EXP_261_all_3_molecules.png
Daly, Jacob A. Steph Molecules 2. PNG.


[include image of other hemiacetal JCB]

Researcher

Stephanie Costa

Objective

To determine the the ratio of hemiacetal ((4-Chlorophenyl)(ethoxy)methanol) to aldehyde produced as a result of 4-chlorobenzaldehyde in ethanol and the ratio of hemiacetal ((4-Chlorophenyl)(methoxy)methanol) to aldehyde produced as a result of 4-chlorobenzaldehyde in methanol at 0.2 M concentration. [link to entries for the 4 compounds on ChemSpider JCB]

Procedure

0.2M solutions of 4-chlorobenzaldehyde in ethanol and 4-chlorobenzaldehyde in methanol were created at room temperature. An NMR was then taken of both the solutions using CDCl3.

Results

Calculations sheet
[include calculation sheet JCB]
0.2M Samples were created

NMR data sheet
[error in one hemiacetal SMILES, mw, etc. number of Hs for methanol wrong, one spectrum name wrong JCB]
[specify the concentrations and ratios observed - one number you currently have as calculated by the sheet can't be right - look at the region manually to see if you can make sense of it JCB]

The ratio of aldehyde to hemiacetal in ethanol was 12.714.
The ratio of aldehyde to hemiacetal in methanol was trace. The numbers calculated by the data sheet are incorrect.

Discussion


In 4-chlorobenzaldehyde in ethanol:
Aldehyde peak was seen at 9.979 ppm.
CDCl3 peaks were seen at 7.550 and 7.815 ppm.
Hemiacetal was seen at 5.6148 ppm and 5.6294 ppm and it coupled with the OH (peaks at 6.436 and 6.452 ppm). The distance between the peaks was 7.5 Hz.
Ethanol was at 1.2054 ppm.
TMS was at 0 ppm (the results were zeroed using TMS).

In 4-chlorobenzaldehyde in methanol:
Aldehyde peak was at 9.977 ppm.
CDCl3 peaks were seen at 7.555 and 7.8472 ppm.
Hemiacetal was visible at 5.536 and 5.522 ppm. The hemiacetal coupled with the OH (peaks at 6.360 and 6.375 ppm). The distance between the peaks was 7.25 Hz.
Methanol was seen at 3.416
TMS was at 0 ppm (the results were zeroed using TMS).

The ratio of hemiacetal to aldehyde in ethanol was 12.714
the ration of aldehyde to hemiacetal in methanol was non existent or trace amounts were seen. In the integration of the NMR data, there is no indication of the hemiacetal peak in that sample.

These ratios do not compare favorably to the ratio in the blog post. However, there many have been factors that affected the results. Firstly, the solution were only allowed to sit for 20 minutes and many not have reached equilibrium yet. Secondly, 1 mL of CDCl3 was used, which could have diluted the ratio. The concentration was small to begin with, so diluting it further could have affected the ratio.

The ethanol peak was extremely close to the value reported in the MIT paper. [How do these results compare with previous reports? JCB]

Conclusion

The ratio of aldehyde to hemiacetal in ethanol was 12.714. The ratio of aldehyde to hemiacetal in methanol was not great enough for a conclusion.

Log

2012-02-20

13:15- 2 25mL flasks were cleaned and dried
13:34- 0.2811g of 4-chlorobenzaldehyde was added to flask 1
13:37- 0.2811g of 4-chlorobenzaldehyde was added to flask 2
13:39- 10 mL of methanol was added to flask 2. The solution was pipetted in and out to mix and then covered with parafilm.
13:43- 10mL of ethanol was added to flask 1. The solution was pipetted in and out to mix and then covered with parafilm.
13:50- solute was seen in both flasks. The flasks were swirled for 10 seconds.
13:57- both flasks were swirled. No solute was seen. About 1 mL of CDCl3 and about 0.5 mL of solution was mixed in a vial. This was repeated for the other sample. About 1mL of each mixture was transferred to a NMR tube and capped.
14:13- The samples were ran on a 500 Hz NMR. The sample with ethanol was ran first. The sample was zeroed using TMS and the data was saved as a dx file "scostaEXP261_ethanol.dx" (then loaded into JSpecView and exported as XY). [name the NMR files here JCB]
14:22- the methanol sample was ran. The sample was zeroed using TMS and saved as a dx file "scostaEXP261_methanol".