Researcher

Rida Atif

Objective

To determine the solubility at room temperature of cinnamic acid in hexane and in cyclohexane

Procedure

Two large screwcap tubes were obtained and each were filled with some cinnamic acid. The tubes were labeled either A or B; a generous amount of hexane was added into Tube A while cyclohexane was added into Tube B. The tubes were attached to an apparatus that would submerge them into a 25C water bath while simultaneously shaking them on a shake plate. The tubes were allowed to shake for 24 hours. After 24 hours, the tubes were removed and 1mL of the supernatant from each tube was measured into a 1mL volumetric flask. The 1mL from the flask was transferred to a 10mL volumetric flask. The 10mL volumetric flask was filled with methanol or ethanol (two trials were done of each tube with different solvents to dilute them). Doing this the first time creates a 10 fold dilution. 1mL of the 10 fold dilution was taken and put into a 1mL volumetric flask and the process was repeated to create a 100 fold dilution, then once more to create a 1000 fold dilution. A cuvette was filled with the 1000 fold dilution solution and another was filled with the pure solvent used to dilute it and a UV spectra was taken of the sample.

Results

CALCULATION SHEET
UV Spectra pure methanol
UV Spectra pure ethanol

UV Spectra Tube A 24 hours (1000 dilution) in methanol
Concentration: 0.03209M
UV Spectra Tube B 24 hours (1000 dilution) in methanol
Concentration: 0.01551M
UV Spectra Tube A 24 hours (1000 dilution) in ethanol
Concentration: 0.0184M
UV Spectra Tube B 24 hours (1000 dilution) in ethanol
Concentration: 0.0184M

Discussion

At first, when the dilutions were created and UV spectrums were taken, acetone was used to clean out the cuvette and flasks in between uses. The use of acetone affects the concentration calculated because it absorbs in the same region as methanol. Also, while making the [[#|1000]] fold dilution of Tube A, it was noticed afterwards that the solution went slightly above the 10mL mark in the volumetric flask which also affected the final concentration calculated. Methanol was not a good choice in reference solvent; one of the reasons is because there were discrepancies in the extinction coefficients reported in various papers as well as the grade of the methanol which was not spectral grade. Ethanol would be a much better choice.
When the spectrum was done again without the use of acetone and with ethanol as the solvent to dilute the solution in, the concentration ended up being about the same for cyclohexane. The interesting thing about the ethanol dilution was that it resulted in the same concentration for both hexane and cyclohexane; they both had the same absorption at the same peak.
According to the calculations done to figure out the recrystallization yields, the room temperature solubility should be higher if that is the factor causing discrepancies in the [[#|recovery]] yields. The difference in the concentrations of hexane with methanol versus ethanol can be accounted for by the use of acetone while diluting the solution with methanol. Another possibility is that the extinction coefficients used are not accurate.

Conclusion

It would be beneficial to determine the extinction coefficient for cinnamic acid in methanol and in ethanol just to verify if the correct ones were being used to calculate concentrations.
It would also be beneficial to repeat the procedure of EXP244 in which the room temperature solubility of cinnamic acid in hexane was determined via the density method.

Log

2012-08-01

10:46 - A large [[#|screw cap]] tube (Tube A) was filled with 0.7873g of cinnamic acid
10:52 - 4.932g of hexane was added into Tube A
10:55 - Another large screw cap tube (Tube B) was filled with 0.775g of cinnamic acid
10:59 - 5.337g of cyclohexane was added into Tube B
11:02 - Both of the tubes were covered in parafilm at the top and attached to an apparatus that would submerge them into a 25C water bath while shaking them via a shake plate
11:07 - The shake plate was turned on to setting 3

2012-08-02

11:18 - The shake plate was turned off and the two vials were removed from the apparatus
11:35 - 1mL of the supernatant from Tube A was measured into a 1mL volumetric flask, then moved to a 10mL volumetric flask
11:40 - methanol was added into the 1mL volumetric flask and then moved to the 10mL flask to ensure all of the supernatant has been moved to the 10mL flask. Methanol was added until the 10mL volumetric flask was filled to the mark. This makes this solution a 10 fold dilution
11:50 - 1mL of the supernatant from Tube B was measured into a 1mL volumetric flask, then moved to another 10mL volumetric flask.
11:47 - methanol was added into the 1mL volumetric flask and then moved to the 10mL flask to ensure all of the supernatant has been moved to the 10mL flask. Methanol was added until the 10mL volumetric flask was filled to the mark. This makes this solution a 10 fold dilution.
12:04 - Two 1cm cuvettees were obtained. One was filled with pure methanol while the other was filled with the 10 fold dilution of Tube A
12:15 - EXP330TubeA-24hours10dilution was run on UV/vis spectroscopy machine
12:30 - The cuvette containing sample from Tube A was washed and dried and filled with the 10 fold dilution of Tube B
12:40 - EXP330TubeB-24hours10dilution was run on UV/vis spectroscopy machine
12:56 - The cuvette was washed and dried again and filled with the 10 fold dilution of Tube A again to run on machine again due to a slightly skewed spectrum
13:10 - 1mL of the 10 fold dilution of Tube B was measured into a 1mL volumetric flask and moved to another 10mL volumetric flask. Methanol was added into the larger flask until it hit the mark. This solution is a 100 fold dilution; however this may be too much so this is going to diluted again
13:18 - 1mL of the 100 fold dilution of Tube B was measured into a 1mL volumetric flask and moved to another 10mL volumetric flask. Methanol was added into the larger flask until it hit the mark. This is a 1000 fold dilution.
14:02 - 1mL of the 10 fold dilution of Tube A was measured into a 1mL volumetric flask and moved to another 10mL volumetric flask. Methanol was added into the larger flask until it hit the mark. This solution is a 100 fold dilution.
14:08 - 1mL of the 100 fold dilution of Tube A was measured into a 1mL volumetric flask and moved to another 10mL volumetric flask. Methanol was added into the larger flask until it the mark. This is a 1000 fold dilution.
2:47 - A UV spectrum was taken of each sample. It was noticed here that acetone should not be used to wash the glassware while running a UV spectrum. Each of the samples will have to be taken again, with ethanol as a reference and no use of acetone.

2012-08-03

11:15 - 1mL of the supernatant from Tube A was measured into a 1mL volumetric flask.
11:16 - The 1mL in the volumetric flask was transferred to a 10mL volumetric flask
11:25 - Ethanol was put into the 1mL flask and then put into the 10mL flask to ensure all of the supernatant has gone to the larger flask. This was done until the 10mL flask was filled to the mark. This is a 10 fold dilution.
11:37 - The last two steps were repeated once again to create a 100 fold dilution
11:45 - This process was repeated once more to create a 1000 fold dilution.
11:48 - 1mL of the supernatant from Tube B was measured into a 1mL volumetric flask.
11:50 - The 1ml in the volumetric flask was transferred to a 10mL volumetric flask
12:02 - Ethanol was put into the 1mL flask and then put into the 10mL flask to ensure all of the supernatant has gone to the larger flask. This was done until the 10mL flask was filled to the mark. This is a 10 fold dilution.
12:11 - The last two steps were repeated once again to create a 100 fold dilution
12:17 - This process was repeated once more to create a 1000 fold dilution.