EXP_258_2_molecules.png
Daly, Jacob A. Steph Molecules. PNG.

Researcher

Stephanie Costa

Objective

To determine the solubility of 4-chlorobenzaldehyde in ethanol and methanol at 25C. The additivity of the volumes is assumptive .

Procedure

A solution of 4-chlorobenzaldehyde and ethanol (1) and 4-chlorobenzaldehyde and methanol (2) were made by adding the reactants and stir bars. The two solutions were left on a stir plate.

Results

NMR results for ethanol

The two solutions were not saturated.
From the 4-chlorobenzaldehyde and ethanol solution (after the 0.25 ppm correction):
The aldehyde was seen at 9.504 ppm [Are these numbers before or after the 0.25 ppm correction?]
Ethanol was seen at .753 ppm [Provide the actual peak location - not a range JCB]
CDCl3 peaks were at 7.0441 and 7.0605 ppm [Provide the actual peak location - not a range JCB]
Hemiacetal peak was seen at 5.025 ppm [Provide the actual peak location - not a range JCB]
The ratio of aldehyde to hemiacetal was 1.8:1

Calculation sheet

Discussion

The solution of 4-chlorobenzaldehyde and ethanol was not saturated when the NMR was performed, therefore the solubility was not determined. A NMR of the solution of 4-chlorobenzaldehyde and methanol was not taken due to time constraints and my class schedule. [Why? JCB]

All of the results were shifted .25 ppm to the left, the NMR was not zeroed.
The shift was determined by the MIT paper that outlined which peaks should be seen at what ppm.

There were problems with the NMR. Side bands were seen, for unknown reasons. There was construction outside, which may have affected the NMR machine.

This experiment is similar to the experiment outlined in this blog post which shows consistencies to other aldehydes with electron-drawing groups, including a 2:1 ratio of aldehyde to hemiacetal. [be a bit more specific about ratios reported JCB]

[What effect could the addition of CDCl3 have on the hemiacetal/aldehyde ratio? JCB]
The addition of CDCl3 could have diluted the solution, altering the hemiacetal/aldehyde ratio. The ratio might not be as high as it should.

Conclusion

The ethanol hemiacetal 4-chlorobenzaldehyde was found to be in the ratio of 1:1.8 to aldehyde at about 2M (adding both components)

Log

2012-2-8

11:30- two 25mL flasks were cleaned and dried
11:44- 2.2681g of 4-chlorobenzaldehyde were placed into flask 1.
11:50- Ethyl alcohol (100%) was filled to the 20mL line. a stir bar and parafilm were added. flask 1 was placed on a stir plate at 60 rpm. The room temperature was 20C.
11:55- 2.3387g of 4-chlorobenzaldehyde was placed into flask 2
11:59- methanol was added to the 20mL on flask 2. A stir bar and parafilm were added. flask 2 was placed on the stir plate at 60rpm. All the solute in both flasks was taken into the solution.
12:02- 1.4900g 4-chlorobenzaldehyde was added to flask 1. flask 1 was recovered and placed back on the stir plate.
12:05- 1.4857g 4-chlorobenzaldehyde was added to flask 2, which was then recovered and replaced to the stir plate.
13:36- All of the solute was integrated into the solution. 1.4721g 4-chlorobenzaldehyde was added to flask 1, which was then recovered and placed back on the stir plate.
13:38- 1.4947g 4-chlorobenzaldehyde was added to flask 2, which was then recovered and placed back on the stir plate. The stir plate was 75 rpm.
13:41- the room temperature is 20C.
13:46- 1.4174g 4-chlorobenzaldehyde was added to flask 1, which was then recovered and placed back on the stir plate.
13:48- 1.5570g 4-chlorobenzaldehyde was added to flask 2.
14:02- 1.4687g 4-chlorobenzaldehyde was weighed out.
14:08- that sample was added to flask 1, which was then recovered and replaced on the stir plate. 1.4032g 4-chlorobenzaldehyde was added to flask 2, which was recovered and replaced on the stir plate.
14:29- the mass of ethanol were taken. the empty 1mL volumetric flask was 42.8273g. the ethanol (and flask) was 43.6228g.
14:32- the mass of methanol was taken. the empty 1mL volumetric flask was 42.8273g. the methanol (and flask) was 43.6177g. Solute was seen in flask 1 and no solute was seen in flask 2.
14:40- 5mL of solution was removed from flask 2
14:42- 2.2685g 4-chlorobenzaldehyde was added to flask 2, which was recovered and replace on the stir plate.

2012-2-10

14:16- NMR (500 microHz) 1A of flask 1 (4-chlorobenzaldehyde and ethanol) was performed using CDCl3. About 1mL of the solution was mixed with 1mL of CDCl3. The 1mL of the mixture was pipetted into the NMR tube. The file was originally saved as a dx file, then later converted to a jdx file.