Use of indirect 199Hg NMR detection for aromatic mercury compounds of biological interest

Abstract

AbstractWhen vanillin (4‐hydroxy‐3‐methoxbenzaldehyde) and syringaldehyde (4‐hydroxy‐3,5‐dimethoxybenzaldehyde) react with Hg(OAc)2, selective monomercuration occurs on the aromatic ring. The three 3J, 4J and 5(199Hg,1H) coupling constants of phenylmercury acetate were used as 1/2J delays in the 1D inverse 1H 199Hg, sequence applied to 5‐acetoxymercuriovanillin and 2‐acetoxymercuriosyringaldehyde, the edited proton spectra obtained for each nJ(199Hg, 1H) coupling gave the value of n and the J(199Hg, 1H) coupling constants, and therefore yielded information about the position of the mercury substitution on the aromatic ring. A 2D 199Hg,1H shift correlation with 1H detection was applied in the case of phenylmercury acetate, using the mean value of the three J couplings; the 3J and 4J couplings were clearly resolved. As vanillin and syringaldehyde are representative monomer models of lignin, the indirect detection of 199Hg is then an appropriate method to determine the aromatic substitution pattern, which is a key point in lignin structural elucidation.