Helmut Herzog

Influence of extractant and soil type on molecular characteristics of humic substances from two brazilian soils

In a previous study it was observed that humic substances (HS) extracted with NaOH solution and with Na4P2O7 solution presented different molecular weights, and also that the extracted HS yield by each method varied between an Oxisol and a Mollisol from South Brazil. In the present study, we further investigated the organic matter in these soils by characterizing HS extracted with 0.5 mol L-1 NaOH and with neutral 0.15 mol L-1 Na4P2O7 solutions from the above mentioned samples, using elemental analysis and nuclear magnetic ressonance spectroscopy (liquid state 1H- and 13C-NMR), and by relating the molecular differences to the extraction method and soil type. HS extracted with pyrophosphate were more humified, showing a higher aromaticity and higher carboxylic content. The NaOH-extracted HS were more aliphatic and contained a higher O-alkyl proportion, which is indicative of a less humified nature than the pyrophosphate-extracted HS.

Hydroacridines. Part 17—Stereospecific influence of the N+—O‐ group on 1JC,C couplings in non‐aromatic amine oxides

The 1JC,C coupling constants of N‐epimeric pairs of amine oxides derived from (4aα, 8aβ, 9aβ, 10aα)‐ and (4aα, 8aα, 9aβ, 10aα)‐tetradecahydro‐10‐methylacridine, 1‐cis‐2,6‐trimethylpiperidine and tropine were investigated and compared with those for the parent amines. For C—C bonds adjacent to the N+—O‐ group, the couplings depend on the mutual orientation of the N+—O‐ bond and the C—C bond of interest: with the N+—O‐ bond oriented syn (gauche), the couplings are essentially as large as those in the parent amines, whereas with the N+—O‐ bond oriented anti, the couplings are about 4–5 Hz smaller. The 13C NMR chemical shifts of the N‐CH3 carbons, from which the configurations of the N‐epimeric amine oxides can be derived, are also reported.