Which of the indicated protons in the molecules below would absorb furthest downfield in a ¹H NMR spectrum?

Question

Quizplus · Accepted Answer

Proton II would absorb furthest downfield as it is attached to a carbonyl group, which results in deshielding due to the electron-withdrawing effect of the oxygen atom. The proton I is also attached to a carbonyl group, but it is shielded by the nearby methyl group. Proton III is attached to a carbon atom, which is not significantly deshielding. Proton IV is attached to a hydrogen atom, which is also not significantly deshielding.

Which of the Indicated Protons in the Molecules Below Would