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 understand the cause of the peak at 3.789 ppm, let's break down the information provided.
First, we know that the spectrum was obtained for fumaric acid in acetone. Therefore, we can assume that the majority of the observed peaks belong to fumaric acid, while the peak at around 2 ppm belongs to acetone.
Now, let's focus on the peak at 3.789 ppm. This peak is broad, indicating that the protons responsible for it experience a range of different electronic environments. Typically, broad peaks in NMR spectra are associated with protons that are involved in hydrogen bonding or are near functional groups such as hydroxyl (OH) or amine (NH).
Given that fumaric acid contains a carboxylic acid functional group (COOH), this peak is likely related to the protons in the carboxylic acid group. The integration value of 0.63 suggests that there are slightly fewer protons responsible for this peak than for the peak at 6.779 ppm, which belongs to a different set of protons in fumaric acid.
In summary, the peak at 3.789 ppm in the NMR spectrum of fumaric acid in acetone is likely due to the protons in the carboxylic acid group (COOH) of fumaric acid.