out and placed in the NMR tube.
18:25 HNMR spectrum was obtained. Spectrum ONSCExp77-O is displayed in the results section.

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