Consider how the NMR spectrum of protons a in the compound changes on the addition of a trace of acid (assume that J_ab ≠ J_ac) :

Question

Consider how the NMR spectrum of protons a in the compound changes on the addition of a trace of acid (assume that J_ab ≠ J_ac):

Quizplus · Accepted Answer

The addition of a trace of acid would protonate the compound, likely on a different functional group than proton a. This would cause a change in the electron density around proton a, leading to a simplification of its NMR spectrum from a doublet of doublets to a simple doublet.

Consider How the NMR Spectrum of Protons a in the Compound