| Abstract
| - The easy to use and free available graphical tool MestRe-J, developed for Win-32 platforms, calculates thevicinal proton−proton coupling constants 3JHH from the torsion angle φ between the coupled protons for thetwo kinds of generalized Karplus equations developed by Altona's group as well as for equations fromother authors. Besides the classical Haasnoot−de Leeuw−Altona equations, including individual substituenteffects that depend on their relative Huggins's electronegativities Δχ, the program incorporates the morerecent and precise Díez−Altona−Donders equations. The substituent effects in these equations, that includeeffects of interactions between substituents, depend on substituent parameters λ optimized from the 3JHHcouplings to methyl groups. Weighted time-averaged couplings can be calculated. The equations for 3JHHcan be solved to provide the torsion angles φ.
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