During my PhD, I prepared the two compounds below (there was actually a slightly longer chain but it's not inherently relevant).
When looking at the 1H NMR spectra of these compounds, something slightly weird occurred.
In one of them, the CH2 group of the benzyl appeared as a singlet (s, 2H). In the other, the CH2 group of the benzyl was observed as a multiplet (an AB quartet like structure, to be specific).
Is there any rationale for why the two cases would be different, given the distal nature of the closest stereocentre (i.e. why are the two CH2 protons diastereotopic to begin with given how distal they are)?