Solution Structure of Succinylacetone, An Unsymmetrical β-Diketone,As Studied by ~(13)C NMR and GIAO—DFT Calculations

摘要

The enolization degrees of succinylacetone, an important heme biosynthesis inhibitor, have beendetermined in CDCl_3 and water solutions using 1H NMR. The solution structures of SA have beeninvestigated using a combined NMR/theoretical [GIA0 DFT PBEIPBE/6-311++G(2d, p) PCM]approach. The populations of both enolic forms undergoing enol-enol equilibriums for SA and aseries of unsymmetrical 9-diketones have been established by a quantitative comparison of theexperimental ~(13)C NMR chemical shifts and calculated shielding constants. Moreover, using the samemethod and considering various trial structures differing in conformation and/or hydration ofneutral SA molecule as well as its monoanion and dianion the structures of the most abundant speciesbeing present in the investigated water solutions have been deduced.