When doing 1H-NMR, what is the chemical reason why an the hydrogen in an OH group sometimes shows up at different ppm locations? For propan-2-ol, I found a doublet at 4.88ppm, which makes a lot of sense due to the n+1 rule, but some of the literature values show singlets, sometimes at different ppm values, and some literature does not show a peak for this hydrogen at all. My lab report requires that I explain what molecular interactions are responsible for this phenomenon. Thank you! Solution The oxygen in OH gp cause the shielding of protons and thus a diiferent ppm location is shown by OH . Hence this behaviour is due to the shielding and dishielding phenomenon of proton NMR . .