Which of the following protons gives an NMR signal with the lowest chemical shift value (farthest upfield)?
A)1
B)2
C)3
D)4

Question

Which of the following protons gives an NMR signal with the lowest chemical shift value (farthest upfield)? 
A)1 
B)2 
C)3 
D)4

Quizplus · Accepted Answer

The proton that gives the lowest chemical shift value (farthest upfield) is the one that is most shielded from the magnetic field by the surrounding electron density. In this case, Proton 1 is located on an aromatic ring, which is very electron-rich and thus shields the proton from the magnetic field, resulting in a very low chemical shift value. Protons 2-5 are all located on aliphatic chains which are less electron-rich, and therefore less shielded.

Which of the Following Protons Gives an NMR Signal with the Lowest