1H NMR: Proton nuclear magnetic resonance

Abstract

This chapter highlights proton (1H) nuclear magnetic resonance (NMR). Proton NMR differs from 13C NMR in a number of ways. 1H is the major isotope of hydrogen, while 13C is only a minor isotope. 1H NMR is quantitative: the area under the peak shows the number of hydrogen nuclei, while 13C NMR may give strong or weak peaks from the same number of 13C nuclei. Moreover, protons interact magnetically (couple) to reveal the connectivity of the structure, while 13C is too rare for coupling between 13C nuclei to be seen. Finally, 1H NMR shifts give a more reliable indication of the local chemistry than that given by 13C spectra. Nevertheless, proton NMR spectra are recorded in the same way as 13C NMR spectra: radio waves are used to study the energy level differences of nuclei in a magnetic field, but this time they are 1H and not 13C nuclei.