Noves metodologies en RMN. II. Determinació de constants d'acoblament heteronuclears a llarga distància i aplicacions en anàlisi conformacional

For rigid systems of known geometry containing the H-C-C=C unit, it is proposed to measure the dependence of "super 3"J"sub CH" against the torsional angle 8. The relative contributions of the "sigma" and "pi" mechanism will be derived there of. The application to conformationally flexible systems will be preceded by molecular mechanics calculations of the populations of all conformers, and evaluation of their relative contribution to "super 3"J"sub CH". Experimental and calculated values will be systematically compared. Auseful tool for conformational analysis is expected.