Abstract

Over the years multidimensional NMR has become an essential tool for the structural analysis of molecules but, in practice, the most widely used experiment is still the 1D proton NMR, which, when properly interpreted, gives a wealth of information with minimal acquisition time and sample quantity. However, a detailed analysis of 1H-NMR, especially an automatic one, is often hindered by insufficient resolution (either digital or real), presence of extra lines (solvent and impurities), artifacts due to dead time and shimming, spectral lines overlap, strong coupling effects, etc.

Even though the theory of exact spectral analysis has been worked out over 40 years ago, automatic analysis of 1H-NMR is generally still performed by algorithms based on simple first order rules in which higher order effects (except, perhaps, rudimentary roof effects) are discarded, loosing a great amount of very valuable information.

In this work, we present our recent efforts aiming at an expert system which will overcome the difficulties mentioned and get the most out of 1D NMR spectra. If need be, the results obtained in this way can be complemented by information derived from more time consuming NMR techniques, such as 13C and multidimensional NMR experiments.

This expert system comprises a number of algorithms for boosting resolution and detecting spectral peaks, complete deconvolution of NMR data sets, quantum-mechanical simulation of spin systems of any size, automatic fitting of experimental spectra, novel ways to sort out the coupling structure between various multiplets, etc. Some of these algorithms extend in a natural way also to 2D spectra.