in Synthesis of para-Methylacetanilide What important bands (include chemical shifts) would begin to disappear in a H-1 NMR spectrum and what important bands would begin to appear in the H-1 NMR spectrum as the reaction progressed?
To determine the important bands that would begin to disappear and appear in the H-1 NMR spectrum during the synthesis of para-Methylacetanilide, we need to understand the starting material and the expected product. The starting material is acetanilide, which exhibits specific NMR peaks, and the product is para-Methylacetanilide.
First, let's consider the H-1 NMR spectrum of acetanilide as the starting material. Acetanilide typically shows the following proton signals in the NMR spectrum:
1. A singlet around 7.1-7.3 ppm: This signal corresponds to the aromatic protons (H-aromatic) of acetanilide.
2. A broad singlet around 3.9 ppm: This represents the amide proton (H-NHCOCH3) of acetanilide.
Now, as the reaction progresses and the synthesis of para-Methylacetanilide occurs, we can predict the changes in the NMR spectrum:
1. Disappearance of the H-NHCOCH3 signal: The amide proton in acetanilide (H-NHCOCH3) will react and be converted to a different functional group. Therefore, this broad singlet around 3.9 ppm will disappear in the H-1 NMR spectrum.
2. Appearance of methyl proton signals: In the product, para-Methylacetanilide, the amide group of acetanilide is replaced by a methyl group. Therefore, we can expect the appearance of new methyl proton signals (H3C) in the NMR spectrum. The exact chemical shifts of these methyl protons can vary depending on the specific substitution pattern. However, they typically appear as a multiplet or singlet around 2-2.5 ppm.
3. Retention of the H-aromatic signal: Since the aromatic portion (phenyl ring) of acetanilide is not modified in the reaction, the H-aromatic singlet signals around 7.1-7.3 ppm will generally be retained in the H-1 NMR spectrum of the para-Methylacetanilide product.
Note that the chemical shifts can slightly vary due to solvent, concentration, and other experimental conditions. It is always recommended to consult the actual experimental data and reference literature for accurate chemical shifts.
In summary, throughout the synthesis of para-Methylacetanilide, the H-NHCOCH3 signal from acetanilide will disappear, and new methyl (H3C) proton signals will appear in the H-1 NMR spectrum of the product, while the H-aromatic signals will be retained.