Question

The 1H-NMR spectrum of ethanol shows a triplet at 1.23 ppm, a singlet at 2.61 pm, and a quartet at 3.69 ppm. Assign each signal to the protons it corresponds to in the molecule. Explain the splitting pattern observed for each signal.

Answer 1

Proton NMR signals show split due to the presence of protons on the neighbouring Carbons. For ethanol, there are 2 carbons and 1 oxygen atom. CH3-CH2-OH.

The hydrogen bound to O will not show any split and will give a singlet signal at 2.61 ppm.

The 2 hydrogens on CH2 have 3 neighbouring hydrogens (CH3). Therefore CH2 hydrogens will be split into a quartet (# of neighbouring hydrogens + 1). This signal is seen at 3.69 ppm.

The 3 Hydrogens on CH3 have 2 neighbouring hydrogens (CH2). Therefore CH3 hydrogens will be split into a triplet. The signal is observed at 1.23 ppm.