Abstract: The influence of Fe(Ⅲ) on ¹³C NMR signals of aliphatic acids was studied. It is shown that the machanism of the influence is the effect of electron spin relaxation on nuclear relaxation and the necessary factor of the influencc is the complexing between Fe(Ⅲ) and the aliphatic aled. It is indicated that the influence weakens rapidly with the increase of the distance. The normal spectra can be obtained by destroying the complexing between Fe(Ⅲ) and the aliphatic acid. This phenomenon can be used to help assign the ¹³C NMR spectra of some compounds. Fe(Ⅲ) may be used as a probe to study the behvaior of some organic compounds in solution.

Key words: ¹³C NMR, Aliphatic acids, Paramagnetic substance