Solubility Determination Procedure for 4-Chlorobenzaldehyde in Non-Deuterated Chloroform by Proton NMR


David Bulger

To develop a procedure that can be implimented in determining solubility by proton NMR using 4-chlorobenzaldehyde in non-deuterated chloroform.

Materials and Instrumentation
A JEOL 300-MHz high resolution 5-mm probe NMR was used with no spin and no lock at 22.4 °C. Shimming was performed followed by three NMR runs while the spin was temporarily working at 12-13 Hz with 2.0600 g reagent grade non-deuterated chloroform in an NMR tube. Mass determinations were performed using a 0.1 mg accuracy Sortorius balance. Shimming was performed followed by three NMR runs while the spin was temporarily working at 12-13 Hz with 2.0600 g reagent grade non-deuterated chloroform in an NMR tube.

Chloroform (1.9816 g; 1.3389 mL; 16.6 mmol) and 4-chlorobenzaldehyde (3.5 mg; 2.8 μL; 24.9 μmol) were added to a 5 mm NMR tube and gently mixed by manual inversion. This solution was then analyzed by 1H NMR.

Identification of Peaks on Standard Spectrum (282):
Identification Spectrum.pdf

Corrected Spectra
Raw JCAMP-DX file for NMR262
Raw JCAMP-DX file for NMR264
Raw JCAMP-DX file for NMR266

Results Spreadsheet

Photos of Experimental Equipment:



Since the JSpecView wasn't reading the JCAMP-DX Joint Committee on Atomic and Molecular Physical Data—Data Exchange) files correctly from the JEOL NMR, the orginal .jdx files were loaded into, processed with automatic baseline correction, exported into XY data points in both ppm and hz, ppm XY data points were transferred into the NMR262new.jdx file replacing the XY data points, and the data info sections were changed to match the new spectra. However, intXY.php still can't read the file.
The solution of 4-chlorobenzaldehyde in chloroform was predicted to have a molarity of 18.6 mM. By manually integrating (0.00001 min; 50%; 0%) the corrected spectra inside JSpecViewer, the molarity was calculated to be 19.8 mM for NMR262, NMR264, and NMR266. Considering the predicted molarity isn't exact due to solvated solute density calculations and the large difference in the peaks of the aromatic 4-chlorobenzaldehyde peaks and the chloroform signal, this calculation seems fairly accurate with a standard error of +6.7%.

The 18.6 mM solution of 4-chlorobenzaldehyde in chloroform was calculated by SAMS to be 19.8 mM with SE of +6.7%.


11.12.08 CST
10.18 – Weighed empty NMR tube.
10.20 – Added chloroform and recorded mass.
10.30 – First NMR run performed. 10.58 – Reweighed NMR tube.
11.00 – Added 4-chlorobenzaldehyde and recorded mass.
11.02 – Second NMR run performed.
12.12.08 CST
10.35 – Gradient shimming with deuterated chloroform at 12 Hz.
11.00 – NMR run performed on sample three times at 13 Hz.(Spectrum 262NMR262.jdx, Spectrum 264), Spectrum 266)
11:15 – Spin cock valve problem (spin was turned off).

1.16.09 CST

15.40 - Photos taken of equipment and reagents.


The author wishes to thank Dr. Robert Stewart for his advice throughout the course of the experiment and for the use of the NMR and other equipment, Dr. Jean-Claude Bradley for setting up the server for the interactive NMR spectra and the recommendation to use integration ratio comparision, and Dr. Antony Williams for his advice on improving the H NMR peaks

Previous Questions

[That is not enough 4-chlorobenzaldehyde to make a saturated solution in chloroform JCB] Good point, it would have to be saturated to determine solubilty.

[I am definitely interested in seeing the spectra. Magnetization equilibrium is assumed since you will have been shimming and the spins would have reached equilibrium magnetization during that period.How did you set the receiver gain to ensure that you didn't have saturation. Can you send me the spectra to take a look at? If you want I can then add them to the ChemSpider records. E.G: ChemSpiderman] The spectra are now posted in J-CAMP . Delta auto-gain was used to set the reciever gain. Future experiments may have higher resolution spectra. You can add any spectra you want to the ChemSpider records. Are there any specific spectra you would like me to send you?

[For this particular spreadsheet you need to show the calculation you did (integral values and peaks used) to come up with the ratio. You have multiple spectra but your spreadsheet only shows one measurement of the integrals. JCB] As far as the calculation of the ratio, I set the value of the integral of the chloroform peak equal to one and compared the other peaks in reference to it. This might now have been a good idea since the chloroform peak was so much bigger than the aldehyde peak.
[Specify exactly which region of the spectrum you used to measure the integrals so that it can be repeated by others. JCB] See Identification spectrum below.
[Calculate how much aldehyde you had in each of your measurements in the spreadsheet and compare with what you observe with the integration.with the ratio. JCB] That is a great idea.
What did you learn from this experiment? JCB]
Shimming yeilded smoother peaks than the no spin runs. Since the spin cock valve is temporarily not working, this shim value can be used for future experiments with 4-chlorobenzaldehyde in non-deuterated chloroform. Gentle mixing is not quantitative and sonication is recommended instead. The non-deuterated chloroform did not seem to interfere with the 4-chlorobenzaldehyde signals.
[I am interested in the exact procedure to perform the calculation to derive the solubility. Has this been explained in detail elsewhere? ChemSpiderman] This experiment was mainly a quick test to see if the peaks generated using this procedure were sufficient. As stated below, a few alterations were made to improve the quality of the peaks. The spin cock valve stopped spinning the sample above 4 Hz following shimming. This problem has been fixed and shimming and spinning of the sample will be implimented in experiments following EXP017. The solubility calculations were not performed in this experiment. EXP017 includes the method of calculating solubility.
[The way this experiment is done you will only be able to get the solubility as g/100g solvent or molar ratios - not molarity, which is our main unit to report solubility. You can get molarity and get spectra more easily if you make up a solution of a known concentration of a standard (say toluene in CDCl3) then mix a measured volume of this with a measured volume of your saturated solution and compare the integrals of the toluene with your solute. You will probably need micropipettes to do this properly. JCB] As for the volume of solvent, is it not possible to convert it from grams to liters using the density of chloroform? An external standard with water in a coax will most likely be used in future experiments.[In general an internal standard is more reliable JCB] Since I might not be defining my terms right, what I mean by an external standard is a coax insert inside the NMR tube with something like water in it to compare the ratios with, not the large external water standard outside the NMR tube. I consider an internal standard something placed in the solution that provides a comparision peak. I thought that an internal standard would cause the solubility to change.