Investigation of kukersite structure using NMR and oxidative cleavage: On the nature of phenolic precursors in the kerogen of Estonian kukersite

Abstract

Oxidative cleavage of Estonian kukersite kerogen, model 5-alkyl-1,3-benzenediols and their dialkyl ethers under alkaline KMnO4 and ruthenium ion catalyzed oxidation conditions, followed by CP/MAS 13C NMR and GC-MS studies of products, was carried out. Based on the stability of ether model compounds under alkaline KMnO4 oxidation conditions, full oxidizability of kerogen into low-molecular acidic products and similar carbon type composition of KMnO4 treated and intact kerogen, it was assumed that alkylbenzenediols are bound to the kerogen structure via cross-links in alkyl chains (and possibly via aryl-aliphatic monoether bonds as well). Location of free phenolic hydroxyl groups is determined by hydrogen bonds. Earlier determinations of "apparent" aryl-aliphatic ether bonds, using ether-cleaving HI and bulk AlBr3 reagents under severe conditions, were discussed and the action of trimethylsilyliodide and AlBr3 on the model compounds was examined as well.