An NMR spectrum of fumaric acid in acetone was run. The following results were obtained:
1 sharp peak with 5 splittings at around 2 ppm (belonging to acetone)
1 broad peak at 3.789 ppm (integration 0.63)
1 sharp peak at 6.779 ppm (integration 1.00) (belonging to CH of fumaric acid)
1 even broader peak at 11.387 ppm (integration 0.52) (belonging to COOH of fumaric acid)
What is the cause of the peak at 3.789 ppm?
To determine the cause of the peak at 3.789 ppm, we need to consider the NMR chemical shifts of common functional groups and compare them to the experimental data provided.
First, let's look at the peak at 2 ppm. This peak belongs to acetone, which is the solvent used in this NMR experiment. The presence of 5 splittings indicates that the protons in acetone are interacting with neighboring protons, resulting in splitting of the signal.
Now, let's focus on the remaining peaks. The peak at 6.779 ppm is a sharp peak with integration 1.00, which suggests a single set of protons. This peak belongs to the CH group in fumaric acid.
Next, we have a broad peak at 11.387 ppm with integration 0.52, which suggests multiple sets of protons. This peak belongs to the COOH group of fumaric acid.
Finally, we come to the peak at 3.789 ppm with integration 0.63. To determine the cause of this peak, we can compare the chemical shift with known functional groups. In this region, a common functional group that resonates around 3.7-4.0 ppm is the CH2 group, particularly in compounds like aldehydes, ketones, and ethers.
Based on this information, it is likely that the peak at 3.789 ppm is due to the CH2 group present in fumaric acid. The broadness and integration value suggest that there might be additional splitting or coupling within this functional group.
In summary, the peak at 3.789 ppm is attributed to the CH2 group in fumaric acid.