1858 ~ 1861, Kekulé, Couper, and Butlerov, laid the basis for one of the most fundamental theories in chemistry: the structural theory. Valence(化合价): C — tetravalent; O — divalent; H — monovalent
These spectra are often called carbon magnetic resonance (CMR) spectra or 13C NMR spectra. In some important ways 13C spectra are usually les complex and easier to interpret than proton (1H) NMR spectra