Objective

To ascertain the solubility of phenylacetic acid in acetonitrile and toluene by NMR spectroscopy.


Procedure

Saturated solutions of phenylacetic acid were prepared in acetonitrile and toluene. The solutions were prepared by mixing together the solute and 300μL of the solvent into a vial. With each subsequent addition of solute, there were bouts of vortexing. Once the solutions showed an excess of solute, the vials were sonicated, using a Branson 1510 instrument, for 30 minutes. Solutions were then left to equilibrate. 100μL of the supernatants were micropipetted out and then dissolved into NMR tubes containing 900μL of deuterated chloroform (CDCl3) Proton NMR readings of the solutions are obtained with the use of a 300MHz instrument.


Results

Sample
Solvent
Solute
HNMR
HNMR Raw Data
Solubility (M)
1
Acetonitrile
phenylacetic acid
HNMR
phaceticacid-acetonitrile.jdx
3.87
2
Toluene
phenylacetic acid
HNMR
phaceticacid-toluene.jdx
1.94

Spreadsheet


Discussion

Saturated solutions in each solvent reported were obtained. This was verified by observation of solid solute contained within the sample vials after the sonication process. Therefore, the NMR spectra obtained could be held in confidence that the spectra were from a saturated solution, and that solubilities obtained from the spectra were validated.

This experiment, when it first began, had the intention of ascertaining the solubility of phenylacetic acid in methanol, ethanol, acetonitrile, THF, toluene, and DMSO. However, both the methanol and THF samples were lost when the caps unloosened and allowed water to enter the samples during the sonication process. The DMSO NMR result produces a spectra congruent to that of the ethanol sample. Therefore, I presume that I unknowingly saved a copy of the ethanol sample as the "DMSO" sample. The DMSO solution has since been discarded, so a new spectra could not be attained.

The ethanol sample was omitted for analysis, because upon looking at the spectra it was not easily discernable as to which peak corresponded to certain aspects of both the solute and the ethanol. For example, if you presume that the peak occuring at 4.2ppm corresponds to the methylene group of the solute and you take the peak occurring at 6.4ppm (or even that occurring at 7.4ppm) as that corresponding to the protons on the phenyl group, then the ratio of the peaks should be seen as 2:5; however, those peaks are no where near that ratio. Furthermore, upon zooming-in at the TMS peak, it was observed that there is lots of noise at the base line, as if a homogenized field was not obtained and there was a shimming issue. Lastly, it can also be observed that there is some peak overlapping present in the spectra, which furthermore makes it difficult to discern between the peaks attributed to the solute/or solvent.

In subsequent experiments, the half-dram vials with screw-on caps should be utilized to avoid the possibility of losing a sample during the sonication process. Also, once the sonication process has been completed, the vials should be centrifuged and then left to be equilibrated. In doing so, the remaining solute can pool to the bottom of the vial, and leave better access to the supernatant for retrieval. [another simpler approach is to filter using cotton in a Pasteur pipette JCB]

Conclusion

The solubility of phenylacetic acid has been determined in acetonitrile and toluene. The data obtained in this experiment shows that phenylacetic acid is capable of making 2M solutions for the Ugi product.

The Beilstein database is presently inaccessible (when attempting to update, an error presents when trying to update the calculator.jar file) , therefore other literature on the solubility of phenylacetic acid was not obtained.[We absolutely have to resolve this problem - contact the library to fix JCB]


Log

(includes Observations)

2009-05-7

13:35 Ambient temperature in the lab was measured to be 23°C.
13:44 A solution of phenylacetic acid in methanol was made by adding the solute to 300μL of methanol solvent in a vial labeled "methanol". Vortexed the vial briefly in-between additions, till the solute visibly collected at the bottom of the vial. Also, the reaction appeared to be endothermic, observed by the vial feeling cold to the touch with the immediate addition of solute to the solvent.
13:50 A solution of phenylacetic acid in ethanol was made by adding the solute to 300μL of ethanol solvent in a vial labeled "ethanol". Vortexed the vial briefly in-between additions, till the solute visibly collected at the bottom of the vial. Also, the reaction appeared to be endothermic.
13:56
A solution of phenylacetic acid in acetonitrile was made by adding the solute to 300μL of acetonitrile solvent in a vial labeled "acetonitrile". Vortexed the vial briefly in-between additions, till the solute visibly collected at the bottom of the vial. Also, the reaction appeared to be endothermic.
13:59 A solution of phenylacetic acid in DMSO was made by adding the solute to 300μL of DMSO solvent in a vial labeled "DMSO". Vortexed the vial briefly in-between additions, till the solute visibly collected at the bottom of the vial. Also, the reaction appeared to be endothermic.
14:06 A solution of phenylacetic acid in THF was made by adding the solute to 300μL of THF solvent in a vial labeled "THF". Vortexed the vial briefly in-between additions, till the solute visibly collected at the bottom of the vial. Also, the reaction appeared to be endothermic.
14:14
A solution of phenylacetic acid in toluene was made by adding the solute to 300μL of toluene solvent in a vial labeled "toluene". Vortexed the vial briefly in-between additions, till the solute visibly collected at the bottom of the vial. Also, the reaction appeared to be endothermic.
14:19 Parafilmed all vials.
14:21 Temperature of sonicator water was measured to be 25
°C.
14:22 Sonicated all vials for 30 minutes.
14:55 End temperature was measured to be 37°C.
14:56 Solutions were observed to no longer contain solute at the bottom of the vials. However, once the solutions rested briefly, solute began to quickly crash out. Also, the solute within the toluene solution crashed out to the point that the supernatant was no longer visible.
15:00 Added 100μL of toluene to the appropriate solution, briefly vortexed and parafilmed the vial.
15:02 Sonicated the toluene solution vial for 30 minutes. Beginning temperature measured to be 30°C.
15:35 End temperature after sonication was measured to be 36°C. Left all vials to equilibrate.

2009-05-8

13:08 The temperature within the lab was measured to be 19°C.
13:10 200μL of solvent was added to all vials, because no supernatant was visible. Briefly vortexed and parafilmed the vials.
13:23 Sonicated all vials for 30 minutes. Beginning temperature of 21°C.
13:54 End temperature 41°C. Left vials to equilibrate.
16:02 Added solute to the "methanol" and "ethanol" vials, parafilmed them both.
16:04 Sonicated the "methanol" and "ethanol" vials for 30 minutes, starting temperature began at 17°C.
16:34 "ethanol" vial was left to equilibrate. "methanol" sample was lost.
17:33 "ethanol" vial remained to be in an all liquid state.

2009-05-12

11:57 Temperature within lab measured to be 18°C.
12:01 "ethanol" vial was observed to have solid formation and supernatant present.
12:07 Added more solute to "THF" and "DMSO" vials, because there was no visible solute formation to notify that saturation had been reached. Briefly vortexed both vials and parafilmed them.
12:15 Added 400μL of toluene to respective vial.
12:18 Sonicated "THF", "DMSO", and "toluene" vials for 30 minutes. Temperature at sonicated was measured to be 17
°C.
12:50 The THF sample was lost (the cap popped off during sonication, which left the sample vulnerable to possible water intake). End temperature was measured to be 31°C. "DMSO" and "toluene" samples were left to equilibrate.
17:21 Temperature within lab measured to be 20°C.
17:22 Micropipetted 900μL of deuterated chloroform into 4 NMR tubes, labeled "ethanol", "acetonitrile", "toluene", and "DMSO."
17:24 Micropipetted 100μL of the supernatant from the
"ethanol" vial into its respective NMR tube. Mixed.
17:25 Micropipetted 100μL of the supernatant from the
"acetonitrile" vial into its respective NMR tube. Mixed.
17:28 Micropipetted 100μL of the supernatant from the "toluene" vial into its respective NMR tube. Mixed.
17:29 Micropipetted 100μL of the supernatant from the "DMSO" vial into its respective NMR tube. Mixed.
17:30 Obtained NMR spectra for all samples using the 300MHz Varian instrument.

References

Solubility of phenylacetic acid in acetonitrile (Solubility data viewer)
Solubility of phenylacetic acid in toluene (Solubility data viewer)


Compound
Inchi Key
Inchi
phenylacetic acid
WLJVXDMOQOGPHL-UHFFFAOYAR
InChI=1/C8H8O2/c9-8(10)6-7-4-2-1-3-5-7/h1-5H,6H2,(H,9,10)
Acetonitrile
WEVYAHXRMPXWCK-UHFFFAOYAJ
InChI=1/C2H3N/c1-2-3/h1H3
Toluene
YXFVVABEGXRONW-UHFFFAOYAT
InChI=1/C7H8/c1-7-5-3-2-4-6-7/h2-6H,1H3