SNIF-NMR—Part 1: Principles

Abstract

Applications of high resolution deuterium-NMR in organic and bioorganic chemistry have regularly expanded in the last decades, accompanying the development of high field spectrometers which are required to overcome, at least in part, the severe drawbacks resulting from the nuclear properties of deuterium. In the technological conditions of the seventies both the small gyromagnetic ratio (4.107 {\texttimes} 107 rad/s/T), responsible for poor intrinsic sensitivity (9.6 {\texttimes} 10−3 with respect to 1H), and the very low natural abundance of deuterium (1.5 {\texttimes} 10−4) were serious impediments to the study of natural abundance deuterium spectra. Fortunately, the predominance of quadrupolar relaxation avoids perturbations in signal intensities due to nuclear Overhauser effects. Since 1980, more than 300 articles have been published in the field of high resolution 2H-NMR and, in this number, about 200 are concerned with quantitative determinations of isotope ratios, for which we have proposed the terminology SNIF-NMR (site-specific natural isotope fractionation studied by nuclear magnetic resonance). Both the first paper dealing with the NMR determination of non-random distributions of deuterium and the corresponding patent concerning applications appeared in 1981 [1,2].