37.4.1—Proton NMR interpretation

A proton NMR spectrum reveals different proton environments. The integration trace gives relative numbers of protons, and splitting shows coupling to neighbouring non-equivalent protons.

Build a structure by combining three clues: number of signals, relative integrals and chemical-shift regions. Use the n+1 rule for simple adjacent proton sets, then check the total hydrogen count.

An ethyl group gives a triplet for CH₃ and a quartet for CH₂ with an integral ratio 3:2; an isolated OH may appear as a broad singlet.

A quartet does not mean four protons: it usually means one proton set is split by three neighbouring protons.