Which of the following functional groups has the most deshielded proton and would be predicted to show an NMR signal that is the farthest downfield?
A) benzylic - H
B) allylic - H
C) aldehyde - H
D) aromatic - H
E) acetylenic - H

Question

Quizplus · Accepted Answer

The aldehyde proton (C=O-H) has the most deshielded proton because it is directly attached to an electronegative oxygen atom, which withdraws electron density from the proton. This results in a greater chemical shift and a signal that appears farthest downfield in the NMR spectrum.

Which of the Following Functional Groups Has the Most Deshielded