2. The minimized structure of phenacetin is planar, and the chemical shifts of the aromatic protons in the NMR spectrum can be rationalized by electron delocalization. When drawn in the planar conformation, are any of the aromatic protons related by a valid symmetry operation? Explain why the resonances in the aromatic region produce two doublets instead of more complex splitting patterns.

Explanation:

Reason for the aromatic region shows two doublets:

1. Two types of protons present in the aromatic ring (Ha & Hb protons) based on their environment.

2. Two doublets are respectively shown to the two Ha protons in the ortho position and the two Hb protons in the meta position from the amide group.

3. Two Ha protons are coupled with two Hb protons.  

Summary: Two sets (Ha & Hb) of two equivalent protons (4 protons) present in the aromatic ring of Phenacetin. Two Ha protons are coupled with two Hb protons hence in the aromatic region two doublets are observed,

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.