Nuclear Magnetic Resonance (NMR) Spectroscopy is not limited to the study of protons. Any element with a nuclear spin (13C, 17O, 19F, 31P and many others) will give rise to an NMR signal.Carbon- 13 NMR (13C NMR or referred to as carbon NMR) is the application of nuclear magnetic resonance (NMR) spectroscopy applicable to carbon. It is similar to proton NMR (1 H NMR) and allows the identification of carbon atoms whereas in other identification of H. As such 13C NMR is an important tool in chemical structure elucidation in organic chemistry. 13C NMR detects only the 13C isotope of carbon, whose natural abundance is only 1.1%, because the main carbon isotope, 12 C, is not detectable by NMR since it has zero net spin.The chemical shift of sp3 hybridized carbon atoms can be estimated with the help of an addivity rule using the shift value of methane and increments for substituents in α,β, positions.

Keywords: Nuclear magnetic resource, protons,nuclear spin, isotope,addivity rule .