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.

Question

Chemistry

Carmelo Summers

10 October, 03:14

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.

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Colin Molina · Answer 1

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,