Objective

To ascertain the solubility of 4-hydroxybenzaldehyde in THF by NMR spectroscopy.


Procedure

Saturated solutions of 4-hydroxybenzaldehyde in THF solvent were prepared by adding excess solute to THF in a half-dram vial. The vials were vortexed for approximately 10 seconds and if necessary, more solute was added until after vortexing, precipitate remained on the bottom of the vial. The vials were sonicated for 30 minutes and if necessary, more solute was added until solid remained for 30 minutes of consecutive sonication. The supernatant was then removed from the vials either by Pasteur pipette or by filtration. NMR tubes were labelled 1', 2', and 3' for each vial. 2-3 drops of the supernatant were added to 700uL of CDCl3 in the appropriate NMR tubes. If precipitate was seen in the NMR tubes, 1-2 drops of DMSO-d6 was added to the solution. An NMR of each sample was taken on the 300MHz Variac instrument.

Results



Spectra

ONSCExp088-1
ONSCExp088-2
ONSCExp088-3
Raw data for JCAMP dx file ONSCExp088-1
Raw data for JCAMP dx file ONSCExp088-2
Raw data for JCAMP dx file ONSCExp088-3

Discussion

The concentration values of 4-hydroxybenzaldehyde in THF measured in this experiment were verified when compared to other experiments using the same solvent and solute[1]. Exp058and Exp085 reported concentration values of 3.58M and 3.91M respectively. This experiment generated values of 3.59M, 3.72M, and 3.88M, thus the proximity of all concentration values confirms that this experiment was successful.
The 4-hydroxybenzaldehyde was soluble in THF, however upon addition of CDCl3, some solute crashed out of solution. As 4-hydroxybenzaldehyde is a phenol, it had a low solubility in the deuterated solvent and came out of solution. Addition of 2-3 drops of DMSO-d6 forced the precipitate back into solution, thus yielding a saturated solution. This phenomenon was not reported in any previous experiments with the same solute and solvent, thus it is not yet known whether this was due to experimental error.

Conclusion

The solubility of 4-hydroxybenzaldehyde in THF was found to be 3.59M, 3.72M, and 3.88M. The mean value was 3.73M and the standard deviation was 0.119.


Log

2009-05-11
11:13--Labelled 3 Vials "1, 2, and 3"
11:15--Added 300mL of THF in Vial 1. After adding a scoop of 4-hydroxybenzaldehyde, the vial was capped and vortexed for approximately 10 seconds. This was repeated 4 times and the solution was found to be saturated.
11:20--Added 300mL of THF in Vial 2. After adding a scoop of 4-hydroxybenzaldehyde, the vial was capped and vortexed for approximately 10 seconds. This was repeated 4 times and the solution was found to be saturated.
11:27--Added 300mL of THF in Vial 3. After adding a scoop of 4-hydroxybenzaldehyde, the vial was capped and vortexed for approximately 10 seconds. This was repeated 4 times and the solution was found to be saturated.
11:38--Set vials in a small beaker filled one-third with water and placed in the sonicator. The temperature was read at 19.0C and the timer was set for 30 minutes.
11:56--Vials were removed from sonicator early as no more solid was present.
11:58--One scoop of 4-hydroxybenzaldehyde was added to Vial 1, and the vial was capped and vortexed for approximately 10 seconds and the solution was found to be saturated.
12:00--One scoop of 4-hydroxybenzaldehyde was added to Vial 2, and the vial was capped and vortexed for approximately 10 seconds and the solution was found to be saturated.
12:02--One scoop of 4-hydroxybenzaldehyde was added to Vial 3, and the vial was capped and vortexed for approximately 10 seconds and the solution was found to be saturated.
12:04--Set vials in a small beaker filled one-third with water and placed in the sonicator. The temperature was read at 27.0C and the timer was set for 30 minutes.
12:08--Vials were removed from sonicator early as the solutions were no longer found to be saturated.
12:09--One scoop of 4-hydroxybenzaldehyde was added to Vial 2, and the vial was capped and vortexed for approximately 10 seconds and the solution was found to be saturated.
12:11--One scoop of 4-hydroxybenzaldehyde was added to Vial 3, and the vial was capped and vortexed for approximately 10 seconds and the solution was found to be saturated.
12:13--Set vials in a small beaker filled one-third with water and placed in the sonicator. The temperature was read at 27.0C and the timer was set for 30 minutes.
12:41--Vials 2 and 3 removed from the sonicator. One scoop of 4-hydroxybenzaldehyde was added to vial 1 and it was capped, vortexed for 10 seconds, and set in the sonicator for 30 minutes at 29.5C
13:01--Vials 2 and 3 were centrifuged for 5 minutes, thus yielding the saturated solutions at 21.0C
13:10--Vial 3 was filtered; the contents of the vial were added to a pasteur pipette packed with cotton and passed through the cotton thus filtering off solids and collecting the saturated solution in another vial, 3'.
13:11--Vial 1 was removed from the sonicator and centrifuged for 5 minutes, yielding a saturated solution at 21.0C
13:12--Vial 3' was mixed with 750uL of CDCl3 in an NMR tube. Some orange/brown solids crashed out of solution thus suggesting the 4-hydroxybenzaldehyde phenol was insoluble in CDCl3.
13:18-- The saturated solution in Vial 1 cleanly separated from the remaining precipitate, thus 3-4 drops of solution were pipetted into a vial, 1', and mixed with 750mL of CDCl3. Vial 1' also had precipitate crash out of solution, thus it too was insoluble in CDCl3.
13:24--Two or three drops of DMSO-d6 were added to Vials 1' and 3', to get the solids back into solution
13:27--Vials 1' and 3' were sonicated at 26.0C for 3 minutes in their NMR tubes, and the tubes were set aside.
20:00--The NMRs of 1', ONSCExp088-1XY, and 3', ONSCExp088-3XY, were taken on the 300MHz NMR instrument.

2009-05-12
16:03--Vial 2 was filtered; the contents of the vial were added to a pasteur pipette packed with cotton and passed through the cotton thus filtering off solids and collecting the saturated solution in another vial, 2'.
16:12--The contents of 2' were placed in an NMR tube with 700uL of CDCl3. Some orange/brown solids again crashed out of solution. NMR tube 2' was vortexed for approximately 10 seconds. 2-3 drops of DMSO-d6 were added to 2', and most of the precipitate went back into solution.
16:13--NMR tube 2' was sonicated for 2 minutes at 23.0C
16:19--The NMR of 2', ONSCExp0882-XY was taken on the 300MHz instrument.

References

[1] Solubility of 4-hydroxybenzaldehyde in THF

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